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<li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">string</span></code> — Common string operations</a><ul>
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<section id="module-string">
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<span id="string-common-string-operations"></span><h1><code class="xref py py-mod docutils literal notranslate"><span class="pre">string</span></code> — Common string operations<a class="headerlink" href="#module-string" title="Link to this heading">¶</a></h1>
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<p><strong>Source code:</strong> <a class="extlink-source reference external" href="https://github.com/python/cpython/tree/3.13/Lib/string.py">Lib/string.py</a></p>
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<p class="admonition-title">See also</p>
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<p><a class="reference internal" href="stdtypes.html#textseq"><span class="std std-ref">Text Sequence Type — str</span></a></p>
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<p><a class="reference internal" href="stdtypes.html#string-methods"><span class="std std-ref">String Methods</span></a></p>
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<section id="string-constants">
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<h2>String constants<a class="headerlink" href="#string-constants" title="Link to this heading">¶</a></h2>
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<p>The constants defined in this module are:</p>
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<dl class="py data">
|
||
<dt class="sig sig-object py" id="string.ascii_letters">
|
||
<span class="sig-prename descclassname"><span class="pre">string.</span></span><span class="sig-name descname"><span class="pre">ascii_letters</span></span><a class="headerlink" href="#string.ascii_letters" title="Link to this definition">¶</a></dt>
|
||
<dd><p>The concatenation of the <a class="reference internal" href="#string.ascii_lowercase" title="string.ascii_lowercase"><code class="xref py py-const docutils literal notranslate"><span class="pre">ascii_lowercase</span></code></a> and <a class="reference internal" href="#string.ascii_uppercase" title="string.ascii_uppercase"><code class="xref py py-const docutils literal notranslate"><span class="pre">ascii_uppercase</span></code></a>
|
||
constants described below. This value is not locale-dependent.</p>
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</dd></dl>
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<dl class="py data">
|
||
<dt class="sig sig-object py" id="string.ascii_lowercase">
|
||
<span class="sig-prename descclassname"><span class="pre">string.</span></span><span class="sig-name descname"><span class="pre">ascii_lowercase</span></span><a class="headerlink" href="#string.ascii_lowercase" title="Link to this definition">¶</a></dt>
|
||
<dd><p>The lowercase letters <code class="docutils literal notranslate"><span class="pre">'abcdefghijklmnopqrstuvwxyz'</span></code>. This value is not
|
||
locale-dependent and will not change.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="py data">
|
||
<dt class="sig sig-object py" id="string.ascii_uppercase">
|
||
<span class="sig-prename descclassname"><span class="pre">string.</span></span><span class="sig-name descname"><span class="pre">ascii_uppercase</span></span><a class="headerlink" href="#string.ascii_uppercase" title="Link to this definition">¶</a></dt>
|
||
<dd><p>The uppercase letters <code class="docutils literal notranslate"><span class="pre">'ABCDEFGHIJKLMNOPQRSTUVWXYZ'</span></code>. This value is not
|
||
locale-dependent and will not change.</p>
|
||
</dd></dl>
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||
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<dl class="py data">
|
||
<dt class="sig sig-object py" id="string.digits">
|
||
<span class="sig-prename descclassname"><span class="pre">string.</span></span><span class="sig-name descname"><span class="pre">digits</span></span><a class="headerlink" href="#string.digits" title="Link to this definition">¶</a></dt>
|
||
<dd><p>The string <code class="docutils literal notranslate"><span class="pre">'0123456789'</span></code>.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="py data">
|
||
<dt class="sig sig-object py" id="string.hexdigits">
|
||
<span class="sig-prename descclassname"><span class="pre">string.</span></span><span class="sig-name descname"><span class="pre">hexdigits</span></span><a class="headerlink" href="#string.hexdigits" title="Link to this definition">¶</a></dt>
|
||
<dd><p>The string <code class="docutils literal notranslate"><span class="pre">'0123456789abcdefABCDEF'</span></code>.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="py data">
|
||
<dt class="sig sig-object py" id="string.octdigits">
|
||
<span class="sig-prename descclassname"><span class="pre">string.</span></span><span class="sig-name descname"><span class="pre">octdigits</span></span><a class="headerlink" href="#string.octdigits" title="Link to this definition">¶</a></dt>
|
||
<dd><p>The string <code class="docutils literal notranslate"><span class="pre">'01234567'</span></code>.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="py data">
|
||
<dt class="sig sig-object py" id="string.punctuation">
|
||
<span class="sig-prename descclassname"><span class="pre">string.</span></span><span class="sig-name descname"><span class="pre">punctuation</span></span><a class="headerlink" href="#string.punctuation" title="Link to this definition">¶</a></dt>
|
||
<dd><p>String of ASCII characters which are considered punctuation characters
|
||
in the <code class="docutils literal notranslate"><span class="pre">C</span></code> locale: <code class="docutils literal notranslate"><span class="pre">!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~</span></code>.</p>
|
||
</dd></dl>
|
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<dl class="py data">
|
||
<dt class="sig sig-object py" id="string.printable">
|
||
<span class="sig-prename descclassname"><span class="pre">string.</span></span><span class="sig-name descname"><span class="pre">printable</span></span><a class="headerlink" href="#string.printable" title="Link to this definition">¶</a></dt>
|
||
<dd><p>String of ASCII characters which are considered printable by Python.
|
||
This is a combination of <a class="reference internal" href="#string.digits" title="string.digits"><code class="xref py py-const docutils literal notranslate"><span class="pre">digits</span></code></a>, <a class="reference internal" href="#string.ascii_letters" title="string.ascii_letters"><code class="xref py py-const docutils literal notranslate"><span class="pre">ascii_letters</span></code></a>,
|
||
<a class="reference internal" href="#string.punctuation" title="string.punctuation"><code class="xref py py-const docutils literal notranslate"><span class="pre">punctuation</span></code></a>, and <a class="reference internal" href="#string.whitespace" title="string.whitespace"><code class="xref py py-const docutils literal notranslate"><span class="pre">whitespace</span></code></a>.</p>
|
||
<div class="admonition note">
|
||
<p class="admonition-title">Note</p>
|
||
<p>By design, <a class="reference internal" href="stdtypes.html#str.isprintable" title="str.isprintable"><code class="xref py py-meth docutils literal notranslate"><span class="pre">string.printable.isprintable()</span></code></a>
|
||
returns <a class="reference internal" href="constants.html#False" title="False"><code class="xref py py-const docutils literal notranslate"><span class="pre">False</span></code></a>. In particular, <code class="docutils literal notranslate"><span class="pre">string.printable</span></code> is not
|
||
printable in the POSIX sense (see <em class="manpage"><a class="manpage reference external" href="https://manpages.debian.org/locale(5)">LC_CTYPE</a></em>).</p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="py data">
|
||
<dt class="sig sig-object py" id="string.whitespace">
|
||
<span class="sig-prename descclassname"><span class="pre">string.</span></span><span class="sig-name descname"><span class="pre">whitespace</span></span><a class="headerlink" href="#string.whitespace" title="Link to this definition">¶</a></dt>
|
||
<dd><p>A string containing all ASCII characters that are considered whitespace.
|
||
This includes the characters space, tab, linefeed, return, formfeed, and
|
||
vertical tab.</p>
|
||
</dd></dl>
|
||
|
||
</section>
|
||
<section id="custom-string-formatting">
|
||
<span id="string-formatting"></span><h2>Custom String Formatting<a class="headerlink" href="#custom-string-formatting" title="Link to this heading">¶</a></h2>
|
||
<p>The built-in string class provides the ability to do complex variable
|
||
substitutions and value formatting via the <a class="reference internal" href="stdtypes.html#str.format" title="str.format"><code class="xref py py-meth docutils literal notranslate"><span class="pre">format()</span></code></a> method described in
|
||
<span class="target" id="index-0"></span><a class="pep reference external" href="https://peps.python.org/pep-3101/"><strong>PEP 3101</strong></a>. The <a class="reference internal" href="#string.Formatter" title="string.Formatter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Formatter</span></code></a> class in the <a class="reference internal" href="#module-string" title="string: Common string operations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">string</span></code></a> module allows
|
||
you to create and customize your own string formatting behaviors using the same
|
||
implementation as the built-in <a class="reference internal" href="stdtypes.html#str.format" title="str.format"><code class="xref py py-meth docutils literal notranslate"><span class="pre">format()</span></code></a> method.</p>
|
||
<dl class="py class">
|
||
<dt class="sig sig-object py" id="string.Formatter">
|
||
<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">string.</span></span><span class="sig-name descname"><span class="pre">Formatter</span></span><a class="headerlink" href="#string.Formatter" title="Link to this definition">¶</a></dt>
|
||
<dd><p>The <a class="reference internal" href="#string.Formatter" title="string.Formatter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Formatter</span></code></a> class has the following public methods:</p>
|
||
<dl class="py method">
|
||
<dt class="sig sig-object py" id="string.Formatter.format">
|
||
<span class="sig-name descname"><span class="pre">format</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">format_string</span></span></em>, <em class="sig-param"><span class="positional-only-separator o"><abbr title="Positional-only parameter separator (PEP 570)"><span class="pre">/</span></abbr></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">**</span></span><span class="n"><span class="pre">kwargs</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#string.Formatter.format" title="Link to this definition">¶</a></dt>
|
||
<dd><p>The primary API method. It takes a format string and
|
||
an arbitrary set of positional and keyword arguments.
