Edit File: 2to3.html
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Development Tools</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="to3-automated-python-2-to-3-code-translation"> <span id="to3-reference"></span><h1>25.4. 2to3 - Automated Python 2 to 3 code translation<a class="headerlink" href="#to3-automated-python-2-to-3-code-translation" title="Permalink to this headline">¶</a></h1> <p>2to3 is a Python program that reads Python 2.x source code and applies a series of <em>fixers</em> to transform it into valid Python 3.x code. The standard library contains a rich set of fixers that will handle almost all code. 2to3 supporting library <a class="reference internal" href="#module-lib2to3" title="lib2to3: the 2to3 library"><tt class="xref py py-mod docutils literal"><span class="pre">lib2to3</span></tt></a> is, however, a flexible and generic library, so it is possible to write your own fixers for 2to3. <a class="reference internal" href="#module-lib2to3" title="lib2to3: the 2to3 library"><tt class="xref py py-mod docutils literal"><span class="pre">lib2to3</span></tt></a> could also be adapted to custom applications in which Python code needs to be edited automatically.</p> <div class="section" id="using-2to3"> <span id="to3-using"></span><h2>25.4.1. Using 2to3<a class="headerlink" href="#using-2to3" title="Permalink to this headline">¶</a></h2> <p>2to3 will usually be installed with the Python interpreter as a script. It is also located in the <tt class="file docutils literal"><span class="pre">Tools/scripts</span></tt> directory of the Python root.</p> <p>2to3’s basic arguments are a list of files or directories to transform. The directories are recursively traversed for Python sources.</p> <p>Here is a sample Python 2.x source file, <tt class="file docutils literal"><span class="pre">example.py</span></tt>:</p> <div class="highlight-python"><div class="highlight"><pre><span class="k">def</span> <span class="nf">greet</span><span class="p">(</span><span class="n">name</span><span class="p">):</span> <span class="k">print</span> <span class="s">"Hello, {0}!"</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">name</span><span class="p">)</span> <span class="k">print</span> <span class="s">"What's your name?"</span> <span class="n">name</span> <span class="o">=</span> <span class="nb">raw_input</span><span class="p">()</span> <span class="n">greet</span><span class="p">(</span><span class="n">name</span><span class="p">)</span> </pre></div> </div> <p>It can be converted to Python 3.x code via 2to3 on the command line:</p> <div class="highlight-python"><pre>$ 2to3 example.py</pre> </div> <p>A diff against the original source file is printed. 2to3 can also write the needed modifications right back to the source file. (A backup of the original file is made unless <em class="xref std std-option">-n</em> is also given.) Writing the changes back is enabled with the <em class="xref std std-option">-w</em> flag:</p> <div class="highlight-python"><pre>$ 2to3 -w example.py</pre> </div> <p>After transformation, <tt class="file docutils literal"><span class="pre">example.py</span></tt> looks like this:</p> <div class="highlight-python"><div class="highlight"><pre><span class="k">def</span> <span class="nf">greet</span><span class="p">(</span><span class="n">name</span><span class="p">):</span> <span class="k">print</span><span class="p">(</span><span class="s">"Hello, {0}!"</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">name</span><span class="p">))</span> <span class="k">print</span><span class="p">(</span><span class="s">"What's your name?"</span><span class="p">)</span> <span class="n">name</span> <span class="o">=</span> <span class="nb">input</span><span class="p">()</span> <span class="n">greet</span><span class="p">(</span><span class="n">name</span><span class="p">)</span> </pre></div> </div> <p>Comments and exact indentation are preserved throughout the translation process.</p> <p>By default, 2to3 runs a set of <a class="reference internal" href="#to3-fixers"><em>predefined fixers</em></a>. The <em class="xref std std-option">-l</em> flag lists all available fixers. An explicit set of fixers to run can be given with <em class="xref std std-option">-f</em>. Likewise the <a class="reference internal" href="../using/cmdline.html#cmdoption-x"><em class="xref std std-option">-x</em></a> explicitly disables a fixer. The following example runs only the <tt class="docutils literal"><span class="pre">imports</span></tt> and <tt class="docutils literal"><span class="pre">has_key</span></tt> fixers:</p> <div class="highlight-python"><pre>$ 2to3 -f imports -f has_key example.py</pre> </div> <p>This command runs every fixer except the <tt class="docutils literal"><span class="pre">apply</span></tt> fixer:</p> <div class="highlight-python"><pre>$ 2to3 -x apply example.py</pre> </div> <p>Some fixers are <em>explicit</em>, meaning they aren’t run by default and must be listed on the command line to be run. Here, in addition to the default fixers, the <tt class="docutils literal"><span class="pre">idioms</span></tt> fixer is run:</p> <div class="highlight-python"><pre>$ 2to3 -f all -f idioms example.py</pre> </div> <p>Notice how passing <tt class="docutils literal"><span class="pre">all</span></tt> enables all default fixers.</p> <p>Sometimes 2to3 will find a place in your source code that needs to be changed, but 2to3 cannot fix automatically. In this case, 2to3 will print a warning beneath the diff for a file. You should address the warning in order to have compliant 3.x code.