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<section id="what-s-new-in-python-3-1">
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<h1>What’s New In Python 3.1<a class="headerlink" href="#what-s-new-in-python-3-1" title="Link to this heading">¶</a></h1>
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<dl class="field-list simple">
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<dt class="field-odd">Author<span class="colon">:</span></dt>
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<dd class="field-odd"><p>Raymond Hettinger</p>
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</dd>
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</dl>
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<p>This article explains the new features in Python 3.1, compared to 3.0.
|
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Python 3.1 was released on June 27, 2009.</p>
|
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<section id="pep-372-ordered-dictionaries">
|
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<h2>PEP 372: Ordered Dictionaries<a class="headerlink" href="#pep-372-ordered-dictionaries" title="Link to this heading">¶</a></h2>
|
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<p>Regular Python dictionaries iterate over key/value pairs in arbitrary order.
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Over the years, a number of authors have written alternative implementations
|
||
that remember the order that the keys were originally inserted. Based on
|
||
the experiences from those implementations, a new
|
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<a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">collections.OrderedDict</span></code></a> class has been introduced.</p>
|
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<p>The OrderedDict API is substantially the same as regular dictionaries
|
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but will iterate over keys and values in a guaranteed order depending on
|
||
when a key was first inserted. If a new entry overwrites an existing entry,
|
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the original insertion position is left unchanged. Deleting an entry and
|
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reinserting it will move it to the end.</p>
|
||
<p>The standard library now supports use of ordered dictionaries in several
|
||
modules. The <a class="reference internal" href="../library/configparser.html#module-configparser" title="configparser: Configuration file parser."><code class="xref py py-mod docutils literal notranslate"><span class="pre">configparser</span></code></a> module uses them by default. This lets
|
||
configuration files be read, modified, and then written back in their original
|
||
order. The <em>_asdict()</em> method for <a class="reference internal" href="../library/collections.html#collections.namedtuple" title="collections.namedtuple"><code class="xref py py-func docutils literal notranslate"><span class="pre">collections.namedtuple()</span></code></a> now
|
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returns an ordered dictionary with the values appearing in the same order as
|
||
the underlying tuple indices. The <a class="reference internal" href="../library/json.html#module-json" title="json: Encode and decode the JSON format."><code class="xref py py-mod docutils literal notranslate"><span class="pre">json</span></code></a> module is being built-out with
|
||
an <em>object_pairs_hook</em> to allow OrderedDicts to be built by the decoder.
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Support was also added for third-party tools like <a class="reference external" href="https://pyyaml.org/">PyYAML</a>.</p>
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||
<div class="admonition seealso">
|
||
<p class="admonition-title">See also</p>
|
||
<dl class="simple">
|
||
<dt><span class="target" id="index-0"></span><a class="pep reference external" href="https://peps.python.org/pep-0372/"><strong>PEP 372</strong></a> - Ordered Dictionaries</dt><dd><p>PEP written by Armin Ronacher and Raymond Hettinger. Implementation
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written by Raymond Hettinger.</p>
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</dd>
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</dl>
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</div>
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<p>Since an ordered dictionary remembers its insertion order, it can be used
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in conjunction with sorting to make a sorted dictionary:</p>
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<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="c1"># regular unsorted dictionary</span>
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<span class="gp">>>> </span><span class="n">d</span> <span class="o">=</span> <span class="p">{</span><span class="s1">'banana'</span><span class="p">:</span> <span class="mi">3</span><span class="p">,</span> <span class="s1">'apple'</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span> <span class="s1">'pear'</span><span class="p">:</span> <span class="mi">1</span><span class="p">,</span> <span class="s1">'orange'</span><span class="p">:</span> <span class="mi">2</span><span class="p">}</span>
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<span class="gp">>>> </span><span class="c1"># dictionary sorted by key</span>
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<span class="gp">>>> </span><span class="n">OrderedDict</span><span class="p">(</span><span class="nb">sorted</span><span class="p">(</span><span class="n">d</span><span class="o">.</span><span class="n">items</span><span class="p">(),</span> <span class="n">key</span><span class="o">=</span><span class="k">lambda</span> <span class="n">t</span><span class="p">:</span> <span class="n">t</span><span class="p">[</span><span class="mi">0</span><span class="p">]))</span>
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<span class="go">OrderedDict([('apple', 4), ('banana', 3), ('orange', 2), ('pear', 1)])</span>
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<span class="gp">>>> </span><span class="c1"># dictionary sorted by value</span>
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<span class="gp">>>> </span><span class="n">OrderedDict</span><span class="p">(</span><span class="nb">sorted</span><span class="p">(</span><span class="n">d</span><span class="o">.</span><span class="n">items</span><span class="p">(),</span> <span class="n">key</span><span class="o">=</span><span class="k">lambda</span> <span class="n">t</span><span class="p">:</span> <span class="n">t</span><span class="p">[</span><span class="mi">1</span><span class="p">]))</span>
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<span class="go">OrderedDict([('pear', 1), ('orange', 2), ('banana', 3), ('apple', 4)])</span>
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<span class="gp">>>> </span><span class="c1"># dictionary sorted by length of the key string</span>
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<span class="gp">>>> </span><span class="n">OrderedDict</span><span class="p">(</span><span class="nb">sorted</span><span class="p">(</span><span class="n">d</span><span class="o">.</span><span class="n">items</span><span class="p">(),</span> <span class="n">key</span><span class="o">=</span><span class="k">lambda</span> <span class="n">t</span><span class="p">:</span> <span class="nb">len</span><span class="p">(</span><span class="n">t</span><span class="p">[</span><span class="mi">0</span><span class="p">])))</span>
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<span class="go">OrderedDict([('pear', 1), ('apple', 4), ('orange', 2), ('banana', 3)])</span>
|
||
</pre></div>
|
||
</div>
|