|
||
It is just a wrapper that calls <a class="reference internal" href="#string.Formatter.vformat" title="string.Formatter.vformat"><code class="xref py py-meth docutils literal notranslate"><span class="pre">vformat()</span></code></a>.</p>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.7: </span>A format string argument is now <a class="reference internal" href="../glossary.html#positional-only-parameter"><span class="std std-ref">positional-only</span></a>.</p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="py method">
|
||
<dt class="sig sig-object py" id="string.Formatter.vformat">
|
||
<span class="sig-name descname"><span class="pre">vformat</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">format_string</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">kwargs</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#string.Formatter.vformat" title="Link to this definition">¶</a></dt>
|
||
<dd><p>This function does the actual work of formatting. It is exposed as a
|
||
separate function for cases where you want to pass in a predefined
|
||
dictionary of arguments, rather than unpacking and repacking the
|
||
dictionary as individual arguments using the <code class="docutils literal notranslate"><span class="pre">*args</span></code> and <code class="docutils literal notranslate"><span class="pre">**kwargs</span></code>
|
||
syntax. <a class="reference internal" href="#string.Formatter.vformat" title="string.Formatter.vformat"><code class="xref py py-meth docutils literal notranslate"><span class="pre">vformat()</span></code></a> does the work of breaking up the format string
|
||
into character data and replacement fields. It calls the various
|
||
methods described below.</p>
|
||
</dd></dl>
|
||
|
||
<p>In addition, the <a class="reference internal" href="#string.Formatter" title="string.Formatter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Formatter</span></code></a> defines a number of methods that are
|
||
intended to be replaced by subclasses:</p>
|
||
<dl class="py method">
|
||
<dt class="sig sig-object py" id="string.Formatter.parse">
|
||
<span class="sig-name descname"><span class="pre">parse</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">format_string</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#string.Formatter.parse" title="Link to this definition">¶</a></dt>
|
||
<dd><p>Loop over the format_string and return an iterable of tuples
|
||
(<em>literal_text</em>, <em>field_name</em>, <em>format_spec</em>, <em>conversion</em>). This is used
|
||
by <a class="reference internal" href="#string.Formatter.vformat" title="string.Formatter.vformat"><code class="xref py py-meth docutils literal notranslate"><span class="pre">vformat()</span></code></a> to break the string into either literal text, or
|
||
replacement fields.</p>
|
||
<p>The values in the tuple conceptually represent a span of literal text
|
||
followed by a single replacement field. If there is no literal text
|
||
(which can happen if two replacement fields occur consecutively), then
|
||
<em>literal_text</em> will be a zero-length string. If there is no replacement
|
||
field, then the values of <em>field_name</em>, <em>format_spec</em> and <em>conversion</em>
|
||
will be <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="py method">
|
||
<dt class="sig sig-object py" id="string.Formatter.get_field">
|
||
<span class="sig-name descname"><span class="pre">get_field</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">field_name</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">kwargs</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#string.Formatter.get_field" title="Link to this definition">¶</a></dt>
|
||
<dd><p>Given <em>field_name</em> as returned by <a class="reference internal" href="#string.Formatter.parse" title="string.Formatter.parse"><code class="xref py py-meth docutils literal notranslate"><span class="pre">parse()</span></code></a> (see above), convert it to
|
||
an object to be formatted. Returns a tuple (obj, used_key). The default
|
||
version takes strings of the form defined in <span class="target" id="index-1"></span><a class="pep reference external" href="https://peps.python.org/pep-3101/"><strong>PEP 3101</strong></a>, such as
|
||
“0[name]” or “label.title”. <em>args</em> and <em>kwargs</em> are as passed in to
|
||
<a class="reference internal" href="#string.Formatter.vformat" title="string.Formatter.vformat"><code class="xref py py-meth docutils literal notranslate"><span class="pre">vformat()</span></code></a>. The return value <em>used_key</em> has the same meaning as the
|
||
<em>key</em> parameter to <a class="reference internal" href="#string.Formatter.get_value" title="string.Formatter.get_value"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get_value()</span></code></a>.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="py method">
|
||
<dt class="sig sig-object py" id="string.Formatter.get_value">
|
||
<span class="sig-name descname"><span class="pre">get_value</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">key</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">kwargs</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#string.Formatter.get_value" title="Link to this definition">¶</a></dt>
|
||
<dd><p>Retrieve a given field value. The <em>key</em> argument will be either an
|
||
integer or a string. If it is an integer, it represents the index of the
|
||
positional argument in <em>args</em>; if it is a string, then it represents a
|
||
named argument in <em>kwargs</em>.</p>
|
||
<p>The <em>args</em> parameter is set to the list of positional arguments to
|
||
<a class="reference internal" href="#string.Formatter.vformat" title="string.Formatter.vformat"><code class="xref py py-meth docutils literal notranslate"><span class="pre">vformat()</span></code></a>, and the <em>kwargs</em> parameter is set to the dictionary of
|
||
keyword arguments.</p>
|
||
<p>For compound field names, these functions are only called for the first
|
||
component of the field name; subsequent components are handled through
|
||
normal attribute and indexing operations.</p>
|
||
<p>So for example, the field expression ‘0.name’ would cause
|
||
<a class="reference internal" href="#string.Formatter.get_value" title="string.Formatter.get_value"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get_value()</span></code></a> to be called with a <em>key</em> argument of 0. The <code class="docutils literal notranslate"><span class="pre">name</span></code>
|
||
attribute will be looked up after <a class="reference internal" href="#string.Formatter.get_value" title="string.Formatter.get_value"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get_value()</span></code></a> returns by calling the
|
||
built-in <a class="reference internal" href="functions.html#getattr" title="getattr"><code class="xref py py-func docutils literal notranslate"><span class="pre">getattr()</span></code></a> function.</p>
|
||
<p>If the index or keyword refers to an item that does not exist, then an
|
||
<a class="reference internal" href="exceptions.html#IndexError" title="IndexError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">IndexError</span></code></a> or <a class="reference internal" href="exceptions.html#KeyError" title="KeyError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">KeyError</span></code></a> should be raised.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="py method">
|
||
<dt class="sig sig-object py" id="string.Formatter.check_unused_args">
|
||
<span class="sig-name descname"><span class="pre">check_unused_args</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">used_args</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">kwargs</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#string.Formatter.check_unused_args" title="Link to this definition">¶</a></dt>
|
||
<dd><p>Implement checking for unused arguments if desired. The arguments to this
|
||
function is the set of all argument keys that were actually referred to in
|
||
the format string (integers for positional arguments, and strings for
|
||
named arguments), and a reference to the <em>args</em> and <em>kwargs</em> that was
|
||
passed to vformat. The set of unused args can be calculated from these
|
||
parameters. <a class="reference internal" href="#string.Formatter.check_unused_args" title="string.Formatter.check_unused_args"><code class="xref py py-meth docutils literal notranslate"><span class="pre">check_unused_args()</span></code></a> is assumed to raise an exception if
|
||
the check fails.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="py method">
|
||
<dt class="sig sig-object py" id="string.Formatter.format_field">
|
||
<span class="sig-name descname"><span class="pre">format_field</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">value</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">format_spec</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#string.Formatter.format_field" title="Link to this definition">¶</a></dt>
|
||
<dd><p><a class="reference internal" href="#string.Formatter.format_field" title="string.Formatter.format_field"><code class="xref py py-meth docutils literal notranslate"><span class="pre">format_field()</span></code></a> simply calls the global <a class="reference internal" href="functions.html#format" title="format"><code class="xref py py-func docutils literal notranslate"><span class="pre">format()</span></code></a> built-in. The
|
||
method is provided so that subclasses can override it.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="py method">
|
||
<dt class="sig sig-object py" id="string.Formatter.convert_field">
|
||
<span class="sig-name descname"><span class="pre">convert_field</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">value</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">conversion</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#string.Formatter.convert_field" title="Link to this definition">¶</a></dt>
|
||
<dd><p>Converts the value (returned by <a class="reference internal" href="#string.Formatter.get_field" title="string.Formatter.get_field"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get_field()</span></code></a>) given a conversion type
|
||
(as in the tuple returned by the <a class="reference internal" href="#string.Formatter.parse" title="string.Formatter.parse"><code class="xref py py-meth docutils literal notranslate"><span class="pre">parse()</span></code></a> method). The default
|
||
version understands ‘s’ (str), ‘r’ (repr) and ‘a’ (ascii) conversion
|
||
types.</p>
|
||
</dd></dl>
|
||
|
||
</dd></dl>
|
||
|
||
</section>
|
||
<section id="format-string-syntax">
|
||
<span id="formatstrings"></span><h2>Format String Syntax<a class="headerlink" href="#format-string-syntax" title="Link to this heading">¶</a></h2>
|
||
<p>The <a class="reference internal" href="stdtypes.html#str.format" title="str.format"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.format()</span></code></a> method and the <a class="reference internal" href="#string.Formatter" title="string.Formatter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Formatter</span></code></a> class share the same
|
||
syntax for format strings (although in the case of <a class="reference internal" href="#string.Formatter" title="string.Formatter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Formatter</span></code></a>,
|
||
subclasses can define their own format string syntax). The syntax is
|
||
related to that of <a class="reference internal" href="../reference/lexical_analysis.html#f-strings"><span class="std std-ref">formatted string literals</span></a>, but it is
|
||
less sophisticated and, in particular, does not support arbitrary expressions.</p>
|
||
<p id="index-2">Format strings contain “replacement fields” surrounded by curly braces <code class="docutils literal notranslate"><span class="pre">{}</span></code>.
|
||
Anything that is not contained in braces is considered literal text, which is
|
||
copied unchanged to the output. If you need to include a brace character in the
|
||
literal text, it can be escaped by doubling: <code class="docutils literal notranslate"><span class="pre">{{</span></code> and <code class="docutils literal notranslate"><span class="pre">}}</span></code>.</p>
|
||
<p>The grammar for a replacement field is as follows:</p>
|
||
<pre>
|
||
<strong id="grammar-token-format-string-replacement_field">replacement_field</strong> ::= "{" [<a class="reference internal" href="#grammar-token-format-string-field_name"><code class="xref docutils literal notranslate"><span class="pre">field_name</span></code></a>] ["!" <a class="reference internal" href="#grammar-token-format-string-conversion"><code class="xref docutils literal notranslate"><span class="pre">conversion</span></code></a>] [":" <a class="reference internal" href="#grammar-token-format-string-format_spec"><code class="xref docutils literal notranslate"><span class="pre">format_spec</span></code></a>] "}"
|
||
<strong id="grammar-token-format-string-field_name">field_name</strong> ::= <a class="reference internal" href="#grammar-token-format-string-arg_name"><code class="xref docutils literal notranslate"><span class="pre">arg_name</span></code></a> ("." <a class="reference internal" href="#grammar-token-format-string-attribute_name"><code class="xref docutils literal notranslate"><span class="pre">attribute_name</span></code></a> | "[" <a class="reference internal" href="#grammar-token-format-string-element_index"><code class="xref docutils literal notranslate"><span class="pre">element_index</span></code></a> "]")*
|
||
<strong id="grammar-token-format-string-arg_name">arg_name</strong> ::= [<a class="reference internal" href="../reference/lexical_analysis.html#grammar-token-python-grammar-identifier"><code class="xref docutils literal notranslate"><span class="pre">identifier</span></code></a> | <a class="reference internal" href="../reference/lexical_analysis.html#grammar-token-python-grammar-digit"><code class="xref docutils literal notranslate"><span class="pre">digit</span></code></a>+]
|
||
<strong id="grammar-token-format-string-attribute_name">attribute_name</strong> ::= <a class="reference internal" href="../reference/lexical_analysis.html#grammar-token-python-grammar-identifier"><code class="xref docutils literal notranslate"><span class="pre">identifier</span></code></a>
|
||
<strong id="grammar-token-format-string-element_index">element_index</strong> ::= <a class="reference internal" href="../reference/lexical_analysis.html#grammar-token-python-grammar-digit"><code class="xref docutils literal notranslate"><span class="pre">digit</span></code></a>+ | <a class="reference internal" href="#grammar-token-format-string-index_string"><code class="xref docutils literal notranslate"><span class="pre">index_string</span></code></a>
|
||
<strong id="grammar-token-format-string-index_string">index_string</strong> ::= <any source character except "]"> +
|
||
<strong id="grammar-token-format-string-conversion">conversion</strong> ::= "r" | "s" | "a"
|
||
<strong id="grammar-token-format-string-format_spec">format_spec</strong> ::= <a class="reference internal" href="#grammar-token-format-spec-format_spec"><code class="xref docutils literal notranslate"><span class="pre">format-spec:format_spec</span></code></a>
|
||
</pre>
|
||
<p>In less formal terms, the replacement field can start with a <em>field_name</em> that specifies
|
||
the object whose value is to be formatted and inserted
|
||
into the output instead of the replacement field.