</p> <p>2to3 can also refactor doctests. To enable this mode, use the <a class="reference internal" href="../using/cmdline.html#cmdoption-d"><em class="xref std std-option">-d</em></a> flag. Note that <em>only</em> doctests will be refactored. This also doesn’t require the module to be valid Python. For example, doctest like examples in a reST document could also be refactored with this option.</p> <p>The <a class="reference internal" href="../using/cmdline.html#cmdoption-v"><em class="xref std std-option">-v</em></a> option enables output of more information on the translation process.</p> <p>Since some print statements can be parsed as function calls or statements, 2to3 cannot always read files containing the print function. When 2to3 detects the presence of the <tt class="docutils literal"><span class="pre">from</span> <span class="pre">__future__</span> <span class="pre">import</span> <span class="pre">print_function</span></tt> compiler directive, it modifies its internal grammar to interpret <a class="reference internal" href="functions.html#print" title="print"><tt class="xref py py-func docutils literal"><span class="pre">print()</span></tt></a> as a function. This change can also be enabled manually with the <em class="xref std std-option">-p</em> flag. Use <em class="xref std std-option">-p</em> to run fixers on code that already has had its print statements converted.</p> <p>The <em class="xref std std-option">-o</em> or <em class="xref std std-option">--output-dir</em> option allows specification of an alternate directory for processed output files to be written to. The <em class="xref std std-option">-n</em> flag is required when using this as backup files do not make sense when not overwriting the input files.</p> <p class="versionadded"> <span class="versionmodified">New in version 2.7.3: </span>The <em class="xref std std-option">-o</em> option was added.</p> <p>The <a class="reference internal" href="../using/cmdline.html#cmdoption-W"><em class="xref std std-option">-W</em></a> or <em class="xref std std-option">--write-unchanged-files</em> flag tells 2to3 to always write output files even if no changes were required to the file. This is most useful with <em class="xref std std-option">-o</em> so that an entire Python source tree is copied with translation from one directory to another. This option implies the <em class="xref std std-option">-w</em> flag as it would not make sense otherwise.</p> <p class="versionadded"> <span class="versionmodified">New in version 2.7.3: </span>The <a class="reference internal" href="../using/cmdline.html#cmdoption-W"><em class="xref std std-option">-W</em></a> flag was added.</p> <p>The <em class="xref std std-option">--add-suffix</em> option specifies a string to append to all output filenames. The <em class="xref std std-option">-n</em> flag is required when specifying this as backups are not necessary when writing to different filenames. Example:</p> <div class="highlight-python"><pre>$ 2to3 -n -W --add-suffix=3 example.py</pre> </div> <p>Will cause a converted file named <tt class="docutils literal"><span class="pre">example.py3</span></tt> to be written.</p> <p class="versionadded"> <span class="versionmodified">New in version 2.7.3: </span>The <em class="xref std std-option">--add-suffix</em> option was added.</p> <p>To translate an entire project from one directory tree to another use:</p> <div class="highlight-python"><pre>$ 2to3 --output-dir=python3-version/mycode -W -n python2-version/mycode</pre> </div> </div> <div class="section" id="fixers"> <span id="to3-fixers"></span><h2>25.4.2. Fixers<a class="headerlink" href="#fixers" title="Permalink to this headline">¶</a></h2> <p>Each step of transforming code is encapsulated in a fixer. The command <tt class="docutils literal"><span class="pre">2to3</span> <span class="pre">-l</span></tt> lists them. As <a class="reference internal" href="#to3-using"><em>documented above</em></a>, each can be turned on and off individually. They are described here in more detail.</p> <dl class="2to3fixer"> <dt id="2to3fixer-apply"> <tt class="descname">apply</tt><a class="headerlink" href="#2to3fixer-apply" title="Permalink to this definition">¶</a></dt> <dd><p>Removes usage of <a class="reference internal" href="functions.html#apply" title="apply"><tt class="xref py py-func docutils literal"><span class="pre">apply()</span></tt></a>. For example <tt class="docutils literal"><span class="pre">apply(function,</span> <span class="pre">*args,</span> <span class="pre">**kwargs)</span></tt> is converted to <tt class="docutils literal"><span class="pre">function(*args,</span> <span class="pre">**kwargs)</span></tt>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-basestring"> <tt class="descname">basestring</tt><a class="headerlink" href="#2to3fixer-basestring" title="Permalink to this definition">¶</a></dt> <dd><p>Converts <a class="reference internal" href="functions.html#basestring" title="basestring"><tt class="xref py py-class docutils literal"><span class="pre">basestring</span></tt></a> to <a class="reference internal" href="functions.html#str" title="str"><tt class="xref py py-class docutils literal"><span class="pre">str</span></tt></a>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-buffer"> <tt class="descname">buffer</tt><a class="headerlink" href="#2to3fixer-buffer" title="Permalink to this definition">¶</a></dt> <dd><p>Converts <a class="reference internal" href="functions.html#buffer" title="buffer"><tt class="xref py py-class docutils literal"><span class="pre">buffer</span></tt></a> to <a class="reference internal" href="stdtypes.html#memoryview" title="memoryview"><tt class="xref py py-class docutils literal"><span class="pre">memoryview</span></tt></a>. This fixer is optional because the <a class="reference internal" href="stdtypes.html#memoryview" title="memoryview"><tt class="xref py py-class docutils literal"><span class="pre">memoryview</span></tt></a> API is similar but not exactly the same as that of <a class="reference internal" href="functions.html#buffer" title="buffer"><tt class="xref py py-class docutils literal"><span class="pre">buffer</span></tt></a>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-callable"> <tt class="descname">callable</tt><a class="headerlink" href="#2to3fixer-callable" title="Permalink to this definition">¶</a></dt> <dd><p>Converts <tt class="docutils literal"><span class="pre">callable(x)</span></tt> to <tt class="docutils literal"><span class="pre">isinstance(x,</span> <span class="pre">collections.Callable)</span></tt>, adding an import to <a class="reference internal" href="collections.html#module-collections" title="collections: High-performance datatypes"><tt class="xref py py-mod docutils literal"><span class="pre">collections</span></tt></a> if needed. Note <tt class="docutils literal"><span class="pre">callable(x)</span></tt> has returned in Python 3.2, so if you do not intend to support Python 3.1, you can disable this fixer.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-dict"> <tt class="descname">dict</tt><a class="headerlink" href="#2to3fixer-dict" title="Permalink to this definition">¶</a></dt> <dd><p>Fixes dictionary iteration methods. <a class="reference internal" href="stdtypes.html#dict.iteritems" title="dict.iteritems"><tt class="xref py py-meth docutils literal"><span class="pre">dict.iteritems()</span></tt></a> is converted to <a class="reference internal" href="stdtypes.html#dict.items" title="dict.items"><tt class="xref py py-meth docutils literal"><span class="pre">dict.items()</span></tt></a>, <a class="reference internal" href="stdtypes.html#dict.iterkeys" title="dict.iterkeys"><tt class="xref py py-meth docutils literal"><span class="pre">dict.iterkeys()</span></tt></a> to <a class="reference internal" href="stdtypes.html#dict.keys" title="dict.keys"><tt class="xref py py-meth docutils literal"><span class="pre">dict.keys()</span></tt></a>, and <a class="reference internal" href="stdtypes.html#dict.itervalues" title="dict.itervalues"><tt class="xref py py-meth docutils literal"><span class="pre">dict.itervalues()</span></tt></a> to <a class="reference internal" href="stdtypes.html#dict.values" title="dict.values"><tt class="xref py py-meth docutils literal"><span class="pre">dict.values()</span></tt></a>. Similarly, <a class="reference internal" href="stdtypes.html#dict.viewitems" title="dict.viewitems"><tt class="xref py py-meth docutils literal"><span class="pre">dict.viewitems()</span></tt></a>, <a class="reference internal" href="stdtypes.html#dict.viewkeys" title="dict.viewkeys"><tt class="xref py py-meth docutils literal"><span class="pre">dict.viewkeys()</span></tt></a> and <a class="reference internal" href="stdtypes.html#dict.viewvalues" title="dict.viewvalues"><tt class="xref py py-meth docutils literal"><span class="pre">dict.viewvalues()</span></tt></a> are converted respectively to <a class="reference internal" href="stdtypes.html#dict.items" title="dict.items"><tt class="xref py py-meth docutils literal"><span class="pre">dict.items()</span></tt></a>, <a class="reference internal" href="stdtypes.html#dict.keys" title="dict.keys"><tt class="xref py py-meth docutils literal"><span class="pre">dict.keys()</span></tt></a> and <a class="reference internal" href="stdtypes.html#dict.values" title="dict.values"><tt class="xref py py-meth docutils literal"><span class="pre">dict.values()</span></tt></a>. It also wraps existing usages of <a class="reference internal" href="stdtypes.html#dict.items" title="dict.items"><tt class="xref py py-meth docutils literal"><span class="pre">dict.items()</span></tt></a>, <a class="reference internal" href="stdtypes.html#dict.keys" title="dict.keys"><tt class="xref py py-meth docutils literal"><span class="pre">dict.keys()</span></tt></a>, and <a class="reference internal" href="stdtypes.html#dict.values" title="dict.values"><tt class="xref py py-meth docutils literal"><span class="pre">dict.values()</span></tt></a> in a call to <a class="reference internal" href="functions.html#list" title="list"><tt class="xref py py-class docutils literal"><span class="pre">list</span></tt></a>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-except"> <tt class="descname">except</tt><a class="headerlink" href="#2to3fixer-except" title="Permalink to this definition">¶</a></dt> <dd><p>Converts <tt class="docutils literal"><span class="pre">except</span> <span class="pre">X,</span> <span class="pre">T</span></tt> to <tt class="docutils literal"><span class="pre">except</span> <span class="pre">X</span> <span class="pre">as</span> <span class="pre">T</span></tt>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-exec"> <tt class="descname">exec</tt><a class="headerlink" href="#2to3fixer-exec" title="Permalink to this definition">¶</a></dt> <dd><p>Converts the <a class="reference internal" href="../reference/simple_stmts.html#exec"><tt class="xref std std-keyword docutils literal"><span class="pre">exec</span></tt></a> statement to the <tt class="xref py py-func docutils literal"><span class="pre">exec()</span></tt> function.