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<p>The new sorted dictionaries maintain their sort order when entries
|
||
are deleted. But when new keys are added, the keys are appended
|
||
to the end and the sort is not maintained.</p>
|
||
</section>
|
||
<section id="pep-378-format-specifier-for-thousands-separator">
|
||
<h2>PEP 378: Format Specifier for Thousands Separator<a class="headerlink" href="#pep-378-format-specifier-for-thousands-separator" title="Link to this heading">¶</a></h2>
|
||
<p>The built-in <a class="reference internal" href="../library/functions.html#format" title="format"><code class="xref py py-func docutils literal notranslate"><span class="pre">format()</span></code></a> function and the <a class="reference internal" href="../library/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 use
|
||
a mini-language that now includes a simple, non-locale aware way to format
|
||
a number with a thousands separator. That provides a way to humanize a
|
||
program’s output, improving its professional appearance and readability:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="nb">format</span><span class="p">(</span><span class="mi">1234567</span><span class="p">,</span> <span class="s1">',d'</span><span class="p">)</span>
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||
<span class="go">'1,234,567'</span>
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<span class="gp">>>> </span><span class="nb">format</span><span class="p">(</span><span class="mf">1234567.89</span><span class="p">,</span> <span class="s1">',.2f'</span><span class="p">)</span>
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||
<span class="go">'1,234,567.89'</span>
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||
<span class="gp">>>> </span><span class="nb">format</span><span class="p">(</span><span class="mf">12345.6</span> <span class="o">+</span> <span class="mf">8901234.12</span><span class="n">j</span><span class="p">,</span> <span class="s1">',f'</span><span class="p">)</span>
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||
<span class="go">'12,345.600000+8,901,234.120000j'</span>
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<span class="gp">>>> </span><span class="nb">format</span><span class="p">(</span><span class="n">Decimal</span><span class="p">(</span><span class="s1">'1234567.89'</span><span class="p">),</span> <span class="s1">',f'</span><span class="p">)</span>
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||
<span class="go">'1,234,567.89'</span>
|
||
</pre></div>
|
||
</div>
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||
<p>The supported types are <a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate"><span class="pre">int</span></code></a>, <a class="reference internal" href="../library/functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a>, <a class="reference internal" href="../library/functions.html#complex" title="complex"><code class="xref py py-class docutils literal notranslate"><span class="pre">complex</span></code></a>
|
||
and <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">decimal.Decimal</span></code></a>.</p>
|
||
<p>Discussions are underway about how to specify alternative separators
|
||
like dots, spaces, apostrophes, or underscores. Locale-aware applications
|
||
should use the existing <em>n</em> format specifier which already has some support
|
||
for thousands separators.</p>
|
||
<div class="admonition seealso">
|
||
<p class="admonition-title">See also</p>
|
||
<dl class="simple">
|
||
<dt><span class="target" id="index-1"></span><a class="pep reference external" href="https://peps.python.org/pep-0378/"><strong>PEP 378</strong></a> - Format Specifier for Thousands Separator</dt><dd><p>PEP written by Raymond Hettinger and implemented by Eric Smith and
|
||
Mark Dickinson.</p>
|
||
</dd>
|
||
</dl>
|
||
</div>
|
||
</section>
|
||
<section id="other-language-changes">
|
||
<h2>Other Language Changes<a class="headerlink" href="#other-language-changes" title="Link to this heading">¶</a></h2>
|
||
<p>Some smaller changes made to the core Python language are:</p>
|
||
<ul>
|
||
<li><p>Directories and zip archives containing a <code class="file docutils literal notranslate"><span class="pre">__main__.py</span></code>
|
||
file can now be executed directly by passing their name to the
|
||
interpreter. The directory/zipfile is automatically inserted as the
|
||
first entry in sys.path. (Suggestion and initial patch by Andy Chu;
|
||
revised patch by Phillip J. Eby and Nick Coghlan; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=1739468">bpo-1739468</a>.)</p></li>
|
||
<li><p>The <a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-func docutils literal notranslate"><span class="pre">int()</span></code></a> type gained a <code class="docutils literal notranslate"><span class="pre">bit_length</span></code> method that returns the
|
||
number of bits necessary to represent its argument in binary:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">n</span> <span class="o">=</span> <span class="mi">37</span>
|
||
<span class="gp">>>> </span><span class="nb">bin</span><span class="p">(</span><span class="mi">37</span><span class="p">)</span>
|
||
<span class="go">'0b100101'</span>
|
||
<span class="gp">>>> </span><span class="n">n</span><span class="o">.</span><span class="n">bit_length</span><span class="p">()</span>
|
||
<span class="go">6</span>
|
||
<span class="gp">>>> </span><span class="n">n</span> <span class="o">=</span> <span class="mi">2</span><span class="o">**</span><span class="mi">123</span><span class="o">-</span><span class="mi">1</span>
|
||
<span class="gp">>>> </span><span class="n">n</span><span class="o">.</span><span class="n">bit_length</span><span class="p">()</span>
|
||
<span class="go">123</span>
|
||
<span class="gp">>>> </span><span class="p">(</span><span class="n">n</span><span class="o">+</span><span class="mi">1</span><span class="p">)</span><span class="o">.</span><span class="n">bit_length</span><span class="p">()</span>
|
||
<span class="go">124</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>(Contributed by Fredrik Johansson, Victor Stinner, Raymond Hettinger,
|
||
and Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=3439">bpo-3439</a>.)</p>
|
||
</li>
|
||
<li><p>The fields in <a class="reference internal" href="../library/functions.html#format" title="format"><code class="xref py py-func docutils literal notranslate"><span class="pre">format()</span></code></a> strings can now be automatically
|
||
numbered:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s1">'Sir </span><span class="si">{}</span><span class="s1"> of </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">'Gallahad'</span><span class="p">,</span> <span class="s1">'Camelot'</span><span class="p">)</span>
|
||
<span class="go">'Sir Gallahad of Camelot'</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>Formerly, the string would have required numbered fields such as:
|
||
<code class="docutils literal notranslate"><span class="pre">'Sir</span> <span class="pre">{0}</span> <span class="pre">of</span> <span class="pre">{1}'</span></code>.</p>
|
||
<p>(Contributed by Eric Smith; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=5237">bpo-5237</a>.)</p>
|
||
</li>
|
||
<li><p>The <code class="xref py py-func docutils literal notranslate"><span class="pre">string.maketrans()</span></code> function is deprecated and is replaced by new
|
||
static methods, <a class="reference internal" href="../library/stdtypes.html#bytes.maketrans" title="bytes.maketrans"><code class="xref py py-meth docutils literal notranslate"><span class="pre">bytes.maketrans()</span></code></a> and <a class="reference internal" href="../library/stdtypes.html#bytearray.maketrans" title="bytearray.maketrans"><code class="xref py py-meth docutils literal notranslate"><span class="pre">bytearray.maketrans()</span></code></a>.