|
||
The <em>field_name</em> is optionally followed by a <em>conversion</em> field, which is
|
||
preceded by an exclamation point <code class="docutils literal notranslate"><span class="pre">'!'</span></code>, and a <em>format_spec</em>, which is preceded
|
||
by a colon <code class="docutils literal notranslate"><span class="pre">':'</span></code>. These specify a non-default format for the replacement value.</p>
|
||
<p>See also the <a class="reference internal" href="#formatspec"><span class="std std-ref">Format Specification Mini-Language</span></a> section.</p>
|
||
<p>The <em>field_name</em> itself begins with an <em>arg_name</em> that is either a number or a
|
||
keyword. If it’s a number, it refers to a positional argument, and if it’s a keyword,
|
||
it refers to a named keyword argument. An <em>arg_name</em> is treated as a number if
|
||
a call to <a class="reference internal" href="stdtypes.html#str.isdecimal" title="str.isdecimal"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.isdecimal()</span></code></a> on the string would return true.
|
||
If the numerical arg_names in a format string
|
||
are 0, 1, 2, … in sequence, they can all be omitted (not just some)
|
||
and the numbers 0, 1, 2, … will be automatically inserted in that order.
|
||
Because <em>arg_name</em> is not quote-delimited, it is not possible to specify arbitrary
|
||
dictionary keys (e.g., the strings <code class="docutils literal notranslate"><span class="pre">'10'</span></code> or <code class="docutils literal notranslate"><span class="pre">':-]'</span></code>) within a format string.
|
||
The <em>arg_name</em> can be followed by any number of index or
|
||
attribute expressions. An expression of the form <code class="docutils literal notranslate"><span class="pre">'.name'</span></code> selects the named
|
||
attribute using <a class="reference internal" href="functions.html#getattr" title="getattr"><code class="xref py py-func docutils literal notranslate"><span class="pre">getattr()</span></code></a>, while an expression of the form <code class="docutils literal notranslate"><span class="pre">'[index]'</span></code>
|
||
does an index lookup using <a class="reference internal" href="../reference/datamodel.html#object.__getitem__" title="object.__getitem__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__getitem__()</span></code></a>.</p>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.1: </span>The positional argument specifiers can be omitted for <a class="reference internal" href="stdtypes.html#str.format" title="str.format"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.format()</span></code></a>,
|
||
so <code class="docutils literal notranslate"><span class="pre">'{}</span> <span class="pre">{}'.format(a,</span> <span class="pre">b)</span></code> is equivalent to <code class="docutils literal notranslate"><span class="pre">'{0}</span> <span class="pre">{1}'.format(a,</span> <span class="pre">b)</span></code>.</p>
|
||
</div>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.4: </span>The positional argument specifiers can be omitted for <a class="reference internal" href="#string.Formatter" title="string.Formatter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Formatter</span></code></a>.</p>
|
||
</div>
|
||
<p>Some simple format string examples:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="s2">"First, thou shalt count to </span><span class="si">{0}</span><span class="s2">"</span> <span class="c1"># References first positional argument</span>
|
||
<span class="s2">"Bring me a </span><span class="si">{}</span><span class="s2">"</span> <span class="c1"># Implicitly references the first positional argument</span>
|
||
<span class="s2">"From </span><span class="si">{}</span><span class="s2"> to </span><span class="si">{}</span><span class="s2">"</span> <span class="c1"># Same as "From {0} to {1}"</span>
|
||
<span class="s2">"My quest is </span><span class="si">{name}</span><span class="s2">"</span> <span class="c1"># References keyword argument 'name'</span>
|
||
<span class="s2">"Weight in tons </span><span class="si">{0.weight}</span><span class="s2">"</span> <span class="c1"># 'weight' attribute of first positional arg</span>
|
||
<span class="s2">"Units destroyed: </span><span class="si">{players[0]}</span><span class="s2">"</span> <span class="c1"># First element of keyword argument 'players'.</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>The <em>conversion</em> field causes a type coercion before formatting. Normally, the
|
||
job of formatting a value is done by the <a class="reference internal" href="../reference/datamodel.html#object.__format__" title="object.__format__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__format__()</span></code></a> method of the value
|
||
itself. However, in some cases it is desirable to force a type to be formatted
|
||
as a string, overriding its own definition of formatting. By converting the
|
||
value to a string before calling <a class="reference internal" href="../reference/datamodel.html#object.__format__" title="object.__format__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__format__()</span></code></a>, the normal formatting logic
|
||
is bypassed.</p>
|
||
<p>Three conversion flags are currently supported: <code class="docutils literal notranslate"><span class="pre">'!s'</span></code> which calls <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-func docutils literal notranslate"><span class="pre">str()</span></code></a>
|
||
on the value, <code class="docutils literal notranslate"><span class="pre">'!r'</span></code> which calls <a class="reference internal" href="functions.html#repr" title="repr"><code class="xref py py-func docutils literal notranslate"><span class="pre">repr()</span></code></a> and <code class="docutils literal notranslate"><span class="pre">'!a'</span></code> which calls
|
||
<a class="reference internal" href="functions.html#ascii" title="ascii"><code class="xref py py-func docutils literal notranslate"><span class="pre">ascii()</span></code></a>.</p>
|
||
<p>Some examples:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="s2">"Harold's a clever </span><span class="si">{0!s}</span><span class="s2">"</span> <span class="c1"># Calls str() on the argument first</span>
|
||
<span class="s2">"Bring out the holy </span><span class="si">{name!r}</span><span class="s2">"</span> <span class="c1"># Calls repr() on the argument first</span>
|
||
<span class="s2">"More </span><span class="si">{!a}</span><span class="s2">"</span> <span class="c1"># Calls ascii() on the argument first</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>The <em>format_spec</em> field contains a specification of how the value should be
|
||
presented, including such details as field width, alignment, padding, decimal
|
||
precision and so on. Each value type can define its own “formatting
|
||
mini-language” or interpretation of the <em>format_spec</em>.</p>
|
||
<p>Most built-in types support a common formatting mini-language, which is
|
||
described in the next section.</p>
|
||
<p>A <em>format_spec</em> field can also include nested replacement fields within it.
|
||
These nested replacement fields may contain a field name, conversion flag
|
||
and format specification, but deeper nesting is
|
||
not allowed. The replacement fields within the
|
||
format_spec are substituted before the <em>format_spec</em> string is interpreted.
|
||
This allows the formatting of a value to be dynamically specified.</p>
|
||
<p>See the <a class="reference internal" href="#formatexamples"><span class="std std-ref">Format examples</span></a> section for some examples.</p>
|
||
<section id="format-specification-mini-language">
|
||
<span id="formatspec"></span><h3>Format Specification Mini-Language<a class="headerlink" href="#format-specification-mini-language" title="Link to this heading">¶</a></h3>
|
||
<p>“Format specifications” are used within replacement fields contained within a
|
||
format string to define how individual values are presented (see
|
||
<a class="reference internal" href="#formatstrings"><span class="std std-ref">Format String Syntax</span></a> and <a class="reference internal" href="../reference/lexical_analysis.html#f-strings"><span class="std std-ref">f-strings</span></a>).
|
||
They can also be passed directly to the built-in
|
||
<a class="reference internal" href="functions.html#format" title="format"><code class="xref py py-func docutils literal notranslate"><span class="pre">format()</span></code></a> function. Each formattable type may define how the format
|
||
specification is to be interpreted.</p>
|
||
<p>Most built-in types implement the following options for format specifications,
|
||
although some of the formatting options are only supported by the numeric types.</p>
|
||
<p>A general convention is that an empty format specification produces
|
||
the same result as if you had called <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-func docutils literal notranslate"><span class="pre">str()</span></code></a> on the value. A
|
||
non-empty format specification typically modifies the result.</p>
|
||
<p>The general form of a <em>standard format specifier</em> is:</p>
|
||
<pre>
|
||
<strong id="grammar-token-format-spec-format_spec">format_spec</strong> ::= [<a class="reference internal" href="#grammar-token-format-spec-options"><code class="xref docutils literal notranslate"><span class="pre">options</span></code></a>][<a class="reference internal" href="#grammar-token-format-spec-width"><code class="xref docutils literal notranslate"><span class="pre">width</span></code></a>][<a class="reference internal" href="#grammar-token-format-spec-grouping"><code class="xref docutils literal notranslate"><span class="pre">grouping</span></code></a>]["." <a class="reference internal" href="#grammar-token-format-spec-precision"><code class="xref docutils literal notranslate"><span class="pre">precision</span></code></a>][<a class="reference internal" href="#grammar-token-format-spec-type"><code class="xref docutils literal notranslate"><span class="pre">type</span></code></a>]
|
||
<strong id="grammar-token-format-spec-options">options</strong> ::= [[<a class="reference internal" href="#grammar-token-format-spec-fill"><code class="xref docutils literal notranslate"><span class="pre">fill</span></code></a>]<a class="reference internal" href="#grammar-token-format-spec-align"><code class="xref docutils literal notranslate"><span class="pre">align</span></code></a>][<a class="reference internal" href="#grammar-token-format-spec-sign"><code class="xref docutils literal notranslate"><span class="pre">sign</span></code></a>]["z"]["#"]["0"]
|
||
<strong id="grammar-token-format-spec-fill">fill</strong> ::= <any character>
|
||
<strong id="grammar-token-format-spec-align">align</strong> ::= "<" | ">" | "=" | "^"
|
||
<strong id="grammar-token-format-spec-sign">sign</strong> ::= "+" | "-" | " "
|
||
<strong id="grammar-token-format-spec-width">width</strong> ::= <a class="reference internal" href="../reference/lexical_analysis.html#grammar-token-python-grammar-digit"><code class="xref docutils literal notranslate"><span class="pre">digit</span></code></a>+
|
||
<strong id="grammar-token-format-spec-grouping">grouping</strong> ::= "," | "_"
|
||
<strong id="grammar-token-format-spec-precision">precision</strong> ::= <a class="reference internal" href="../reference/lexical_analysis.html#grammar-token-python-grammar-digit"><code class="xref docutils literal notranslate"><span class="pre">digit</span></code></a>+
|
||
<strong id="grammar-token-format-spec-type">type</strong> ::= "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g"
|
||
| "G" | "n" | "o" | "s" | "x" | "X" | "%"
|
||
</pre>
|
||
<p>If a valid <em>align</em> value is specified, it can be preceded by a <em>fill</em>
|
||
character that can be any character and defaults to a space if omitted.