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-execfile"> <tt class="descname">execfile</tt><a class="headerlink" href="#2to3fixer-execfile" title="Permalink to this definition">¶</a></dt> <dd><p>Removes usage of <a class="reference internal" href="functions.html#execfile" title="execfile"><tt class="xref py py-func docutils literal"><span class="pre">execfile()</span></tt></a>. The argument to <a class="reference internal" href="functions.html#execfile" title="execfile"><tt class="xref py py-func docutils literal"><span class="pre">execfile()</span></tt></a> is wrapped in calls to <a class="reference internal" href="functions.html#open" title="open"><tt class="xref py py-func docutils literal"><span class="pre">open()</span></tt></a>, <a class="reference internal" href="functions.html#compile" title="compile"><tt class="xref py py-func docutils literal"><span class="pre">compile()</span></tt></a>, and <tt class="xref py py-func docutils literal"><span class="pre">exec()</span></tt>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-exitfunc"> <tt class="descname">exitfunc</tt><a class="headerlink" href="#2to3fixer-exitfunc" title="Permalink to this definition">¶</a></dt> <dd><p>Changes assignment of <a class="reference internal" href="sys.html#sys.exitfunc" title="sys.exitfunc"><tt class="xref py py-attr docutils literal"><span class="pre">sys.exitfunc</span></tt></a> to use of the <a class="reference internal" href="atexit.html#module-atexit" title="atexit: Register and execute cleanup functions."><tt class="xref py py-mod docutils literal"><span class="pre">atexit</span></tt></a> module.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-filter"> <tt class="descname">filter</tt><a class="headerlink" href="#2to3fixer-filter" title="Permalink to this definition">¶</a></dt> <dd><p>Wraps <a class="reference internal" href="functions.html#filter" title="filter"><tt class="xref py py-func docutils literal"><span class="pre">filter()</span></tt></a> usage in a <a class="reference internal" href="functions.html#list" title="list"><tt class="xref py py-class docutils literal"><span class="pre">list</span></tt></a> call.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-funcattrs"> <tt class="descname">funcattrs</tt><a class="headerlink" href="#2to3fixer-funcattrs" title="Permalink to this definition">¶</a></dt> <dd><p>Fixes function attributes that have been renamed. For example, <tt class="docutils literal"><span class="pre">my_function.func_closure</span></tt> is converted to <tt class="docutils literal"><span class="pre">my_function.__closure__</span></tt>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-future"> <tt class="descname">future</tt><a class="headerlink" href="#2to3fixer-future" title="Permalink to this definition">¶</a></dt> <dd><p>Removes <tt class="docutils literal"><span class="pre">from</span> <span class="pre">__future__</span> <span class="pre">import</span> <span class="pre">new_feature</span></tt> statements.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-getcwdu"> <tt class="descname">getcwdu</tt><a class="headerlink" href="#2to3fixer-getcwdu" title="Permalink to this definition">¶</a></dt> <dd><p>Renames <a class="reference internal" href="os.html#os.getcwdu" title="os.getcwdu"><tt class="xref py py-func docutils literal"><span class="pre">os.getcwdu()</span></tt></a> to <a class="reference internal" href="os.html#os.getcwd" title="os.getcwd"><tt class="xref py py-func docutils literal"><span class="pre">os.getcwd()</span></tt></a>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-has_key"> <tt class="descname">has_key</tt><a class="headerlink" href="#2to3fixer-has_key" title="Permalink to this definition">¶</a></dt> <dd><p>Changes <tt class="docutils literal"><span class="pre">dict.has_key(key)</span></tt> to <tt class="docutils literal"><span class="pre">key</span> <span class="pre">in</span> <span class="pre">dict</span></tt>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-idioms"> <tt class="descname">idioms</tt><a class="headerlink" href="#2to3fixer-idioms" title="Permalink to this definition">¶</a></dt> <dd><p>This optional fixer performs several transformations that make Python code more idiomatic. Type comparisons like <tt class="docutils literal"><span class="pre">type(x)</span> <span class="pre">is</span> <span class="pre">SomeClass</span></tt> and <tt class="docutils literal"><span class="pre">type(x)</span> <span class="pre">==</span> <span class="pre">SomeClass</span></tt> are converted to <tt class="docutils literal"><span class="pre">isinstance(x,</span> <span class="pre">SomeClass)</span></tt>. <tt class="docutils literal"><span class="pre">while</span> <span class="pre">1</span></tt> becomes <tt class="docutils literal"><span class="pre">while</span> <span class="pre">True</span></tt>. This fixer also tries to make use of <a class="reference internal" href="functions.html#sorted" title="sorted"><tt class="xref py py-func docutils literal"><span class="pre">sorted()</span></tt></a> in appropriate places. For example, this block</p> <div class="highlight-python"><div class="highlight"><pre><span class="n">L</span> <span class="o">=</span> <span class="nb">list</span><span class="p">(</span><span class="n">some_iterable</span><span class="p">)</span> <span class="n">L</span><span class="o">.</span><span class="n">sort</span><span class="p">()</span> </pre></div> </div> <p>is changed to</p> <div class="highlight-python"><div class="highlight"><pre><span class="n">L</span> <span class="o">=</span> <span class="nb">sorted</span><span class="p">(</span><span class="n">some_iterable</span><span class="p">)</span> </pre></div> </div> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-import"> <tt class="descname">import</tt><a class="headerlink" href="#2to3fixer-import" title="Permalink to this definition">¶</a></dt> <dd><p>Detects sibling imports and converts them to relative imports.