|
||
This change solves the confusion around which types were supported by the
|
||
<a class="reference internal" href="../library/string.html#module-string" title="string: Common string operations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">string</span></code></a> module. Now, <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a>, <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a>, and
|
||
<a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a> each have their own <strong>maketrans</strong> and <strong>translate</strong>
|
||
methods with intermediate translation tables of the appropriate type.</p>
|
||
<p>(Contributed by Georg Brandl; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=5675">bpo-5675</a>.)</p>
|
||
</li>
|
||
<li><p>The syntax of the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement now allows multiple context
|
||
managers in a single statement:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="k">with</span> <span class="nb">open</span><span class="p">(</span><span class="s1">'mylog.txt'</span><span class="p">)</span> <span class="k">as</span> <span class="n">infile</span><span class="p">,</span> <span class="nb">open</span><span class="p">(</span><span class="s1">'a.out'</span><span class="p">,</span> <span class="s1">'w'</span><span class="p">)</span> <span class="k">as</span> <span class="n">outfile</span><span class="p">:</span>
|
||
<span class="gp">... </span> <span class="k">for</span> <span class="n">line</span> <span class="ow">in</span> <span class="n">infile</span><span class="p">:</span>
|
||
<span class="gp">... </span> <span class="k">if</span> <span class="s1">'<critical>'</span> <span class="ow">in</span> <span class="n">line</span><span class="p">:</span>
|
||
<span class="gp">... </span> <span class="n">outfile</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">line</span><span class="p">)</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>With the new syntax, the <code class="xref py py-func docutils literal notranslate"><span class="pre">contextlib.nested()</span></code> function is no longer
|
||
needed and is now deprecated.</p>
|
||
<p>(Contributed by Georg Brandl and Mattias Brändström;
|
||
<a class="reference external" href="https://codereview.appspot.com/53094">appspot issue 53094</a>.)</p>
|
||
</li>
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">round(x,</span> <span class="pre">n)</span></code> now returns an integer if <em>x</em> is an integer.
|
||
Previously it returned a float:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="nb">round</span><span class="p">(</span><span class="mi">1123</span><span class="p">,</span> <span class="o">-</span><span class="mi">2</span><span class="p">)</span>
|
||
<span class="go">1100</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>(Contributed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=4707">bpo-4707</a>.)</p>
|
||
</li>
|
||
<li><p>Python now uses David Gay’s algorithm for finding the shortest floating-point
|
||
representation that doesn’t change its value. This should help
|
||
mitigate some of the confusion surrounding binary floating-point
|
||
numbers.</p>
|
||
<p>The significance is easily seen with a number like <code class="docutils literal notranslate"><span class="pre">1.1</span></code> which does not
|
||
have an exact equivalent in binary floating point. Since there is no exact
|
||
equivalent, an expression like <code class="docutils literal notranslate"><span class="pre">float('1.1')</span></code> evaluates to the nearest
|
||
representable value which is <code class="docutils literal notranslate"><span class="pre">0x1.199999999999ap+0</span></code> in hex or
|
||
<code class="docutils literal notranslate"><span class="pre">1.100000000000000088817841970012523233890533447265625</span></code> in decimal. That
|
||
nearest value was and still is used in subsequent floating-point
|
||
calculations.</p>
|
||
<p>What is new is how the number gets displayed. Formerly, Python used a
|
||
simple approach. The value of <code class="docutils literal notranslate"><span class="pre">repr(1.1)</span></code> was computed as <code class="docutils literal notranslate"><span class="pre">format(1.1,</span>
|
||
<span class="pre">'.17g')</span></code> which evaluated to <code class="docutils literal notranslate"><span class="pre">'1.1000000000000001'</span></code>. The advantage of
|
||
using 17 digits was that it relied on IEEE-754 guarantees to assure that
|
||
<code class="docutils literal notranslate"><span class="pre">eval(repr(1.1))</span></code> would round-trip exactly to its original value. The
|
||
disadvantage is that many people found the output to be confusing (mistaking
|
||
intrinsic limitations of binary floating-point representation as being a
|
||
problem with Python itself).</p>
|
||
<p>The new algorithm for <code class="docutils literal notranslate"><span class="pre">repr(1.1)</span></code> is smarter and returns <code class="docutils literal notranslate"><span class="pre">'1.1'</span></code>.
|
||
Effectively, it searches all equivalent string representations (ones that
|
||
get stored with the same underlying float value) and returns the shortest
|
||
representation.</p>
|
||
<p>The new algorithm tends to emit cleaner representations when possible, but
|
||
it does not change the underlying values. So, it is still the case that
|
||
<code class="docutils literal notranslate"><span class="pre">1.1</span> <span class="pre">+</span> <span class="pre">2.2</span> <span class="pre">!=</span> <span class="pre">3.3</span></code> even though the representations may suggest otherwise.</p>
|
||
<p>The new algorithm depends on certain features in the underlying floating-point
|
||
implementation. If the required features are not found, the old
|
||
algorithm will continue to be used. Also, the text pickle protocols
|
||
assure cross-platform portability by using the old algorithm.</p>
|
||
<p>(Contributed by Eric Smith and Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=1580">bpo-1580</a>)</p>
|
||
</li>
|
||
</ul>
|
||
</section>
|
||
<section id="new-improved-and-deprecated-modules">
|
||
<h2>New, Improved, and Deprecated Modules<a class="headerlink" href="#new-improved-and-deprecated-modules" title="Link to this heading">¶</a></h2>
|
||
<ul>
|
||
<li><p>Added a <a class="reference internal" href="../library/collections.html#collections.Counter" title="collections.Counter"><code class="xref py py-class docutils literal notranslate"><span class="pre">collections.Counter</span></code></a> class to support convenient
|
||
counting of unique items in a sequence or iterable:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">Counter</span><span class="p">([</span><span class="s1">'red'</span><span class="p">,</span> <span class="s1">'blue'</span><span class="p">,</span> <span class="s1">'red'</span><span class="p">,</span> <span class="s1">'green'</span><span class="p">,</span> <span class="s1">'blue'</span><span class="p">,</span> <span class="s1">'blue'</span><span class="p">])</span>
|
||
<span class="go">Counter({'blue': 3, 'red': 2, 'green': 1})</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>(Contributed by Raymond Hettinger; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=1696199">bpo-1696199</a>.)</p>
|
||
</li>
|
||
<li><p>Added a new module, <a class="reference internal" href="../library/tkinter.ttk.html#module-tkinter.ttk" title="tkinter.ttk: Tk themed widget set"><code class="xref py py-mod docutils literal notranslate"><span class="pre">tkinter.ttk</span></code></a> for access to the Tk themed widget set.