|
||
It is not possible to use a literal curly brace (”<code class="docutils literal notranslate"><span class="pre">{</span></code>” or “<code class="docutils literal notranslate"><span class="pre">}</span></code>”) as
|
||
the <em>fill</em> character in a <a class="reference internal" href="../reference/lexical_analysis.html#f-strings"><span class="std std-ref">formatted string literal</span></a> or when using the <a class="reference internal" href="stdtypes.html#str.format" title="str.format"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.format()</span></code></a>
|
||
method. However, it is possible to insert a curly brace
|
||
with a nested replacement field. This limitation doesn’t
|
||
affect the <a class="reference internal" href="functions.html#format" title="format"><code class="xref py py-func docutils literal notranslate"><span class="pre">format()</span></code></a> function.</p>
|
||
<p>The meaning of the various alignment options is as follows:</p>
|
||
<table class="docutils align-default" id="index-3">
|
||
<thead>
|
||
<tr class="row-odd"><th class="head"><p>Option</p></th>
|
||
<th class="head"><p>Meaning</p></th>
|
||
</tr>
|
||
</thead>
|
||
<tbody>
|
||
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'<'</span></code></p></td>
|
||
<td><p>Forces the field to be left-aligned within the available
|
||
space (this is the default for most objects).</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'>'</span></code></p></td>
|
||
<td><p>Forces the field to be right-aligned within the
|
||
available space (this is the default for numbers).</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'='</span></code></p></td>
|
||
<td><p>Forces the padding to be placed after the sign (if any)
|
||
but before the digits. This is used for printing fields
|
||
in the form ‘+000000120’. This alignment option is only
|
||
valid for numeric types, excluding <a class="reference internal" href="functions.html#complex" title="complex"><code class="xref py py-class docutils literal notranslate"><span class="pre">complex</span></code></a>.
|
||
It becomes the default for numbers when ‘0’ immediately
|
||
precedes the field width.</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'^'</span></code></p></td>
|
||
<td><p>Forces the field to be centered within the available
|
||
space.</p></td>
|
||
</tr>
|
||
</tbody>
|
||
</table>
|
||
<p>Note that unless a minimum field width is defined, the field width will always
|
||
be the same size as the data to fill it, so that the alignment option has no
|
||
meaning in this case.</p>
|
||
<p>The <em>sign</em> option is only valid for number types, and can be one of the
|
||
following:</p>
|
||
<table class="docutils align-default" id="index-4">
|
||
<thead>
|
||
<tr class="row-odd"><th class="head"><p>Option</p></th>
|
||
<th class="head"><p>Meaning</p></th>
|
||
</tr>
|
||
</thead>
|
||
<tbody>
|
||
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'+'</span></code></p></td>
|
||
<td><p>Indicates that a sign should be used for both
|
||
positive as well as negative numbers.</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'-'</span></code></p></td>
|
||
<td><p>Indicates that a sign should be used only for negative
|
||
numbers (this is the default behavior).</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p>space</p></td>
|
||
<td><p>Indicates that a leading space should be used on
|
||
positive numbers, and a minus sign on negative numbers.</p></td>
|
||
</tr>
|
||
</tbody>
|
||
</table>
|
||
<p id="index-5">The <code class="docutils literal notranslate"><span class="pre">'z'</span></code> option coerces negative zero floating-point values to positive
|
||
zero after rounding to the format precision. This option is only valid for
|
||
floating-point presentation types.</p>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.11: </span>Added the <code class="docutils literal notranslate"><span class="pre">'z'</span></code> option (see also <span class="target" id="index-6"></span><a class="pep reference external" href="https://peps.python.org/pep-0682/"><strong>PEP 682</strong></a>).</p>
|
||
</div>
|
||
<p id="index-7">The <code class="docutils literal notranslate"><span class="pre">'#'</span></code> option causes the “alternate form” to be used for the
|
||
conversion. The alternate form is defined differently for different
|
||
types. This option is only valid for integer, float and complex
|
||
types. For integers, when binary, octal, or hexadecimal output
|
||
is used, this option adds the respective prefix <code class="docutils literal notranslate"><span class="pre">'0b'</span></code>, <code class="docutils literal notranslate"><span class="pre">'0o'</span></code>,
|
||
<code class="docutils literal notranslate"><span class="pre">'0x'</span></code>, or <code class="docutils literal notranslate"><span class="pre">'0X'</span></code> to the output value. For float and complex the
|
||
alternate form causes the result of the conversion to always contain a
|
||
decimal-point character, even if no digits follow it. Normally, a
|
||
decimal-point character appears in the result of these conversions
|
||
only if a digit follows it. In addition, for <code class="docutils literal notranslate"><span class="pre">'g'</span></code> and <code class="docutils literal notranslate"><span class="pre">'G'</span></code>
|
||
conversions, trailing zeros are not removed from the result.</p>
|
||
<p>The <em>width</em> is a decimal integer defining the minimum total field width,
|
||
including any prefixes, separators, and other formatting characters.
|
||
If not specified, then the field width will be determined by the content.</p>
|
||
<p>When no explicit alignment is given, preceding the <em>width</em> field by a zero
|
||
(<code class="docutils literal notranslate"><span class="pre">'0'</span></code>) character enables sign-aware zero-padding for numeric types,
|
||
excluding <a class="reference internal" href="functions.html#complex" title="complex"><code class="xref py py-class docutils literal notranslate"><span class="pre">complex</span></code></a>. This is equivalent to a <em>fill</em> character of
|
||
<code class="docutils literal notranslate"><span class="pre">'0'</span></code> with an <em>alignment</em> type of <code class="docutils literal notranslate"><span class="pre">'='</span></code>.</p>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.10: </span>Preceding the <em>width</em> field by <code class="docutils literal notranslate"><span class="pre">'0'</span></code> no longer affects the default
|
||
alignment for strings.</p>
|
||
</div>
|
||
<p>The <em>grouping</em> option after the <em>width</em> field specifies
|
||
a digit group separator for the integral part of a number.
|
||
It can be one of the following:</p>
|
||
<table class="docutils align-default" id="index-8">
|
||
<thead>
|
||
<tr class="row-odd"><th class="head"><p>Option</p></th>
|
||
<th class="head"><p>Meaning</p></th>
|
||
</tr>
|
||
</thead>
|
||
<tbody>
|
||
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">','</span></code></p></td>
|
||
<td><p>Inserts a comma every 3 digits for
|
||
integer presentation type <code class="docutils literal notranslate"><span class="pre">'d'</span></code> and
|
||
floating-point presentation types, excluding <code class="docutils literal notranslate"><span class="pre">'n'</span></code>.
|
||
For other presentation types,
|
||
this option is not supported.</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'_'</span></code></p></td>
|
||
<td><p>Inserts an underscore every 3 digits for
|
||
integer presentation type <code class="docutils literal notranslate"><span class="pre">'d'</span></code> and
|
||
floating-point presentation types, excluding <code class="docutils literal notranslate"><span class="pre">'n'</span></code>.
|
||
For integer presentation types
|
||
<code class="docutils literal notranslate"><span class="pre">'b'</span></code>, <code class="docutils literal notranslate"><span class="pre">'o'</span></code>, <code class="docutils literal notranslate"><span class="pre">'x'</span></code>, and <code class="docutils literal notranslate"><span class="pre">'X'</span></code>,
|
||
underscores are inserted every 4 digits.
|
||
For other presentation types,
|
||
this option is not supported.</p></td>
|
||
</tr>
|
||
</tbody>
|
||
</table>
|
||
<p>For a locale aware separator, use the <code class="docutils literal notranslate"><span class="pre">'n'</span></code> presentation type instead.</p>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.1: </span>Added the <code class="docutils literal notranslate"><span class="pre">','</span></code> option (see also <span class="target" id="index-9"></span><a class="pep reference external" href="https://peps.python.org/pep-0378/"><strong>PEP 378</strong></a>).</p>
|
||
</div>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.6: </span>Added the <code class="docutils literal notranslate"><span class="pre">'_'</span></code> option (see also <span class="target" id="index-10"></span><a class="pep reference external" href="https://peps.python.org/pep-0515/"><strong>PEP 515</strong></a>).</p>
|
||
</div>
|
||
<p>The <em>precision</em> is a decimal integer indicating how many digits should be
|
||
displayed after the decimal point for presentation types
|
||
<code class="docutils literal notranslate"><span class="pre">'f'</span></code> and <code class="docutils literal notranslate"><span class="pre">'F'</span></code>, or before and after the decimal point for presentation
|
||
types <code class="docutils literal notranslate"><span class="pre">'g'</span></code> or <code class="docutils literal notranslate"><span class="pre">'G'</span></code>. For string presentation types the field
|
||
indicates the maximum field size - in other words, how many characters will be
|
||
used from the field content. The <em>precision</em> is not allowed for integer
|
||
presentation types.</p>
|
||
<p>Finally, the <em>type</em> determines how the data should be presented.</p>
|
||
<p>The available string presentation types are:</p>
|
||
<blockquote>
|
||
<div><table class="docutils align-default">
|
||
<thead>
|
||
<tr class="row-odd"><th class="head"><p>Type</p></th>
|
||
<th class="head"><p>Meaning</p></th>
|
||
</tr>
|
||
</thead>
|
||
<tbody>
|
||
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'s'</span></code></p></td>
|
||
<td><p>String format. This is the default type for strings and
|
||
may be omitted.</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p>None</p></td>
|
||
<td><p>The same as <code class="docutils literal notranslate"><span class="pre">'s'</span></code>.</p></td>
|
||
</tr>
|
||
</tbody>
|
||
</table>
|
||
</div></blockquote>
|
||
<p>The available integer presentation types are:</p>
|
||
<blockquote>
|
||
<div><table class="docutils align-default">
|
||
<thead>
|
||
<tr class="row-odd"><th class="head"><p>Type</p></th>
|
||
<th class="head"><p>Meaning</p></th>
|
||
</tr>
|
||
</thead>
|
||
<tbody>
|
||
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'b'</span></code></p></td>
|
||
<td><p>Binary format. Outputs the number in base 2.</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'c'</span></code></p></td>
|
||
<td><p>Character. Converts the integer to the corresponding
|
||
unicode character before printing.</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'d'</span></code></p></td>
|
||
<td><p>Decimal Integer. Outputs the number in base 10.</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'o'</span></code></p></td>
|
||
<td><p>Octal format. Outputs the number in base 8.</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'x'</span></code></p></td>
|
||
<td><p>Hex format. Outputs the number in base 16, using
|
||
lower-case letters for the digits above 9.</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'X'</span></code></p></td>
|
||
<td><p>Hex format. Outputs the number in base 16, using
|
||
upper-case letters for the digits above 9.