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-imports"> <tt class="descname">imports</tt><a class="headerlink" href="#2to3fixer-imports" title="Permalink to this definition">¶</a></dt> <dd><p>Handles module renames in the standard library.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-imports2"> <tt class="descname">imports2</tt><a class="headerlink" href="#2to3fixer-imports2" title="Permalink to this definition">¶</a></dt> <dd><p>Handles other modules renames in the standard library. It is separate from the <a class="reference internal" href="#2to3fixer-imports"><tt class="xref std std-2to3fixer docutils literal"><span class="pre">imports</span></tt></a> fixer only because of technical limitations.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-input"> <tt class="descname">input</tt><a class="headerlink" href="#2to3fixer-input" title="Permalink to this definition">¶</a></dt> <dd><p>Converts <tt class="docutils literal"><span class="pre">input(prompt)</span></tt> to <tt class="docutils literal"><span class="pre">eval(input(prompt))</span></tt></p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-intern"> <tt class="descname">intern</tt><a class="headerlink" href="#2to3fixer-intern" title="Permalink to this definition">¶</a></dt> <dd><p>Converts <a class="reference internal" href="functions.html#intern" title="intern"><tt class="xref py py-func docutils literal"><span class="pre">intern()</span></tt></a> to <tt class="xref py py-func docutils literal"><span class="pre">sys.intern()</span></tt>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-isinstance"> <tt class="descname">isinstance</tt><a class="headerlink" href="#2to3fixer-isinstance" title="Permalink to this definition">¶</a></dt> <dd><p>Fixes duplicate types in the second argument of <a class="reference internal" href="functions.html#isinstance" title="isinstance"><tt class="xref py py-func docutils literal"><span class="pre">isinstance()</span></tt></a>. For example, <tt class="docutils literal"><span class="pre">isinstance(x,</span> <span class="pre">(int,</span> <span class="pre">int))</span></tt> is converted to <tt class="docutils literal"><span class="pre">isinstance(x,</span> <span class="pre">(int))</span></tt>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-itertools_imports"> <tt class="descname">itertools_imports</tt><a class="headerlink" href="#2to3fixer-itertools_imports" title="Permalink to this definition">¶</a></dt> <dd><p>Removes imports of <a class="reference internal" href="itertools.html#itertools.ifilter" title="itertools.ifilter"><tt class="xref py py-func docutils literal"><span class="pre">itertools.ifilter()</span></tt></a>, <a class="reference internal" href="itertools.html#itertools.izip" title="itertools.izip"><tt class="xref py py-func docutils literal"><span class="pre">itertools.izip()</span></tt></a>, and <a class="reference internal" href="itertools.html#itertools.imap" title="itertools.imap"><tt class="xref py py-func docutils literal"><span class="pre">itertools.imap()</span></tt></a>. Imports of <a class="reference internal" href="itertools.html#itertools.ifilterfalse" title="itertools.ifilterfalse"><tt class="xref py py-func docutils literal"><span class="pre">itertools.ifilterfalse()</span></tt></a> are also changed to <tt class="xref py py-func docutils literal"><span class="pre">itertools.filterfalse()</span></tt>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-itertools"> <tt class="descname">itertools</tt><a class="headerlink" href="#2to3fixer-itertools" title="Permalink to this definition">¶</a></dt> <dd><p>Changes usage of <a class="reference internal" href="itertools.html#itertools.ifilter" title="itertools.ifilter"><tt class="xref py py-func docutils literal"><span class="pre">itertools.ifilter()</span></tt></a>, <a class="reference internal" href="itertools.html#itertools.izip" title="itertools.izip"><tt class="xref py py-func docutils literal"><span class="pre">itertools.izip()</span></tt></a>, and <a class="reference internal" href="itertools.html#itertools.imap" title="itertools.imap"><tt class="xref py py-func docutils literal"><span class="pre">itertools.imap()</span></tt></a> to their built-in equivalents. <a class="reference internal" href="itertools.html#itertools.ifilterfalse" title="itertools.ifilterfalse"><tt class="xref py py-func docutils literal"><span class="pre">itertools.ifilterfalse()</span></tt></a> is changed to <tt class="xref py py-func docutils literal"><span class="pre">itertools.filterfalse()</span></tt>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-long"> <tt class="descname">long</tt><a class="headerlink" href="#2to3fixer-long" title="Permalink to this definition">¶</a></dt> <dd><p>Renames <a class="reference internal" href="functions.html#long" title="long"><tt class="xref py py-class docutils literal"><span class="pre">long</span></tt></a> to <a class="reference internal" href="functions.html#int" title="int"><tt class="xref py py-class docutils literal"><span class="pre">int</span></tt></a>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-map"> <tt class="descname">map</tt><a class="headerlink" href="#2to3fixer-map" title="Permalink to this definition">¶</a></dt> <dd><p>Wraps <a class="reference internal" href="functions.html#map" title="map"><tt class="xref py py-func docutils literal"><span class="pre">map()</span></tt></a> in a <a class="reference internal" href="functions.html#list" title="list"><tt class="xref py py-class docutils literal"><span class="pre">list</span></tt></a> call. It also changes <tt class="docutils literal"><span class="pre">map(None,</span> <span class="pre">x)</span></tt> to <tt class="docutils literal"><span class="pre">list(x)</span></tt>. Using <tt class="docutils literal"><span class="pre">from</span> <span class="pre">future_builtins</span> <span class="pre">import</span> <span class="pre">map</span></tt> disables this fixer.