|
||
The basic idea of ttk is to separate, to the extent possible, the code
|
||
implementing a widget’s behavior from the code implementing its appearance.</p>
|
||
<p>(Contributed by Guilherme Polo; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=2983">bpo-2983</a>.)</p>
|
||
</li>
|
||
<li><p>The <a class="reference internal" href="../library/gzip.html#gzip.GzipFile" title="gzip.GzipFile"><code class="xref py py-class docutils literal notranslate"><span class="pre">gzip.GzipFile</span></code></a> and <a class="reference internal" href="../library/bz2.html#bz2.BZ2File" title="bz2.BZ2File"><code class="xref py py-class docutils literal notranslate"><span class="pre">bz2.BZ2File</span></code></a> classes now support
|
||
the context management protocol:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="c1"># Automatically close file after writing</span>
|
||
<span class="gp">>>> </span><span class="k">with</span> <span class="n">gzip</span><span class="o">.</span><span class="n">GzipFile</span><span class="p">(</span><span class="n">filename</span><span class="p">,</span> <span class="s2">"wb"</span><span class="p">)</span> <span class="k">as</span> <span class="n">f</span><span class="p">:</span>
|
||
<span class="gp">... </span> <span class="n">f</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="sa">b</span><span class="s2">"xxx"</span><span class="p">)</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>(Contributed by Antoine Pitrou.)</p>
|
||
</li>
|
||
<li><p>The <a class="reference internal" href="../library/decimal.html#module-decimal" title="decimal: Implementation of the General Decimal Arithmetic Specification."><code class="xref py py-mod docutils literal notranslate"><span class="pre">decimal</span></code></a> module now supports methods for creating a
|
||
decimal object from a binary <a class="reference internal" href="../library/functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a>. The conversion is
|
||
exact but can sometimes be surprising:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">Decimal</span><span class="o">.</span><span class="n">from_float</span><span class="p">(</span><span class="mf">1.1</span><span class="p">)</span>
|
||
<span class="go">Decimal('1.100000000000000088817841970012523233890533447265625')</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>The long decimal result shows the actual binary fraction being
|
||
stored for <em>1.1</em>. The fraction has many digits because <em>1.1</em> cannot
|
||
be exactly represented in binary.</p>
|
||
<p>(Contributed by Raymond Hettinger and Mark Dickinson.)</p>
|
||
</li>
|
||
<li><p>The <a class="reference internal" href="../library/itertools.html#module-itertools" title="itertools: Functions creating iterators for efficient looping."><code class="xref py py-mod docutils literal notranslate"><span class="pre">itertools</span></code></a> module grew two new functions. The
|
||
<a class="reference internal" href="../library/itertools.html#itertools.combinations_with_replacement" title="itertools.combinations_with_replacement"><code class="xref py py-func docutils literal notranslate"><span class="pre">itertools.combinations_with_replacement()</span></code></a> function is one of
|
||
four for generating combinatorics including permutations and Cartesian
|
||
products. The <a class="reference internal" href="../library/itertools.html#itertools.compress" title="itertools.compress"><code class="xref py py-func docutils literal notranslate"><span class="pre">itertools.compress()</span></code></a> function mimics its namesake
|
||
from APL. Also, the existing <a class="reference internal" href="../library/itertools.html#itertools.count" title="itertools.count"><code class="xref py py-func docutils literal notranslate"><span class="pre">itertools.count()</span></code></a> function now has
|
||
an optional <em>step</em> argument and can accept any type of counting
|
||
sequence including <a class="reference internal" href="../library/fractions.html#fractions.Fraction" title="fractions.Fraction"><code class="xref py py-class docutils literal notranslate"><span class="pre">fractions.Fraction</span></code></a> and
|
||
<a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">decimal.Decimal</span></code></a>:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="p">[</span><span class="n">p</span><span class="o">+</span><span class="n">q</span> <span class="k">for</span> <span class="n">p</span><span class="p">,</span><span class="n">q</span> <span class="ow">in</span> <span class="n">combinations_with_replacement</span><span class="p">(</span><span class="s1">'LOVE'</span><span class="p">,</span> <span class="mi">2</span><span class="p">)]</span>
|
||
<span class="go">['LL', 'LO', 'LV', 'LE', 'OO', 'OV', 'OE', 'VV', 'VE', 'EE']</span>
|
||
|
||
<span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">compress</span><span class="p">(</span><span class="n">data</span><span class="o">=</span><span class="nb">range</span><span class="p">(</span><span class="mi">10</span><span class="p">),</span> <span class="n">selectors</span><span class="o">=</span><span class="p">[</span><span class="mi">0</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="mi">1</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="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">]))</span>
|
||
<span class="go">[2, 3, 5, 7]</span>
|
||
|
||
<span class="gp">>>> </span><span class="n">c</span> <span class="o">=</span> <span class="n">count</span><span class="p">(</span><span class="n">start</span><span class="o">=</span><span class="n">Fraction</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">),</span> <span class="n">step</span><span class="o">=</span><span class="n">Fraction</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">6</span><span class="p">))</span>
|
||
<span class="gp">>>> </span><span class="p">[</span><span class="nb">next</span><span class="p">(</span><span class="n">c</span><span class="p">),</span> <span class="nb">next</span><span class="p">(</span><span class="n">c</span><span class="p">),</span> <span class="nb">next</span><span class="p">(</span><span class="n">c</span><span class="p">),</span> <span class="nb">next</span><span class="p">(</span><span class="n">c</span><span class="p">)]</span>
|
||
<span class="go">[Fraction(1, 2), Fraction(2, 3), Fraction(5, 6), Fraction(1, 1)]</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>(Contributed by Raymond Hettinger.)</p>
|
||
</li>
|
||
<li><p><a class="reference internal" href="../library/collections.html#collections.namedtuple" title="collections.namedtuple"><code class="xref py py-func docutils literal notranslate"><span class="pre">collections.namedtuple()</span></code></a> now supports a keyword argument
|
||
<em>rename</em> which lets invalid fieldnames be automatically converted to
|
||
positional names in the form _0, _1, etc. This is useful when
|
||
the field names are being created by an external source such as a
|
||
CSV header, SQL field list, or user input:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">query</span> <span class="o">=</span> <span class="nb">input</span><span class="p">()</span>