|
||
In case <code class="docutils literal notranslate"><span class="pre">'#'</span></code> is specified, the prefix <code class="docutils literal notranslate"><span class="pre">'0x'</span></code> will
|
||
be upper-cased to <code class="docutils literal notranslate"><span class="pre">'0X'</span></code> as well.</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'n'</span></code></p></td>
|
||
<td><p>Number. This is the same as <code class="docutils literal notranslate"><span class="pre">'d'</span></code>, except that it uses
|
||
the current locale setting to insert the appropriate
|
||
digit group separators.</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p>None</p></td>
|
||
<td><p>The same as <code class="docutils literal notranslate"><span class="pre">'d'</span></code>.</p></td>
|
||
</tr>
|
||
</tbody>
|
||
</table>
|
||
</div></blockquote>
|
||
<p>In addition to the above presentation types, integers can be formatted
|
||
with the floating-point presentation types listed below (except
|
||
<code class="docutils literal notranslate"><span class="pre">'n'</span></code> and <code class="docutils literal notranslate"><span class="pre">None</span></code>). When doing so, <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-func docutils literal notranslate"><span class="pre">float()</span></code></a> is used to convert the
|
||
integer to a floating-point number before formatting.</p>
|
||
<p>The available presentation types for <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a> and
|
||
<a class="reference internal" href="decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code></a> values are:</p>
|
||
<blockquote>
|
||
<div><table class="docutils align-default">
|
||
<thead>
|
||
<tr class="row-odd"><th class="head"><p>Type</p></th>
|
||
<th class="head"><p>Meaning</p></th>
|
||
</tr>
|
||
</thead>
|
||
<tbody>
|
||
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'e'</span></code></p></td>
|
||
<td><p>Scientific notation. For a given precision <code class="docutils literal notranslate"><span class="pre">p</span></code>,
|
||
formats the number in scientific notation with the
|
||
letter ‘e’ separating the coefficient from the exponent.
|
||
The coefficient has one digit before and <code class="docutils literal notranslate"><span class="pre">p</span></code> digits
|
||
after the decimal point, for a total of <code class="docutils literal notranslate"><span class="pre">p</span> <span class="pre">+</span> <span class="pre">1</span></code>
|
||
significant digits. With no precision given, uses a
|
||
precision of <code class="docutils literal notranslate"><span class="pre">6</span></code> digits after the decimal point for
|
||
<a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a>, and shows all coefficient digits
|
||
for <a class="reference internal" href="decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code></a>. If <code class="docutils literal notranslate"><span class="pre">p=0</span></code>, the decimal
|
||
point is omitted unless the <code class="docutils literal notranslate"><span class="pre">#</span></code> option is used.</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'E'</span></code></p></td>
|
||
<td><p>Scientific notation. Same as <code class="docutils literal notranslate"><span class="pre">'e'</span></code> except it uses
|
||
an upper case ‘E’ as the separator character.</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'f'</span></code></p></td>
|
||
<td><p>Fixed-point notation. For a given precision <code class="docutils literal notranslate"><span class="pre">p</span></code>,
|
||
formats the number as a decimal number with exactly
|
||
<code class="docutils literal notranslate"><span class="pre">p</span></code> digits following the decimal point. With no
|
||
precision given, uses a precision of <code class="docutils literal notranslate"><span class="pre">6</span></code> digits after
|
||
the decimal point for <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a>, and uses a
|
||
precision large enough to show all coefficient digits
|
||
for <a class="reference internal" href="decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code></a>. If <code class="docutils literal notranslate"><span class="pre">p=0</span></code>, the decimal
|
||
point is omitted unless the <code class="docutils literal notranslate"><span class="pre">#</span></code> option is used.</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'F'</span></code></p></td>
|
||
<td><p>Fixed-point notation. Same as <code class="docutils literal notranslate"><span class="pre">'f'</span></code>, but converts
|
||
<code class="docutils literal notranslate"><span class="pre">nan</span></code> to <code class="docutils literal notranslate"><span class="pre">NAN</span></code> and <code class="docutils literal notranslate"><span class="pre">inf</span></code> to <code class="docutils literal notranslate"><span class="pre">INF</span></code>.</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'g'</span></code></p></td>
|
||
<td><p>General format. For a given precision <code class="docutils literal notranslate"><span class="pre">p</span> <span class="pre">>=</span> <span class="pre">1</span></code>,
|
||
this rounds the number to <code class="docutils literal notranslate"><span class="pre">p</span></code> significant digits and
|
||
then formats the result in either fixed-point format
|
||
or in scientific notation, depending on its magnitude.
|
||
A precision of <code class="docutils literal notranslate"><span class="pre">0</span></code> is treated as equivalent to a
|
||
precision of <code class="docutils literal notranslate"><span class="pre">1</span></code>.</p>
|
||
<p>The precise rules are as follows: suppose that the
|
||
result formatted with presentation type <code class="docutils literal notranslate"><span class="pre">'e'</span></code> and
|
||
precision <code class="docutils literal notranslate"><span class="pre">p-1</span></code> would have exponent <code class="docutils literal notranslate"><span class="pre">exp</span></code>. Then,
|
||
if <code class="docutils literal notranslate"><span class="pre">m</span> <span class="pre"><=</span> <span class="pre">exp</span> <span class="pre"><</span> <span class="pre">p</span></code>, where <code class="docutils literal notranslate"><span class="pre">m</span></code> is -4 for floats and -6
|
||
for <a class="reference internal" href="decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">Decimals</span></code></a>, the number is
|
||
formatted with presentation type <code class="docutils literal notranslate"><span class="pre">'f'</span></code> and precision
|
||
<code class="docutils literal notranslate"><span class="pre">p-1-exp</span></code>. Otherwise, the number is formatted
|
||
with presentation type <code class="docutils literal notranslate"><span class="pre">'e'</span></code> and precision <code class="docutils literal notranslate"><span class="pre">p-1</span></code>.
|
||
In both cases insignificant trailing zeros are removed
|
||
from the significand, and the decimal point is also
|
||
removed if there are no remaining digits following it,
|
||
unless the <code class="docutils literal notranslate"><span class="pre">'#'</span></code> option is used.</p>
|
||
<p>With no precision given, uses a precision of <code class="docutils literal notranslate"><span class="pre">6</span></code>
|
||
significant digits for <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a>. For
|
||
<a class="reference internal" href="decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code></a>, the coefficient of the result
|
||
is formed from the coefficient digits of the value;
|
||
scientific notation is used for values smaller than
|
||
<code class="docutils literal notranslate"><span class="pre">1e-6</span></code> in absolute value and values where the place
|
||
value of the least significant digit is larger than 1,
|
||
and fixed-point notation is used otherwise.</p>
|
||
<p>Positive and negative infinity, positive and negative
|
||
zero, and nans, are formatted as <code class="docutils literal notranslate"><span class="pre">inf</span></code>, <code class="docutils literal notranslate"><span class="pre">-inf</span></code>,
|
||
<code class="docutils literal notranslate"><span class="pre">0</span></code>, <code class="docutils literal notranslate"><span class="pre">-0</span></code> and <code class="docutils literal notranslate"><span class="pre">nan</span></code> respectively, regardless of
|
||
the precision.</p>
|
||
</td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'G'</span></code></p></td>
|
||
<td><p>General format. Same as <code class="docutils literal notranslate"><span class="pre">'g'</span></code> except switches to
|
||
<code class="docutils literal notranslate"><span class="pre">'E'</span></code> if the number gets too large. The
|
||
representations of infinity and NaN are uppercased, too.</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'n'</span></code></p></td>
|
||
<td><p>Number. This is the same as <code class="docutils literal notranslate"><span class="pre">'g'</span></code>, except that it uses
|
||
the current locale setting to insert the appropriate
|
||
digit group separators
|
||
for the integral part of a number.</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'%'</span></code></p></td>
|
||
<td><p>Percentage. Multiplies the number by 100 and displays
|
||
in fixed (<code class="docutils literal notranslate"><span class="pre">'f'</span></code>) format, followed by a percent sign.</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p>None</p></td>
|
||
<td><p>For <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a> this is like the <code class="docutils literal notranslate"><span class="pre">'g'</span></code> type, except
|
||
that when fixed-point notation is used to format the
|
||
result, it always includes at least one digit past the
|
||
decimal point, and switches to the scientific notation
|
||
when <code class="docutils literal notranslate"><span class="pre">exp</span> <span class="pre">>=</span> <span class="pre">p</span> <span class="pre">-</span> <span class="pre">1</span></code>. When the precision is not
|
||
specified, the latter will be as large as needed to
|
||
represent the given value faithfully.</p>
|
||
<p>For <a class="reference internal" href="decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code></a>, this is the same as
|
||
either <code class="docutils literal notranslate"><span class="pre">'g'</span></code> or <code class="docutils literal notranslate"><span class="pre">'G'</span></code> depending on the value of
|
||
<code class="docutils literal notranslate"><span class="pre">context.capitals</span></code> for the current decimal context.</p>
|
||
<p>The overall effect is to match the output of <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-func docutils literal notranslate"><span class="pre">str()</span></code></a>
|
||
as altered by the other format modifiers.</p>
|
||
</td>
|
||
</tr>
|
||
</tbody>
|
||
</table>
|
||
</div></blockquote>
|
||
<p>The result should be correctly rounded to a given precision <code class="docutils literal notranslate"><span class="pre">p</span></code> of digits
|
||
after the decimal point. The rounding mode for <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a> matches that
|
||
of the <a class="reference internal" href="functions.html#round" title="round"><code class="xref py py-func docutils literal notranslate"><span class="pre">round()</span></code></a> builtin. For <a class="reference internal" href="decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code></a>, the rounding
|
||
mode of the current <a class="reference internal" href="decimal.html#decimal-context"><span class="std std-ref">context</span></a> will be used.</p>
|
||
<p>The available presentation types for <a class="reference internal" href="functions.html#complex" title="complex"><code class="xref py py-class docutils literal notranslate"><span class="pre">complex</span></code></a> are the same as those for
|
||
<a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a> (<code class="docutils literal notranslate"><span class="pre">'%'</span></code> is not allowed). Both the real and imaginary components
|
||
of a complex number are formatted as floating-point numbers, according to the
|
||
specified presentation type. They are separated by the mandatory sign of the
|
||
imaginary part, the latter being terminated by a <code class="docutils literal notranslate"><span class="pre">j</span></code> suffix. If the presentation
|
||
type is missing, the result will match the output of <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-func docutils literal notranslate"><span class="pre">str()</span></code></a> (complex numbers with
|
||
a non-zero real part are also surrounded by parentheses), possibly altered by
|
||
other format modifiers.</p>
|
||
</section>
|
||
<section id="format-examples">
|
||
<span id="formatexamples"></span><h3>Format examples<a class="headerlink" href="#format-examples" title="Link to this heading">¶</a></h3>
|
||
<p>This section contains examples of the <a class="reference internal" href="stdtypes.html#str.format" title="str.format"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.format()</span></code></a> syntax and
|
||
comparison with the old <code class="docutils literal notranslate"><span class="pre">%</span></code>-formatting.</p>
|
||
<p>In most of the cases the syntax is similar to the old <code class="docutils literal notranslate"><span class="pre">%</span></code>-formatting, with the
|
||
addition of the <code class="docutils literal notranslate"><span class="pre">{}</span></code> and with <code class="docutils literal notranslate"><span class="pre">:</span></code> used instead of <code class="docutils literal notranslate"><span class="pre">%</span></code>.