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-metaclass"> <tt class="descname">metaclass</tt><a class="headerlink" href="#2to3fixer-metaclass" title="Permalink to this definition">¶</a></dt> <dd><p>Converts the old metaclass syntax (<tt class="docutils literal"><span class="pre">__metaclass__</span> <span class="pre">=</span> <span class="pre">Meta</span></tt> in the class body) to the new (<tt class="docutils literal"><span class="pre">class</span> <span class="pre">X(metaclass=Meta)</span></tt>).</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-methodattrs"> <tt class="descname">methodattrs</tt><a class="headerlink" href="#2to3fixer-methodattrs" title="Permalink to this definition">¶</a></dt> <dd><p>Fixes old method attribute names. For example, <tt class="docutils literal"><span class="pre">meth.im_func</span></tt> is converted to <tt class="docutils literal"><span class="pre">meth.__func__</span></tt>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-ne"> <tt class="descname">ne</tt><a class="headerlink" href="#2to3fixer-ne" title="Permalink to this definition">¶</a></dt> <dd><p>Converts the old not-equal syntax, <tt class="docutils literal"><span class="pre"><></span></tt>, to <tt class="docutils literal"><span class="pre">!=</span></tt>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-next"> <tt class="descname">next</tt><a class="headerlink" href="#2to3fixer-next" title="Permalink to this definition">¶</a></dt> <dd><p>Converts the use of iterator’s <a class="reference internal" href="stdtypes.html#iterator.next" title="iterator.next"><tt class="xref py py-meth docutils literal"><span class="pre">next()</span></tt></a> methods to the <a class="reference internal" href="functions.html#next" title="next"><tt class="xref py py-func docutils literal"><span class="pre">next()</span></tt></a> function. It also renames <a class="reference internal" href="functions.html#next" title="next"><tt class="xref py py-meth docutils literal"><span class="pre">next()</span></tt></a> methods to <tt class="xref py py-meth docutils literal"><span class="pre">__next__()</span></tt>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-nonzero"> <tt class="descname">nonzero</tt><a class="headerlink" href="#2to3fixer-nonzero" title="Permalink to this definition">¶</a></dt> <dd><p>Renames <a class="reference internal" href="../reference/datamodel.html#object.__nonzero__" title="object.__nonzero__"><tt class="xref py py-meth docutils literal"><span class="pre">__nonzero__()</span></tt></a> to <tt class="xref py py-meth docutils literal"><span class="pre">__bool__()</span></tt>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-numliterals"> <tt class="descname">numliterals</tt><a class="headerlink" href="#2to3fixer-numliterals" title="Permalink to this definition">¶</a></dt> <dd><p>Converts octal literals into the new syntax.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-paren"> <tt class="descname">paren</tt><a class="headerlink" href="#2to3fixer-paren" title="Permalink to this definition">¶</a></dt> <dd><p>Add extra parenthesis where they are required in list comprehensions. For example, <tt class="docutils literal"><span class="pre">[x</span> <span class="pre">for</span> <span class="pre">x</span> <span class="pre">in</span> <span class="pre">1,</span> <span class="pre">2]</span></tt> becomes <tt class="docutils literal"><span class="pre">[x</span> <span class="pre">for</span> <span class="pre">x</span> <span class="pre">in</span> <span class="pre">(1,</span> <span class="pre">2)]</span></tt>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-print"> <tt class="descname">print</tt><a class="headerlink" href="#2to3fixer-print" title="Permalink to this definition">¶</a></dt> <dd><p>Converts the <a class="reference internal" href="../reference/simple_stmts.html#print"><tt class="xref std std-keyword docutils literal"><span class="pre">print</span></tt></a> statement to the <a class="reference internal" href="functions.html#print" title="print"><tt class="xref py py-func docutils literal"><span class="pre">print()</span></tt></a> function.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-raise"> <tt class="descname">raise</tt><a class="headerlink" href="#2to3fixer-raise" title="Permalink to this definition">¶</a></dt> <dd><p>Converts <tt class="docutils literal"><span class="pre">raise</span> <span class="pre">E,</span> <span class="pre">V</span></tt> to <tt class="docutils literal"><span class="pre">raise</span> <span class="pre">E(V)</span></tt>, and <tt class="docutils literal"><span class="pre">raise</span> <span class="pre">E,</span> <span class="pre">V,</span> <span class="pre">T</span></tt> to <tt class="docutils literal"><span class="pre">raise</span> <span class="pre">E(V).with_traceback(T)</span></tt>. If <tt class="docutils literal"><span class="pre">E</span></tt> is a tuple, the translation will be incorrect because substituting tuples for exceptions has been removed in Python 3.