|
||
<span class="go">SELECT region, dept, count(*) FROM main GROUPBY region, dept</span>
|
||
|
||
<span class="gp">>>> </span><span class="n">cursor</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="n">query</span><span class="p">)</span>
|
||
<span class="gp">>>> </span><span class="n">query_fields</span> <span class="o">=</span> <span class="p">[</span><span class="n">desc</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="k">for</span> <span class="n">desc</span> <span class="ow">in</span> <span class="n">cursor</span><span class="o">.</span><span class="n">description</span><span class="p">]</span>
|
||
<span class="gp">>>> </span><span class="n">UserQuery</span> <span class="o">=</span> <span class="n">namedtuple</span><span class="p">(</span><span class="s1">'UserQuery'</span><span class="p">,</span> <span class="n">query_fields</span><span class="p">,</span> <span class="n">rename</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
|
||
<span class="gp">>>> </span><span class="n">pprint</span><span class="o">.</span><span class="n">pprint</span><span class="p">([</span><span class="n">UserQuery</span><span class="p">(</span><span class="o">*</span><span class="n">row</span><span class="p">)</span> <span class="k">for</span> <span class="n">row</span> <span class="ow">in</span> <span class="n">cursor</span><span class="p">])</span>
|
||
<span class="go">[UserQuery(region='South', dept='Shipping', _2=185),</span>
|
||
<span class="go"> UserQuery(region='North', dept='Accounting', _2=37),</span>
|
||
<span class="go"> UserQuery(region='West', dept='Sales', _2=419)]</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>(Contributed by Raymond Hettinger; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=1818">bpo-1818</a>.)</p>
|
||
</li>
|
||
<li><p>The <a class="reference internal" href="../library/re.html#re.sub" title="re.sub"><code class="xref py py-func docutils literal notranslate"><span class="pre">re.sub()</span></code></a>, <a class="reference internal" href="../library/re.html#re.subn" title="re.subn"><code class="xref py py-func docutils literal notranslate"><span class="pre">re.subn()</span></code></a> and <a class="reference internal" href="../library/re.html#re.split" title="re.split"><code class="xref py py-func docutils literal notranslate"><span class="pre">re.split()</span></code></a> functions now
|
||
accept a flags parameter.</p>
|
||
<p>(Contributed by Gregory Smith.)</p>
|
||
</li>
|
||
<li><p>The <a class="reference internal" href="../library/logging.html#module-logging" title="logging: Flexible event logging system for applications."><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging</span></code></a> module now implements a simple <a class="reference internal" href="../library/logging.handlers.html#logging.NullHandler" title="logging.NullHandler"><code class="xref py py-class docutils literal notranslate"><span class="pre">logging.NullHandler</span></code></a>
|
||
class for applications that are not using logging but are calling
|
||
library code that does. Setting-up a null handler will suppress
|
||
spurious warnings such as “No handlers could be found for logger foo”:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">h</span> <span class="o">=</span> <span class="n">logging</span><span class="o">.</span><span class="n">NullHandler</span><span class="p">()</span>
|
||
<span class="gp">>>> </span><span class="n">logging</span><span class="o">.</span><span class="n">getLogger</span><span class="p">(</span><span class="s2">"foo"</span><span class="p">)</span><span class="o">.</span><span class="n">addHandler</span><span class="p">(</span><span class="n">h</span><span class="p">)</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>(Contributed by Vinay Sajip; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=4384">bpo-4384</a>).</p>
|
||
</li>
|
||
<li><p>The <a class="reference internal" href="../library/runpy.html#module-runpy" title="runpy: Locate and run Python modules without importing them first."><code class="xref py py-mod docutils literal notranslate"><span class="pre">runpy</span></code></a> module which supports the <code class="docutils literal notranslate"><span class="pre">-m</span></code> command line switch
|
||
now supports the execution of packages by looking for and executing
|
||
a <code class="docutils literal notranslate"><span class="pre">__main__</span></code> submodule when a package name is supplied.</p>
|
||
<p>(Contributed by Andi Vajda; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=4195">bpo-4195</a>.)</p>
|
||
</li>
|
||
<li><p>The <a class="reference internal" href="../library/pdb.html#module-pdb" title="pdb: The Python debugger for interactive interpreters."><code class="xref py py-mod docutils literal notranslate"><span class="pre">pdb</span></code></a> module can now access and display source code loaded via
|
||
<a class="reference internal" href="../library/zipimport.html#module-zipimport" title="zipimport: Support for importing Python modules from ZIP archives."><code class="xref py py-mod docutils literal notranslate"><span class="pre">zipimport</span></code></a> (or any other conformant <span class="target" id="index-2"></span><a class="pep reference external" href="https://peps.python.org/pep-0302/"><strong>PEP 302</strong></a> loader).</p>
|
||
<p>(Contributed by Alexander Belopolsky; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=4201">bpo-4201</a>.)</p>
|
||
</li>
|
||
<li><p><a class="reference internal" href="../library/functools.html#functools.partial" title="functools.partial"><code class="xref py py-class docutils literal notranslate"><span class="pre">functools.partial</span></code></a> objects can now be pickled.</p></li>
|
||
</ul>
|
||
<blockquote>
|
||
<div><p>(Suggested by Antoine Pitrou and Jesse Noller. Implemented by
|
||
Jack Diederich; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=5228">bpo-5228</a>.)</p>
|
||
</div></blockquote>
|
||
<ul>
|
||
<li><p>Add <a class="reference internal" href="../library/pydoc.html#module-pydoc" title="pydoc: Documentation generator and online help system."><code class="xref py py-mod docutils literal notranslate"><span class="pre">pydoc</span></code></a> help topics for symbols so that <code class="docutils literal notranslate"><span class="pre">help('@')</span></code>
|
||
works as expected in the interactive environment.</p>
|
||
<p>(Contributed by David Laban; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=4739">bpo-4739</a>.)</p>
|
||
</li>
|
||
<li><p>The <a class="reference internal" href="../library/unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate"><span class="pre">unittest</span></code></a> module now supports skipping individual tests or classes
|
||
of tests. And it supports marking a test as an expected failure, a test that
|
||
is known to be broken, but shouldn’t be counted as a failure on a
|
||
TestResult:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">class</span><span class="w"> </span><span class="nc">TestGizmo</span><span class="p">(</span><span class="n">unittest</span><span class="o">.</span><span class="n">TestCase</span><span class="p">):</span>