|
||
For example, <code class="docutils literal notranslate"><span class="pre">'%03.2f'</span></code> can be translated to <code class="docutils literal notranslate"><span class="pre">'{:03.2f}'</span></code>.</p>
|
||
<p>The new format syntax also supports new and different options, shown in the
|
||
following examples.</p>
|
||
<p>Accessing arguments by position:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s1">'</span><span class="si">{0}</span><span class="s1">, </span><span class="si">{1}</span><span class="s1">, </span><span class="si">{2}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="s1">'a'</span><span class="p">,</span> <span class="s1">'b'</span><span class="p">,</span> <span class="s1">'c'</span><span class="p">)</span>
|
||
<span class="go">'a, b, c'</span>
|
||
<span class="gp">>>> </span><span class="s1">'</span><span class="si">{}</span><span class="s1">, </span><span class="si">{}</span><span class="s1">, </span><span class="si">{}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="s1">'a'</span><span class="p">,</span> <span class="s1">'b'</span><span class="p">,</span> <span class="s1">'c'</span><span class="p">)</span> <span class="c1"># 3.1+ only</span>
|
||
<span class="go">'a, b, c'</span>
|
||
<span class="gp">>>> </span><span class="s1">'</span><span class="si">{2}</span><span class="s1">, </span><span class="si">{1}</span><span class="s1">, </span><span class="si">{0}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="s1">'a'</span><span class="p">,</span> <span class="s1">'b'</span><span class="p">,</span> <span class="s1">'c'</span><span class="p">)</span>
|
||
<span class="go">'c, b, a'</span>
|
||
<span class="gp">>>> </span><span class="s1">'</span><span class="si">{2}</span><span class="s1">, </span><span class="si">{1}</span><span class="s1">, </span><span class="si">{0}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="o">*</span><span class="s1">'abc'</span><span class="p">)</span> <span class="c1"># unpacking argument sequence</span>
|
||
<span class="go">'c, b, a'</span>
|
||
<span class="gp">>>> </span><span class="s1">'</span><span class="si">{0}{1}{0}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="s1">'abra'</span><span class="p">,</span> <span class="s1">'cad'</span><span class="p">)</span> <span class="c1"># arguments' indices can be repeated</span>
|
||
<span class="go">'abracadabra'</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>Accessing arguments by name:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s1">'Coordinates: </span><span class="si">{latitude}</span><span class="s1">, </span><span class="si">{longitude}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">latitude</span><span class="o">=</span><span class="s1">'37.24N'</span><span class="p">,</span> <span class="n">longitude</span><span class="o">=</span><span class="s1">'-115.81W'</span><span class="p">)</span>
|
||
<span class="go">'Coordinates: 37.24N, -115.81W'</span>
|
||
<span class="gp">>>> </span><span class="n">coord</span> <span class="o">=</span> <span class="p">{</span><span class="s1">'latitude'</span><span class="p">:</span> <span class="s1">'37.24N'</span><span class="p">,</span> <span class="s1">'longitude'</span><span class="p">:</span> <span class="s1">'-115.81W'</span><span class="p">}</span>
|
||
<span class="gp">>>> </span><span class="s1">'Coordinates: </span><span class="si">{latitude}</span><span class="s1">, </span><span class="si">{longitude}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="o">**</span><span class="n">coord</span><span class="p">)</span>
|
||
<span class="go">'Coordinates: 37.24N, -115.81W'</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>Accessing arguments’ attributes:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">c</span> <span class="o">=</span> <span class="mi">3</span><span class="o">-</span><span class="mi">5</span><span class="n">j</span>
|
||
<span class="gp">>>> </span><span class="p">(</span><span class="s1">'The complex number </span><span class="si">{0}</span><span class="s1"> is formed from the real part </span><span class="si">{0.real}</span><span class="s1"> '</span>
|
||
<span class="gp">... </span> <span class="s1">'and the imaginary part </span><span class="si">{0.imag}</span><span class="s1">.'</span><span class="p">)</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">c</span><span class="p">)</span>
|
||
<span class="go">'The complex number (3-5j) is formed from the real part 3.0 and the imaginary part -5.0.'</span>
|
||
<span class="gp">>>> </span><span class="k">class</span><span class="w"> </span><span class="nc">Point</span><span class="p">:</span>
|
||
<span class="gp">... </span> <span class="k">def</span><span class="w"> </span><span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">):</span>
|
||
<span class="gp">... </span> <span class="bp">self</span><span class="o">.</span><span class="n">x</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">y</span> <span class="o">=</span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span>
|
||
<span class="gp">... </span> <span class="k">def</span><span class="w"> </span><span class="fm">__str__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
|
||
<span class="gp">... </span> <span class="k">return</span> <span class="s1">'Point(</span><span class="si">{self.x}</span><span class="s1">, </span><span class="si">{self.y}</span><span class="s1">)'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="bp">self</span><span class="o">=</span><span class="bp">self</span><span class="p">)</span>
|
||
<span class="gp">...</span>
|
||
<span class="gp">>>> </span><span class="nb">str</span><span class="p">(</span><span class="n">Point</span><span class="p">(</span><span class="mi">4</span><span class="p">,</span> <span class="mi">2</span><span class="p">))</span>
|
||
<span class="go">'Point(4, 2)'</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>Accessing arguments’ items:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">coord</span> <span class="o">=</span> <span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="mi">5</span><span class="p">)</span>
|
||
<span class="gp">>>> </span><span class="s1">'X: </span><span class="si">{0[0]}</span><span class="s1">; Y: </span><span class="si">{0[1]}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">coord</span><span class="p">)</span>
|
||
<span class="go">'X: 3; Y: 5'</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>Replacing <code class="docutils literal notranslate"><span class="pre">%s</span></code> and <code class="docutils literal notranslate"><span class="pre">%r</span></code>:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s2">"repr() shows quotes: </span><span class="si">{!r}</span><span class="s2">; str() doesn't: </span><span class="si">{!s}</span><span class="s2">"</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="s1">'test1'</span><span class="p">,</span> <span class="s1">'test2'</span><span class="p">)</span>
|
||
<span class="go">"repr() shows quotes: 'test1'; str() doesn't: test2"</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>Aligning the text and specifying a width:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s1">'</span><span class="si">{:<30}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="s1">'left aligned'</span><span class="p">)</span>
|
||
<span class="go">'left aligned '</span>
|
||
<span class="gp">>>> </span><span class="s1">'</span><span class="si">{:>30}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="s1">'right aligned'</span><span class="p">)</span>
|
||
<span class="go">' right aligned'</span>
|
||
<span class="gp">>>> </span><span class="s1">'</span><span class="si">{:^30}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="s1">'centered'</span><span class="p">)</span>
|
||
<span class="go">' centered '</span>
|
||
<span class="gp">>>> </span><span class="s1">'</span><span class="si">{:*^30}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="s1">'centered'</span><span class="p">)</span> <span class="c1"># use '*' as a fill char</span>
|
||
<span class="go">'***********centered***********'</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>Replacing <code class="docutils literal notranslate"><span class="pre">%+f</span></code>, <code class="docutils literal notranslate"><span class="pre">%-f</span></code>, and <code class="docutils literal notranslate"><span class="pre">%</span> <span class="pre">f</span></code> and specifying a sign:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s1">'</span><span class="si">{:+f}</span><span class="s1">; </span><span class="si">{:+f}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="mf">3.14</span><span class="p">,</span> <span class="o">-</span><span class="mf">3.14</span><span class="p">)</span> <span class="c1"># show it always</span>
|
||
<span class="go">'+3.140000; -3.140000'</span>
|
||
<span class="gp">>>> </span><span class="s1">'</span><span class="si">{: f}</span><span class="s1">; </span><span class="si">{: f}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="mf">3.14</span><span class="p">,</span> <span class="o">-</span><span class="mf">3.14</span><span class="p">)</span> <span class="c1"># show a space for positive numbers</span>
|
||
<span class="go">' 3.140000; -3.140000'</span>
|
||
<span class="gp">>>> </span><span class="s1">'</span><span class="si">{:-f}</span><span class="s1">; </span><span class="si">{:-f}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="mf">3.14</span><span class="p">,</span> <span class="o">-</span><span class="mf">3.14</span><span class="p">)</span> <span class="c1"># show only the minus -- same as '{:f}; {:f}'</span>
|
||
<span class="go">'3.140000; -3.140000'</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>Replacing <code class="docutils literal notranslate"><span class="pre">%x</span></code> and <code class="docutils literal notranslate"><span class="pre">%o</span></code> and converting the value to different bases:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="c1"># format also supports binary numbers</span>
|
||
<span class="gp">>>> </span><span class="s2">"int: </span><span class="si">{0:d}</span><span class="s2">; hex: </span><span class="si">{0:x}</span><span class="s2">; oct: </span><span class="si">{0:o}</span><span class="s2">; bin: </span><span class="si">{0:b}</span><span class="s2">"</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="mi">42</span><span class="p">)</span>
|
||
<span class="go">'int: 42; hex: 2a; oct: 52; bin: 101010'</span>
|
||
<span class="gp">>>> </span><span class="c1"># with 0x, 0o, or 0b as prefix:</span>
|
||
<span class="gp">>>> </span><span class="s2">"int: </span><span class="si">{0:d}</span><span class="s2">; hex: </span><span class="si">{0:#x}</span><span class="s2">; oct: </span><span class="si">{0:#o}</span><span class="s2">; bin: </span><span class="si">{0:#b}</span><span class="s2">"</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="mi">42</span><span class="p">)</span>
|
||
<span class="go">'int: 42; hex: 0x2a; oct: 0o52; bin: 0b101010'</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>Using the comma or the underscore as a digit group separator:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s1">'</span><span class="si">{:,}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="mi">1234567890</span><span class="p">)</span>
|
||
<span class="go">'1,234,567,890'</span>
|
||
<span class="gp">>>> </span><span class="s1">'{:_}'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="mi">1234567890</span><span class="p">)</span>
|
||
<span class="go">'1_234_567_890'</span>
|
||
<span class="gp">>>> </span><span class="s1">'{:_b}'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="mi">1234567890</span><span class="p">)</span>
|
||
<span class="go">'100_1001_1001_0110_0000_0010_1101_0010'</span>
|
||
<span class="gp">>>> </span><span class="s1">'{:_x}'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="mi">1234567890</span><span class="p">)</span>
|
||