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-raw_input"> <tt class="descname">raw_input</tt><a class="headerlink" href="#2to3fixer-raw_input" title="Permalink to this definition">¶</a></dt> <dd><p>Converts <a class="reference internal" href="functions.html#raw_input" title="raw_input"><tt class="xref py py-func docutils literal"><span class="pre">raw_input()</span></tt></a> to <a class="reference internal" href="functions.html#input" title="input"><tt class="xref py py-func docutils literal"><span class="pre">input()</span></tt></a>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-reduce"> <tt class="descname">reduce</tt><a class="headerlink" href="#2to3fixer-reduce" title="Permalink to this definition">¶</a></dt> <dd><p>Handles the move of <a class="reference internal" href="functions.html#reduce" title="reduce"><tt class="xref py py-func docutils literal"><span class="pre">reduce()</span></tt></a> to <a class="reference internal" href="functools.html#functools.reduce" title="functools.reduce"><tt class="xref py py-func docutils literal"><span class="pre">functools.reduce()</span></tt></a>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-renames"> <tt class="descname">renames</tt><a class="headerlink" href="#2to3fixer-renames" title="Permalink to this definition">¶</a></dt> <dd><p>Changes <a class="reference internal" href="sys.html#sys.maxint" title="sys.maxint"><tt class="xref py py-data docutils literal"><span class="pre">sys.maxint</span></tt></a> to <a class="reference internal" href="sys.html#sys.maxsize" title="sys.maxsize"><tt class="xref py py-data docutils literal"><span class="pre">sys.maxsize</span></tt></a>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-repr"> <tt class="descname">repr</tt><a class="headerlink" href="#2to3fixer-repr" title="Permalink to this definition">¶</a></dt> <dd><p>Replaces backtick repr with the <a class="reference internal" href="repr.html#module-repr" title="repr: Alternate repr() implementation with size limits."><tt class="xref py py-func docutils literal"><span class="pre">repr()</span></tt></a> function.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-set_literal"> <tt class="descname">set_literal</tt><a class="headerlink" href="#2to3fixer-set_literal" title="Permalink to this definition">¶</a></dt> <dd><p>Replaces use of the <a class="reference internal" href="stdtypes.html#set" title="set"><tt class="xref py py-class docutils literal"><span class="pre">set</span></tt></a> constructor with set literals. This fixer is optional.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-standard_error"> <tt class="descname">standard_error</tt><a class="headerlink" href="#2to3fixer-standard_error" title="Permalink to this definition">¶</a></dt> <dd><p>Renames <a class="reference internal" href="exceptions.html#exceptions.StandardError" title="exceptions.StandardError"><tt class="xref py py-exc docutils literal"><span class="pre">StandardError</span></tt></a> to <a class="reference internal" href="exceptions.html#exceptions.Exception" title="exceptions.Exception"><tt class="xref py py-exc docutils literal"><span class="pre">Exception</span></tt></a>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-sys_exc"> <tt class="descname">sys_exc</tt><a class="headerlink" href="#2to3fixer-sys_exc" title="Permalink to this definition">¶</a></dt> <dd><p>Changes the deprecated <a class="reference internal" href="sys.html#sys.exc_value" title="sys.exc_value"><tt class="xref py py-data docutils literal"><span class="pre">sys.exc_value</span></tt></a>, <a class="reference internal" href="sys.html#sys.exc_type" title="sys.exc_type"><tt class="xref py py-data docutils literal"><span class="pre">sys.exc_type</span></tt></a>, <a class="reference internal" href="sys.html#sys.exc_traceback" title="sys.exc_traceback"><tt class="xref py py-data docutils literal"><span class="pre">sys.exc_traceback</span></tt></a> to use <a class="reference internal" href="sys.html#sys.exc_info" title="sys.exc_info"><tt class="xref py py-func docutils literal"><span class="pre">sys.exc_info()</span></tt></a>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-throw"> <tt class="descname">throw</tt><a class="headerlink" href="#2to3fixer-throw" title="Permalink to this definition">¶</a></dt> <dd><p>Fixes the API change in generator’s <tt class="xref py py-meth docutils literal"><span class="pre">throw()</span></tt> method.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-tuple_params"> <tt class="descname">tuple_params</tt><a class="headerlink" href="#2to3fixer-tuple_params" title="Permalink to this definition">¶</a></dt> <dd><p>Removes implicit tuple parameter unpacking. This fixer inserts temporary variables.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-types"> <tt class="descname">types</tt><a class="headerlink" href="#2to3fixer-types" title="Permalink to this definition">¶</a></dt> <dd><p>Fixes code broken from the removal of some members in the <a class="reference internal" href="types.html#module-types" title="types: Names for built-in types."><tt class="xref py py-mod docutils literal"><span class="pre">types</span></tt></a> module.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-unicode"> <tt class="descname">unicode</tt><a class="headerlink" href="#2to3fixer-unicode" title="Permalink to this definition">¶</a></dt> <dd><p>Renames <a class="reference internal" href="functions.html#unicode" title="unicode"><tt class="xref py py-class docutils literal"><span class="pre">unicode</span></tt></a> to <a class="reference internal" href="functions.html#str" title="str"><tt class="xref py py-class docutils literal"><span class="pre">str</span></tt></a>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-urllib"> <tt class="descname">urllib</tt><a class="headerlink" href="#2to3fixer-urllib" title="Permalink to this definition">¶</a></dt> <dd><p>Handles the rename of <a class="reference internal" href="urllib.html#module-urllib" title="urllib: Open an arbitrary network resource by URL (requires sockets)."><tt class="xref py py-mod docutils literal"><span class="pre">urllib</span></tt></a> and <a class="reference internal" href="urllib2.html#module-urllib2" title="urllib2: Next generation URL opening library."