|
||
|
||
<span class="nd">@unittest</span><span class="o">.</span><span class="n">skipUnless</span><span class="p">(</span><span class="n">sys</span><span class="o">.</span><span class="n">platform</span><span class="o">.</span><span class="n">startswith</span><span class="p">(</span><span class="s2">"win"</span><span class="p">),</span> <span class="s2">"requires Windows"</span><span class="p">)</span>
|
||
<span class="k">def</span><span class="w"> </span><span class="nf">test_gizmo_on_windows</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
|
||
<span class="o">...</span>
|
||
|
||
<span class="nd">@unittest</span><span class="o">.</span><span class="n">expectedFailure</span>
|
||
<span class="k">def</span><span class="w"> </span><span class="nf">test_gimzo_without_required_library</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
|
||
<span class="o">...</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>Also, tests for exceptions have been builtout to work with context managers
|
||
using the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span><span class="w"> </span><span class="nf">test_division_by_zero</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
|
||
<span class="k">with</span> <span class="bp">self</span><span class="o">.</span><span class="n">assertRaises</span><span class="p">(</span><span class="ne">ZeroDivisionError</span><span class="p">):</span>
|
||
<span class="n">x</span> <span class="o">/</span> <span class="mi">0</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>In addition, several new assertion methods were added including
|
||
<a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertSetEqual" title="unittest.TestCase.assertSetEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertSetEqual()</span></code></a>,
|
||
<a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertDictEqual" title="unittest.TestCase.assertDictEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertDictEqual()</span></code></a>,
|
||
<code class="xref py py-meth docutils literal notranslate"><span class="pre">assertDictContainsSubset()</span></code>,
|
||
<a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertListEqual" title="unittest.TestCase.assertListEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertListEqual()</span></code></a>,
|
||
<a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertTupleEqual" title="unittest.TestCase.assertTupleEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertTupleEqual()</span></code></a>,
|
||
<a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertSequenceEqual" title="unittest.TestCase.assertSequenceEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertSequenceEqual()</span></code></a>,
|
||
<a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertRaisesRegex" title="unittest.TestCase.assertRaisesRegex"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertRaisesRegexp()</span></code></a>,
|
||
<a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertIsNone" title="unittest.TestCase.assertIsNone"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertIsNone()</span></code></a>,
|
||
and <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertIsNotNone" title="unittest.TestCase.assertIsNotNone"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertIsNotNone()</span></code></a>.</p>
|
||
<p>(Contributed by Benjamin Peterson and Antoine Pitrou.)</p>
|
||
</li>
|
||
<li><p>The <a class="reference internal" href="../library/io.html#module-io" title="io: Core tools for working with streams."><code class="xref py py-mod docutils literal notranslate"><span class="pre">io</span></code></a> module has three new constants for the <a class="reference internal" href="../library/io.html#io.IOBase.seek" title="io.IOBase.seek"><code class="xref py py-meth docutils literal notranslate"><span class="pre">seek()</span></code></a>
|
||
method: <a class="reference internal" href="../library/os.html#os.SEEK_SET" title="os.SEEK_SET"><code class="xref py py-data docutils literal notranslate"><span class="pre">SEEK_SET</span></code></a>, <a class="reference internal" href="../library/os.html#os.SEEK_CUR" title="os.SEEK_CUR"><code class="xref py py-data docutils literal notranslate"><span class="pre">SEEK_CUR</span></code></a>, and <a class="reference internal" href="../library/os.html#os.SEEK_END" title="os.SEEK_END"><code class="xref py py-data docutils literal notranslate"><span class="pre">SEEK_END</span></code></a>.</p></li>
|
||
<li><p>The <a class="reference internal" href="../library/sys.html#sys.version_info" title="sys.version_info"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.version_info</span></code></a> tuple is now a named tuple:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">sys</span><span class="o">.</span><span class="n">version_info</span>
|
||
<span class="go">sys.version_info(major=3, minor=1, micro=0, releaselevel='alpha', serial=2)</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>(Contributed by Ross Light; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=4285">bpo-4285</a>.)</p>
|
||
</li>
|
||
<li><p>The <code class="xref py py-mod docutils literal notranslate"><span class="pre">nntplib</span></code> and <a class="reference internal" href="../library/imaplib.html#module-imaplib" title="imaplib: IMAP4 protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate"><span class="pre">imaplib</span></code></a> modules now support IPv6.</p>
|
||
<p>(Contributed by Derek Morr; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=1655">bpo-1655</a> and <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=1664">bpo-1664</a>.)</p>
|
||
</li>
|
||
<li><p>The <a class="reference internal" href="../library/pickle.html#module-pickle" title="pickle: Convert Python objects to streams of bytes and back."><code class="xref py py-mod docutils literal notranslate"><span class="pre">pickle</span></code></a> module has been adapted for better interoperability with
|
||
Python 2.x when used with protocol 2 or lower. The reorganization of the
|
||
standard library changed the formal reference for many objects. For
|
||
example, <code class="docutils literal notranslate"><span class="pre">__builtin__.set</span></code> in Python 2 is called <code class="docutils literal notranslate"><span class="pre">builtins.set</span></code> in Python
|
||
3. This change confounded efforts to share data between different versions of
|
||
Python. But now when protocol 2 or lower is selected, the pickler will
|
||
automatically use the old Python 2 names for both loading and dumping. This
|
||
remapping is turned-on by default but can be disabled with the <em>fix_imports</em>
|
||
option:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">s</span> <span class="o">=</span> <span class="p">{</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">}</span>
|
||
<span class="gp">>>> </span><span class="n">pickle</span><span class="o">.</span><span class="n">dumps</span><span class="p">(</span><span class="n">s</span><span class="p">,</span> <span class="n">protocol</span><span class="o">=</span><span class="mi">0</span><span class="p">)</span>