<span class="go">'4996_02d2'</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>Expressing a percentage:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">points</span> <span class="o">=</span> <span class="mi">19</span>
|
||
<span class="gp">>>> </span><span class="n">total</span> <span class="o">=</span> <span class="mi">22</span>
|
||
<span class="gp">>>> </span><span class="s1">'Correct answers: </span><span class="si">{:.2%}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">points</span><span class="o">/</span><span class="n">total</span><span class="p">)</span>
|
||
<span class="go">'Correct answers: 86.36%'</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>Using type-specific formatting:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span><span class="w"> </span><span class="nn">datetime</span>
|
||
<span class="gp">>>> </span><span class="n">d</span> <span class="o">=</span> <span class="n">datetime</span><span class="o">.</span><span class="n">datetime</span><span class="p">(</span><span class="mi">2010</span><span class="p">,</span> <span class="mi">7</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="mi">12</span><span class="p">,</span> <span class="mi">15</span><span class="p">,</span> <span class="mi">58</span><span class="p">)</span>
|
||
<span class="gp">>>> </span><span class="s1">'{:%Y-%m-</span><span class="si">%d</span><span class="s1"> %H:%M:%S}'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">d</span><span class="p">)</span>
|
||
<span class="go">'2010-07-04 12:15:58'</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>Nesting arguments and more complex examples:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="k">for</span> <span class="n">align</span><span class="p">,</span> <span class="n">text</span> <span class="ow">in</span> <span class="nb">zip</span><span class="p">(</span><span class="s1">'<^>'</span><span class="p">,</span> <span class="p">[</span><span class="s1">'left'</span><span class="p">,</span> <span class="s1">'center'</span><span class="p">,</span> <span class="s1">'right'</span><span class="p">]):</span>
|
||
<span class="gp">... </span> <span class="s1">'{0:</span><span class="si">{fill}{align}</span><span class="s1">16}'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">text</span><span class="p">,</span> <span class="n">fill</span><span class="o">=</span><span class="n">align</span><span class="p">,</span> <span class="n">align</span><span class="o">=</span><span class="n">align</span><span class="p">)</span>
|
||
<span class="gp">...</span>
|
||
<span class="go">'left<<<<<<<<<<<<'</span>
|
||
<span class="go">'^^^^^center^^^^^'</span>
|
||
<span class="go">'>>>>>>>>>>>right'</span>
|
||
<span class="gp">>>></span>
|
||
<span class="gp">>>> </span><span class="n">octets</span> <span class="o">=</span> <span class="p">[</span><span class="mi">192</span><span class="p">,</span> <span class="mi">168</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">1</span><span class="p">]</span>
|
||
<span class="gp">>>> </span><span class="s1">'</span><span class="si">{:02X}{:02X}{:02X}{:02X}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="o">*</span><span class="n">octets</span><span class="p">)</span>
|
||
<span class="go">'C0A80001'</span>
|
||
<span class="gp">>>> </span><span class="nb">int</span><span class="p">(</span><span class="n">_</span><span class="p">,</span> <span class="mi">16</span><span class="p">)</span>
|
||
<span class="go">3232235521</span>
|
||
<span class="gp">>>></span>
|
||
<span class="gp">>>> </span><span class="n">width</span> <span class="o">=</span> <span class="mi">5</span>
|
||
<span class="gp">>>> </span><span class="k">for</span> <span class="n">num</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span><span class="mi">12</span><span class="p">):</span>
|
||
<span class="gp">... </span> <span class="k">for</span> <span class="n">base</span> <span class="ow">in</span> <span class="s1">'dXob'</span><span class="p">:</span>
|
||
<span class="gp">... </span> <span class="nb">print</span><span class="p">(</span><span class="s1">'{0:</span><span class="si">{width}{base}</span><span class="s1">}'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">num</span><span class="p">,</span> <span class="n">base</span><span class="o">=</span><span class="n">base</span><span class="p">,</span> <span class="n">width</span><span class="o">=</span><span class="n">width</span><span class="p">),</span> <span class="n">end</span><span class="o">=</span><span class="s1">' '</span><span class="p">)</span>
|
||
<span class="gp">... </span> <span class="nb">print</span><span class="p">()</span>
|
||
<span class="gp">...</span>
|
||
<span class="go"> 5 5 5 101</span>
|
||
<span class="go"> 6 6 6 110</span>
|
||
<span class="go"> 7 7 7 111</span>
|
||
<span class="go"> 8 8 10 1000</span>
|
||
<span class="go"> 9 9 11 1001</span>
|
||
<span class="go"> 10 A 12 1010</span>
|
||
<span class="go"> 11 B 13 1011</span>
|
||
</pre></div>
|
||
</div>
|
||
</section>
|
||
</section>
|
||
<section id="template-strings">
|
||
<span id="id1"></span><h2>Template strings<a class="headerlink" href="#template-strings" title="Link to this heading">¶</a></h2>
|
||
<p>Template strings provide simpler string substitutions as described in
|
||
<span class="target" id="index-11"></span><a class="pep reference external" href="https://peps.python.org/pep-0292/"><strong>PEP 292</strong></a>. A primary use case for template strings is for
|
||
internationalization (i18n) since in that context, the simpler syntax and
|
||
functionality makes it easier to translate than other built-in string
|
||
formatting facilities in Python. As an example of a library built on template
|
||
strings for i18n, see the
|
||
<a class="reference external" href="https://flufli18n.readthedocs.io/en/latest/">flufl.i18n</a> package.</p>
|
||
<p id="index-12">Template strings support <code class="docutils literal notranslate"><span class="pre">$</span></code>-based substitutions, using the following rules:</p>
|
||
<ul class="simple">
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">$$</span></code> is an escape; it is replaced with a single <code class="docutils literal notranslate"><span class="pre">$</span></code>.</p></li>
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">$identifier</span></code> names a substitution placeholder matching a mapping key of
|
||
<code class="docutils literal notranslate"><span class="pre">"identifier"</span></code>. By default, <code class="docutils literal notranslate"><span class="pre">"identifier"</span></code> is restricted to any
|
||
case-insensitive ASCII alphanumeric string (including underscores) that
|
||
starts with an underscore or ASCII letter. The first non-identifier
|
||
character after the <code class="docutils literal notranslate"><span class="pre">$</span></code> character terminates this placeholder
|
||
specification.</p></li>
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">${identifier}</span></code> is equivalent to <code class="docutils literal notranslate"><span class="pre">$identifier</span></code>. It is required when
|
||
valid identifier characters follow the placeholder but are not part of the
|
||
placeholder, such as <code class="docutils literal notranslate"><span class="pre">"${noun}ification"</span></code>.</p></li>
|
||
</ul>
|
||
<p>Any other appearance of <code class="docutils literal notranslate"><span class="pre">$</span></code> in the string will result in a <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a>
|
||
being raised.</p>
|
||
<p>The <a class="reference internal" href="#module-string" title="string: Common string operations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">string</span></code></a> module provides a <a class="reference internal" href="#string.Template" title="string.Template"><code class="xref py py-class docutils literal notranslate"><span class="pre">Template</span></code></a> class that implements
|
||
these rules. The methods of <a class="reference internal" href="#string.Template" title="string.Template"><code class="xref py py-class docutils literal notranslate"><span class="pre">Template</span></code></a> are:</p>
|
||
<dl class="py class">
|
||
<dt class="sig sig-object py" id="string.Template">
|
||
<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">string.</span></span><span class="sig-name descname"><span class="pre">Template</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">template</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#string.Template" title="Link to this definition">¶</a></dt>
|
||
<dd><p>The constructor takes a single argument which is the template string.</p>
|
||
<dl class="py method">
|
||
<dt class="sig sig-object py" id="string.Template.substitute">
|
||
<span class="sig-name descname"><span class="pre">substitute</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">mapping</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">{}</span></span></em>, <em class="sig-param"><span class="positional-only-separator o"><abbr title="Positional-only parameter separator (PEP 570)"><span class="pre">/</span></abbr></span></em>, <em class="sig-param"><span class="o"><span class="pre">**</span></span><span class="n"><span class="pre">kwds</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#string.Template.substitute" title="Link to this definition">¶</a></dt>
|
||
<dd><p>Performs the template substitution, returning a new string. <em>mapping</em> is
|
||
any dictionary-like object with keys that match the placeholders in the
|
||
template. Alternatively, you can provide keyword arguments, where the
|
||
keywords are the placeholders. When both <em>mapping</em> and <em>kwds</em> are given
|
||
and there are duplicates, the placeholders from <em>kwds</em> take precedence.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="py method">
|
||
<dt class="sig sig-object py" id="string.Template.safe_substitute">
|
||
<span class="sig-name descname"><span class="pre">safe_substitute</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">mapping</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">{}</span></span></em>, <em class="sig-param"><span class="positional-only-separator o"><abbr title="Positional-only parameter separator (PEP 570)"><span class="pre">/</span></abbr></span></em>, <em class="sig-param"><span class="o"><span class="pre">**</span></span><span class="n"><span class="pre">kwds</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#string.Template.safe_substitute" title="Link to this definition">¶</a></dt>
|
||
<dd><p>Like <a class="reference internal" href="#string.Template.substitute" title="string.Template.substitute"><code class="xref py py-meth docutils literal notranslate"><span class="pre">substitute()</span></code></a>, except that if placeholders are missing from
|
||
<em>mapping</em> and <em>kwds</em>, instead of raising a <a class="reference internal" href="exceptions.html#KeyError" title="KeyError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">KeyError</span></code></a> exception, the
|
||
original placeholder will appear in the resulting string intact. Also,
|
||
unlike with <a class="reference internal" href="#string.Template.substitute" title="string.Template.substitute"><code class="xref py py-meth docutils literal notranslate"><span class="pre">substitute()</span></code></a>, any other appearances of the <code class="docutils literal notranslate"><span class="pre">$</span></code> will
|
||
simply return <code class="docutils literal notranslate"><span class="pre">$</span></code> instead of raising <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a>.</p>
|
||
<p>While other exceptions may still occur, this method is called “safe”
|
||
because it always tries to return a usable string instead of
|
||
raising an exception. In another sense, <a class="reference internal" href="#string.Template.safe_substitute" title="string.Template.safe_substitute"><code class="xref py py-meth docutils literal notranslate"><span class="pre">safe_substitute()</span></code></a> may be
|
||
anything other than safe, since it will silently ignore malformed
|
||