><tt class="xref py py-mod docutils literal"><span class="pre">urllib2</span></tt></a> to the <a class="reference internal" href="urllib.html#module-urllib" title="urllib: Open an arbitrary network resource by URL (requires sockets)."><tt class="xref py py-mod docutils literal"><span class="pre">urllib</span></tt></a> package.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-ws_comma"> <tt class="descname">ws_comma</tt><a class="headerlink" href="#2to3fixer-ws_comma" title="Permalink to this definition">¶</a></dt> <dd><p>Removes excess whitespace from comma separated items. This fixer is optional.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-xrange"> <tt class="descname">xrange</tt><a class="headerlink" href="#2to3fixer-xrange" title="Permalink to this definition">¶</a></dt> <dd><p>Renames <a class="reference internal" href="functions.html#xrange" title="xrange"><tt class="xref py py-func docutils literal"><span class="pre">xrange()</span></tt></a> to <a class="reference internal" href="functions.html#range" title="range"><tt class="xref py py-func docutils literal"><span class="pre">range()</span></tt></a> and wraps existing <a class="reference internal" href="functions.html#range" title="range"><tt class="xref py py-func docutils literal"><span class="pre">range()</span></tt></a> calls with <a class="reference internal" href="functions.html#list" title="list"><tt class="xref py py-class docutils literal"><span class="pre">list</span></tt></a>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-xreadlines"> <tt class="descname">xreadlines</tt><a class="headerlink" href="#2to3fixer-xreadlines" title="Permalink to this definition">¶</a></dt> <dd><p>Changes <tt class="docutils literal"><span class="pre">for</span> <span class="pre">x</span> <span class="pre">in</span> <span class="pre">file.xreadlines()</span></tt> to <tt class="docutils literal"><span class="pre">for</span> <span class="pre">x</span> <span class="pre">in</span> <span class="pre">file</span></tt>.</p> </dd></dl> <dl class="2to3fixer"> <dt id="2to3fixer-zip"> <tt class="descname">zip</tt><a class="headerlink" href="#2to3fixer-zip" title="Permalink to this definition">¶</a></dt> <dd><p>Wraps <a class="reference internal" href="functions.html#zip" title="zip"><tt class="xref py py-func docutils literal"><span class="pre">zip()</span></tt></a> usage in a <a class="reference internal" href="functions.html#list" title="list"><tt class="xref py py-class docutils literal"><span class="pre">list</span></tt></a> call. This is disabled when <tt class="docutils literal"><span class="pre">from</span> <span class="pre">future_builtins</span> <span class="pre">import</span> <span class="pre">zip</span></tt> appears.</p> </dd></dl> </div> <div class="section" id="module-lib2to3"> <span id="lib2to3-2to3-s-library"></span><h2>25.4.3. <a class="reference internal" href="#module-lib2to3" title="lib2to3: the 2to3 library"><tt class="xref py py-mod docutils literal"><span class="pre">lib2to3</span></tt></a> - 2to3’s library<a class="headerlink" href="#module-lib2to3" title="Permalink to this headline">¶</a></h2> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The <a class="reference internal" href="#module-lib2to3" title="lib2to3: the 2to3 library"><tt class="xref py py-mod docutils literal"><span class="pre">lib2to3</span></tt></a> API should be considered unstable and may change drastically in the future.</p> </div> </div> </div> </div> </div> </div> <div class="sphinxsidebar"> <div class="sphinxsidebarwrapper"> <h3><a href="../contents.html">Table Of Contents</a></h3> <ul> <li><a class="reference internal" href="#">25.4. 2to3 - Automated Python 2 to 3 code translation</a><ul> <li><a class="reference internal" href="#using-2to3">25.4.1. Using 2to3</a></li> <li><a class="reference internal" href="#fixers">25.4.2. Fixers</a></li> <li><a class="reference internal" href="#module-lib2to3">25.4.3. <tt class="docutils literal"><span class="pre">lib2to3</span></tt> - 2to3’s library</a></li> </ul> </li> </ul> <h4>Previous topic</h4> <p class="topless"><a href="unittest.html" title="previous chapter">25.3. <tt class="docutils literal"><span class="pre">unittest</span></tt> — Unit testing framework</a></p> <h4>Next topic</h4> <p class="topless"><a href="test.html" title="next chapter">25.5. <tt class="docutils literal"><span class="pre">test</span></tt> — Regression tests package for Python</a></p> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../bugs.html">Report a Bug</a></li> <li><a href="../_sources/library/2to3.txt" rel="nofollow">Show Source</a></li> </ul> <div id="searchbox" style="display: none"> <h3>Quick search</h3> <form class="search" action="../search.html" method="get"> <input type="text" name="q" /> <input type="submit" value="Go" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> <p class="searchtip" style="font-size: 90%"> Enter search terms or a module, class or function name. </p> </div> <script type="text/javascript">$('#searchbox').show(0);</script> </div> </div> <div class="clearer"></div> </div> <div class="related"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" >index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="test.html" title="25.5. test — Regression tests package for Python" >next</a> |</li> <li class="right" > <a href="unittest.html" title="25.3. unittest — Unit testing framework" >previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="http://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.5 documentation</a> » </li> <li><a href="index.html" >The Python Standard Library</a> »</li> <li><a href="development.html" >25. 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