|
||
<span class="go">b'c__builtin__\nset\np0\n((lp1\nL1L\naL2L\naL3L\natp2\nRp3\n.'</span>
|
||
<span class="gp">>>> </span><span class="n">pickle</span><span class="o">.</span><span class="n">dumps</span><span class="p">(</span><span class="n">s</span><span class="p">,</span> <span class="n">protocol</span><span class="o">=</span><span class="mi">0</span><span class="p">,</span> <span class="n">fix_imports</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span>
|
||
<span class="go">b'cbuiltins\nset\np0\n((lp1\nL1L\naL2L\naL3L\natp2\nRp3\n.'</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>An unfortunate but unavoidable side-effect of this change is that protocol 2
|
||
pickles produced by Python 3.1 won’t be readable with Python 3.0. The latest
|
||
pickle protocol, protocol 3, should be used when migrating data between
|
||
Python 3.x implementations, as it doesn’t attempt to remain compatible with
|
||
Python 2.x.</p>
|
||
<p>(Contributed by Alexandre Vassalotti and Antoine Pitrou, <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=6137">bpo-6137</a>.)</p>
|
||
</li>
|
||
<li><p>A new module, <a class="reference internal" href="../library/importlib.html#module-importlib" title="importlib: The implementation of the import machinery."><code class="xref py py-mod docutils literal notranslate"><span class="pre">importlib</span></code></a> was added. It provides a complete, portable,
|
||
pure Python reference implementation of the <a class="reference internal" href="../reference/simple_stmts.html#import"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">import</span></code></a> statement and its
|
||
counterpart, the <a class="reference internal" href="../library/functions.html#import__" title="__import__"><code class="xref py py-func docutils literal notranslate"><span class="pre">__import__()</span></code></a> function. It represents a substantial
|
||
step forward in documenting and defining the actions that take place during
|
||
imports.</p>
|
||
<p>(Contributed by Brett Cannon.)</p>
|
||
</li>
|
||
</ul>
|
||
</section>
|
||
<section id="optimizations">
|
||
<h2>Optimizations<a class="headerlink" href="#optimizations" title="Link to this heading">¶</a></h2>
|
||
<p>Major performance enhancements have been added:</p>
|
||
<ul>
|
||
<li><p>The new I/O library (as defined in <span class="target" id="index-3"></span><a class="pep reference external" href="https://peps.python.org/pep-3116/"><strong>PEP 3116</strong></a>) was mostly written in
|
||
Python and quickly proved to be a problematic bottleneck in Python 3.0.
|
||
In Python 3.1, the I/O library has been entirely rewritten in C and is
|
||
2 to 20 times faster depending on the task at hand. The pure Python
|
||
version is still available for experimentation purposes through
|
||
the <code class="docutils literal notranslate"><span class="pre">_pyio</span></code> module.</p>
|
||
<p>(Contributed by Amaury Forgeot d’Arc and Antoine Pitrou.)</p>
|
||
</li>
|
||
<li><p>Added a heuristic so that tuples and dicts containing only untrackable objects
|
||
are not tracked by the garbage collector. This can reduce the size of
|
||
collections and therefore the garbage collection overhead on long-running
|
||
programs, depending on their particular use of datatypes.</p>
|
||
<p>(Contributed by Antoine Pitrou, <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=4688">bpo-4688</a>.)</p>
|
||
</li>
|
||
<li><p>Enabling a configure option named <code class="docutils literal notranslate"><span class="pre">--with-computed-gotos</span></code>
|
||
on compilers that support it (notably: gcc, SunPro, icc), the bytecode
|
||
evaluation loop is compiled with a new dispatch mechanism which gives
|
||
speedups of up to 20%, depending on the system, the compiler, and
|
||
the benchmark.</p>
|
||
<p>(Contributed by Antoine Pitrou along with a number of other participants,
|
||
<a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=4753">bpo-4753</a>).</p>
|
||
</li>
|
||
<li><p>The decoding of UTF-8, UTF-16 and LATIN-1 is now two to four times
|
||
faster.</p>
|
||
<p>(Contributed by Antoine Pitrou and Amaury Forgeot d’Arc, <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=4868">bpo-4868</a>.)</p>
|
||
</li>
|
||
<li><p>The <a class="reference internal" href="../library/json.html#module-json" title="json: Encode and decode the JSON format."><code class="xref py py-mod docutils literal notranslate"><span class="pre">json</span></code></a> module now has a C extension to substantially improve
|
||
its performance. In addition, the API was modified so that json works
|
||
only with <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a>, not with <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a>. That change makes the
|
||
module closely match the <a class="reference external" href="https://json.org/">JSON specification</a>
|
||
which is defined in terms of Unicode.</p>
|
||
<p>(Contributed by Bob Ippolito and converted to Py3.1 by Antoine Pitrou
|
||
and Benjamin Peterson; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=4136">bpo-4136</a>.)</p>
|
||
</li>
|
||
<li><p>Unpickling now interns the attribute names of pickled objects. This saves
|
||
memory and allows pickles to be smaller.</p>
|
||
<p>(Contributed by Jake McGuire and Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=5084">bpo-5084</a>.)</p>
|
||
</li>
|
||
</ul>
|
||
</section>
|
||
<section id="idle">
|
||
<h2>IDLE<a class="headerlink" href="#idle" title="Link to this heading">¶</a></h2>
|
||
<ul>
|
||
<li><p>IDLE’s format menu now provides an option to strip trailing whitespace
|
||
from a source file.</p>
|
||
<p>(Contributed by Roger D. Serwy; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=5150">bpo-5150</a>.)</p>
|
||
</li>
|
||
</ul>
|
||
</section>
|
||
<section id="build-and-c-api-changes">
|
||
<h2>Build and C API Changes<a class="headerlink" href="#build-and-c-api-changes" title="Link to this heading">¶</a></h2>
|
||
<p>Changes to Python’s build process and to the C API include:</p>
|
||
<ul>
|
||
<li><p>Integers are now stored internally either in base <code class="docutils literal notranslate"><span class="pre">2**15</span></code> or in base
|
||
<code class="docutils literal notranslate"><span class="pre">2**30</span></code>, the base being determined at build time. Previously, they
|
||
were always stored in base <code class="docutils literal notranslate"><span class="pre">2**15</span></code>. Using base <code class="docutils literal notranslate"><span class="pre">2**30</span></code> gives
|
||
significant performance improvements on 64-bit machines, but
|
||
benchmark results on 32-bit machines have been mixed. Therefore,
|
||
the default is to use base <code class="docutils literal notranslate"><span class="pre">2**30</span></code> on 64-bit machines and base <code class="docutils literal notranslate"><span class="pre">2**15</span></code>
|
||
on 32-bit machines; on Unix, there’s a new configure option
|
||