templates containing dangling delimiters, unmatched braces, or
|
||
placeholders that are not valid Python identifiers.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="py method">
|
||
<dt class="sig sig-object py" id="string.Template.is_valid">
|
||
<span class="sig-name descname"><span class="pre">is_valid</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#string.Template.is_valid" title="Link to this definition">¶</a></dt>
|
||
<dd><p>Returns false if the template has invalid placeholders that will cause
|
||
<a class="reference internal" href="#string.Template.substitute" title="string.Template.substitute"><code class="xref py py-meth docutils literal notranslate"><span class="pre">substitute()</span></code></a> to raise <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a>.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">Added in version 3.11.</span></p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="py method">
|
||
<dt class="sig sig-object py" id="string.Template.get_identifiers">
|
||
<span class="sig-name descname"><span class="pre">get_identifiers</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#string.Template.get_identifiers" title="Link to this definition">¶</a></dt>
|
||
<dd><p>Returns a list of the valid identifiers in the template, in the order
|
||
they first appear, ignoring any invalid identifiers.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">Added in version 3.11.</span></p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<p><a class="reference internal" href="#string.Template" title="string.Template"><code class="xref py py-class docutils literal notranslate"><span class="pre">Template</span></code></a> instances also provide one public data attribute:</p>
|
||
<dl class="py attribute">
|
||
<dt class="sig sig-object py" id="string.Template.template">
|
||
<span class="sig-name descname"><span class="pre">template</span></span><a class="headerlink" href="#string.Template.template" title="Link to this definition">¶</a></dt>
|
||
<dd><p>This is the object passed to the constructor’s <em>template</em> argument. In
|
||
general, you shouldn’t change it, but read-only access is not enforced.</p>
|
||
</dd></dl>
|
||
|
||
</dd></dl>
|
||
|
||
<p>Here is an example of how to use a Template:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">from</span><span class="w"> </span><span class="nn">string</span><span class="w"> </span><span class="kn">import</span> <span class="n">Template</span>
|
||
<span class="gp">>>> </span><span class="n">s</span> <span class="o">=</span> <span class="n">Template</span><span class="p">(</span><span class="s1">'$who likes $what'</span><span class="p">)</span>
|
||
<span class="gp">>>> </span><span class="n">s</span><span class="o">.</span><span class="n">substitute</span><span class="p">(</span><span class="n">who</span><span class="o">=</span><span class="s1">'tim'</span><span class="p">,</span> <span class="n">what</span><span class="o">=</span><span class="s1">'kung pao'</span><span class="p">)</span>
|
||
<span class="go">'tim likes kung pao'</span>
|
||
<span class="gp">>>> </span><span class="n">d</span> <span class="o">=</span> <span class="nb">dict</span><span class="p">(</span><span class="n">who</span><span class="o">=</span><span class="s1">'tim'</span><span class="p">)</span>
|
||
<span class="gp">>>> </span><span class="n">Template</span><span class="p">(</span><span class="s1">'Give $who $100'</span><span class="p">)</span><span class="o">.</span><span class="n">substitute</span><span class="p">(</span><span class="n">d</span><span class="p">)</span>
|
||
<span class="gt">Traceback (most recent call last):</span>
|
||
<span class="c">...</span>
|
||
<span class="gr">ValueError</span>: <span class="n">Invalid placeholder in string: line 1, col 11</span>
|
||
<span class="gp">>>> </span><span class="n">Template</span><span class="p">(</span><span class="s1">'$who likes $what'</span><span class="p">)</span><span class="o">.</span><span class="n">substitute</span><span class="p">(</span><span class="n">d</span><span class="p">)</span>
|
||
<span class="gt">Traceback (most recent call last):</span>
|
||
<span class="c">...</span>
|
||
<span class="gr">KeyError</span>: <span class="n">'what'</span>
|
||
<span class="gp">>>> </span><span class="n">Template</span><span class="p">(</span><span class="s1">'$who likes $what'</span><span class="p">)</span><span class="o">.</span><span class="n">safe_substitute</span><span class="p">(</span><span class="n">d</span><span class="p">)</span>
|
||
<span class="go">'tim likes $what'</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>Advanced usage: you can derive subclasses of <a class="reference internal" href="#string.Template" title="string.Template"><code class="xref py py-class docutils literal notranslate"><span class="pre">Template</span></code></a> to customize
|
||
the placeholder syntax, delimiter character, or the entire regular expression
|
||
used to parse template strings. To do this, you can override these class
|
||
attributes:</p>
|
||
<ul>
|
||
<li><p><em>delimiter</em> – This is the literal string describing a placeholder
|
||
introducing delimiter. The default value is <code class="docutils literal notranslate"><span class="pre">$</span></code>. Note that this should
|
||
<em>not</em> be a regular expression, as the implementation will call
|
||
<a class="reference internal" href="re.html#re.escape" title="re.escape"><code class="xref py py-meth docutils literal notranslate"><span class="pre">re.escape()</span></code></a> on this string as needed. Note further that you cannot
|
||
change the delimiter after class creation (i.e. a different delimiter must
|
||
be set in the subclass’s class namespace).</p></li>
|
||
<li><p><em>idpattern</em> – This is the regular expression describing the pattern for
|
||
non-braced placeholders. The default value is the regular expression
|
||
<code class="docutils literal notranslate"><span class="pre">(?a:[_a-z][_a-z0-9]*)</span></code>. If this is given and <em>braceidpattern</em> is
|
||
<code class="docutils literal notranslate"><span class="pre">None</span></code> this pattern will also apply to braced placeholders.</p>
|
||
<div class="admonition note">
|
||
<p class="admonition-title">Note</p>
|
||
<p>Since default <em>flags</em> is <code class="docutils literal notranslate"><span class="pre">re.IGNORECASE</span></code>, pattern <code class="docutils literal notranslate"><span class="pre">[a-z]</span></code> can match
|
||
with some non-ASCII characters. That’s why we use the local <code class="docutils literal notranslate"><span class="pre">a</span></code> flag
|
||
here.</p>
|
||
</div>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.7: </span><em>braceidpattern</em> can be used to define separate patterns used inside and
|
||
outside the braces.</p>
|
||
</div>
|
||
</li>
|
||
<li><p><em>braceidpattern</em> – This is like <em>idpattern</em> but describes the pattern for
|
||
braced placeholders. Defaults to <code class="docutils literal notranslate"><span class="pre">None</span></code> which means to fall back to
|
||
<em>idpattern</em> (i.e. the same pattern is used both inside and outside braces).
|
||
If given, this allows you to define different patterns for braced and
|
||
unbraced placeholders.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">Added in version 3.7.</span></p>
|
||
</div>
|
||
</li>
|
||
<li><p><em>flags</em> – The regular expression flags that will be applied when compiling
|
||
the regular expression used for recognizing substitutions. The default value
|
||
is <code class="docutils literal notranslate"><span class="pre">re.IGNORECASE</span></code>. Note that <code class="docutils literal notranslate"><span class="pre">re.VERBOSE</span></code> will always be added to the
|
||
flags, so custom <em>idpattern</em>s must follow conventions for verbose regular
|
||
expressions.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">Added in version 3.2.</span></p>
|
||
</div>
|
||
</li>
|
||
</ul>
|
||
<p>Alternatively, you can provide the entire regular expression pattern by
|
||
overriding the class attribute <em>pattern</em>. If you do this, the value must be a
|
||
regular expression object with four named capturing groups. The capturing
|
||
groups correspond to the rules given above, along with the invalid placeholder
|
||
rule:</p>
|
||
<ul class="simple">
|
||
<li><p><em>escaped</em> – This group matches the escape sequence, e.g. <code class="docutils literal notranslate"><span class="pre">$$</span></code>, in the
|
||
default pattern.</p></li>
|
||
<li><p><em>named</em> – This group matches the unbraced placeholder name; it should not
|
||
include the delimiter in capturing group.</p></li>
|
||
<li><p><em>braced</em> – This group matches the brace enclosed placeholder name; it should
|
||
not include either the delimiter or braces in the capturing group.</p></li>
|
||
<li><p><em>invalid</em> – This group matches any other delimiter pattern (usually a single
|
||
delimiter), and it should appear last in the regular expression.</p></li>
|
||
</ul>
|
||
<p>The methods on this class will raise <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> if the pattern matches
|
||
the template without one of these named groups matching.</p>
|
||
</section>
|
||
<section id="helper-functions">
|
||
<h2>Helper functions<a class="headerlink" href="#helper-functions" title="Link to this heading">¶</a></h2>
|
||
<dl class="py function">
|
||
<dt class="sig sig-object py" id="string.capwords">
|
||
<span class="sig-prename descclassname"><span class="pre">string.</span></span><span class="sig-name descname"><span class="pre">capwords</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">s</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">sep</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#string.capwords" title="Link to this definition">¶</a></dt>
|
||
<dd><p>Split the argument into words using <a class="reference internal" href="stdtypes.html#str.split" title="str.split"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.split()</span></code></a>, capitalize each word
|
||
using <a class="reference internal" href="stdtypes.html#str.capitalize" title="str.capitalize"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.capitalize()</span></code></a>, and join the capitalized words using
|
||
<a class="reference internal" href="stdtypes.html#str.join" title="str.join"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.join()</span></code></a>. If the optional second argument <em>sep</em> is absent
|
||
or <code class="docutils literal notranslate"><span class="pre">None</span></code>, runs of whitespace characters are replaced by a single space
|
||
and leading and trailing whitespace are removed, otherwise <em>sep</em> is used to
|
||
split and join the words.</p>
|
||
</dd></dl>
|
||
|
||
</section>
|
||
</section>
|
||
|
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|
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<ul>
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<li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">string</span></code> — Common string operations</a><ul>
|
||
<li><a class="reference internal" href="#string-constants">String constants</a></li>
|
||
<li><a class="reference internal" href="#custom-string-formatting">Custom String Formatting</a></li>
|
||
<li><a class="reference internal" href="#format-string-syntax">Format String Syntax</a><ul>
|
||
<li><a class="reference internal" href="#format-specification-mini-language">Format Specification Mini-Language</a></li>
|
||
<li><a class="reference internal" href="#format-examples">Format examples</a></li>
|
||
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|
||
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|
||
<li><a class="reference internal" href="#template-strings">Template strings</a></li>
|
||
<li><a class="reference internal" href="#helper-functions">Helper functions</a></li>
|
||
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|
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