<code class="docutils literal notranslate"><span class="pre">--enable-big-digits</span></code> that can be used to override this default.</p>
|
||
<p>Apart from the performance improvements this change should be invisible to
|
||
end users, with one exception: for testing and debugging purposes there’s a
|
||
new <a class="reference internal" href="../library/sys.html#sys.int_info" title="sys.int_info"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.int_info</span></code></a> that provides information about the
|
||
internal format, giving the number of bits per digit and the size in bytes
|
||
of the C type used to store each digit:</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">sys</span>
|
||
<span class="gp">>>> </span><span class="n">sys</span><span class="o">.</span><span class="n">int_info</span>
|
||
<span class="go">sys.int_info(bits_per_digit=30, sizeof_digit=4)</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>(Contributed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=4258">bpo-4258</a>.)</p>
|
||
</li>
|
||
<li><p>The <a class="reference internal" href="../c-api/long.html#c.PyLong_AsUnsignedLongLong" title="PyLong_AsUnsignedLongLong"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyLong_AsUnsignedLongLong()</span></code></a> function now handles a negative
|
||
<em>pylong</em> by raising <a class="reference internal" href="../library/exceptions.html#OverflowError" title="OverflowError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OverflowError</span></code></a> instead of <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a>.</p>
|
||
<p>(Contributed by Mark Dickinson and Lisandro Dalcrin; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=5175">bpo-5175</a>.)</p>
|
||
</li>
|
||
<li><p>Deprecated <code class="xref c c-func docutils literal notranslate"><span class="pre">PyNumber_Int()</span></code>. Use <a class="reference internal" href="../c-api/number.html#c.PyNumber_Long" title="PyNumber_Long"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyNumber_Long()</span></code></a> instead.</p>
|
||
<p>(Contributed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=4910">bpo-4910</a>.)</p>
|
||
</li>
|
||
<li><p>Added a new <a class="reference internal" href="../c-api/conversion.html#c.PyOS_string_to_double" title="PyOS_string_to_double"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyOS_string_to_double()</span></code></a> function to replace the
|
||
deprecated functions <code class="xref c c-func docutils literal notranslate"><span class="pre">PyOS_ascii_strtod()</span></code> and <code class="xref c c-func docutils literal notranslate"><span class="pre">PyOS_ascii_atof()</span></code>.</p>
|
||
<p>(Contributed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=5914">bpo-5914</a>.)</p>
|
||
</li>
|
||
<li><p>Added <a class="reference internal" href="../c-api/capsule.html#c.PyCapsule" title="PyCapsule"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyCapsule</span></code></a> as a replacement for the <code class="xref c c-type docutils literal notranslate"><span class="pre">PyCObject</span></code> API.
|
||
The principal difference is that the new type has a well defined interface
|
||
for passing typing safety information and a less complicated signature
|
||
for calling a destructor. The old type had a problematic API and is now
|
||
deprecated.</p>
|
||
<p>(Contributed by Larry Hastings; <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=5630">bpo-5630</a>.)</p>
|
||
</li>
|
||
</ul>
|
||
</section>
|
||
<section id="porting-to-python-3-1">
|
||
<h2>Porting to Python 3.1<a class="headerlink" href="#porting-to-python-3-1" title="Link to this heading">¶</a></h2>
|
||
<p>This section lists previously described changes and other bugfixes
|
||
that may require changes to your code:</p>
|
||
<ul>
|
||
<li><p>The new floating-point string representations can break existing doctests.
|
||
For example:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span><span class="w"> </span><span class="nf">e</span><span class="p">():</span>
|
||
<span class="w"> </span><span class="sd">'''Compute the base of natural logarithms.</span>
|
||
|
||
<span class="sd"> >>> e()</span>
|
||
<span class="sd"> 2.7182818284590451</span>
|
||
|
||
<span class="sd"> '''</span>
|
||
<span class="k">return</span> <span class="nb">sum</span><span class="p">(</span><span class="mi">1</span><span class="o">/</span><span class="n">math</span><span class="o">.</span><span class="n">factorial</span><span class="p">(</span><span class="n">x</span><span class="p">)</span> <span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="nb">reversed</span><span class="p">(</span><span class="nb">range</span><span class="p">(</span><span class="mi">30</span><span class="p">)))</span>
|
||
|
||
<span class="n">doctest</span><span class="o">.</span><span class="n">testmod</span><span class="p">()</span>
|
||
|
||
<span class="o">**********************************************************************</span>
|
||
<span class="n">Failed</span> <span class="n">example</span><span class="p">:</span>
|
||
<span class="n">e</span><span class="p">()</span>
|
||
<span class="n">Expected</span><span class="p">:</span>
|
||
<span class="mf">2.7182818284590451</span>
|
||
<span class="n">Got</span><span class="p">:</span>
|
||
<span class="mf">2.718281828459045</span>
|
||
<span class="o">**********************************************************************</span>
|
||
</pre></div>
|
||
</div>
|
||
</li>
|
||
<li><p>The automatic name remapping in the pickle module for protocol 2 or lower can
|
||
make Python 3.1 pickles unreadable in Python 3.0. One solution is to use
|
||
protocol 3. Another solution is to set the <em>fix_imports</em> option to <code class="docutils literal notranslate"><span class="pre">False</span></code>.
|
||
See the discussion above for more details.</p></li>
|
||
</ul>
|
||
</section>
|
||
</section>
|
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|
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<li><a class="reference internal" href="#">What’s New In Python 3.1</a><ul>
|
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<li><a class="reference internal" href="#pep-372-ordered-dictionaries">PEP 372: Ordered Dictionaries</a></li>
|
||
<li><a class="reference internal" href="#pep-378-format-specifier-for-thousands-separator">PEP 378: Format Specifier for Thousands Separator</a></li>
|
||
<li><a class="reference internal" href="#other-language-changes">Other Language Changes</a></li>
|
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<li><a class="reference internal" href="#new-improved-and-deprecated-modules">New, Improved, and Deprecated Modules</a></li>
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|
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<li><a class="reference internal" href="#idle">IDLE</a></li>
|
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<li><a class="reference internal" href="#build-and-c-api-changes">Build and C API Changes</a></li>
|
||
<li><a class="reference internal" href="#porting-to-python-3-1">Porting to Python 3.1</a></li>
|
||
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