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 <section id="to3-automated-python-2-to-3-code-translation">
<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>
2to3 is a Python program that reads Python 2.x source code and applies a series
of fixers 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"><code class="xref py py-mod docutils literal notranslate">lib2to3</code></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"><code class="xref py py-mod docutils literal notranslate">lib2to3</code></a> could also be
adapted to custom applications in which Python code needs to be edited
automatically.
<section id="using-2to3">
<h2>25.4.1. Using 2to3<a class="headerlink" href="#using-2to3" title="Permalink to this headline">¶</a></h2>
2to3 will usually be installed with the Python interpreter as a script. It is
also located in the <code class="file docutils literal notranslate">Tools/scripts</code> directory of the Python root.
2to3’s basic arguments are a list of files or directories to transform. The
directories are recursively traversed for Python sources.
Here is a sample Python 2.x source file, <code class="file docutils literal notranslate">example.py</code>:
<div class="highlight-default notranslate"><div class="highlight"><pre>def greet(name):
 print &quot;Hello, {0}!&quot;.format(name)
print &quot;What&#39;s your name?&quot;
name = raw_input()
greet(name)
</pre></div>
</div>
It can be converted to Python 3.x code via 2to3 on the command line:
<div class="highlight-shell-session notranslate"><div class="highlight"><pre>$ 2to3 example.py
</pre></div>
</div>
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 <code class="xref std std-option docutils literal notranslate">-n</code> is also given.) Writing the changes back is
enabled with the <code class="xref std std-option docutils literal notranslate">-w</code> flag:
<div class="highlight-shell-session notranslate"><div class="highlight"><pre>$ 2to3 -w example.py
</pre></div>
</div>
After transformation, <code class="file docutils literal notranslate">example.py</code> looks like this:
<div class="highlight-default notranslate"><div class="highlight"><pre>def greet(name):
 print(&quot;Hello, {0}!&quot;.format(name))
print(&quot;What&#39;s your name?&quot;)
name = input()
greet(name)
</pre></div>
</div>
Comments and exact indentation are preserved throughout the translation process.
By default, 2to3 runs a set of <a class="reference internal" href="#to3-fixers">predefined fixers</a>. The
<code class="xref std std-option docutils literal notranslate">-l</code> flag lists all available fixers. An explicit set of fixers to run
can be given with <code class="xref std std-option docutils literal notranslate">-f</code>. Likewise the <code class="xref std std-option docutils literal notranslate">-x</code> explicitly disables a
fixer. The following example runs only the <code class="docutils literal notranslate">imports</code> and <code class="docutils literal notranslate">has_key</code> fixers:
<div class="highlight-shell-session notranslate"><div class="highlight"><pre>$ 2to3 -f imports -f has_key example.py
</pre></div>
</div>
This command runs every fixer except the <code class="docutils literal notranslate">apply</code> fixer:
<div class="highlight-shell-session notranslate"><div class="highlight"><pre>$ 2to3 -x apply example.py
</pre></div>
</div>
Some fixers are explicit, 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 <code class="docutils literal notranslate">idioms</code> fixer is run:
<div class="highlight-shell-session notranslate"><div class="highlight"><pre>$ 2to3 -f all -f idioms example.py
</pre></div>
</div>
Notice how passing <code class="docutils literal notranslate">all</code> enables all default fixers.
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.
2to3 can also refactor doctests. To enable this mode, use the <code class="xref std std-option docutils literal notranslate">-d</code>
flag. Note that only 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.
The <code class="xref std std-option docutils literal notranslate">-v</code> option enables output of more information on the translation
process.
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 <code class="docutils literal notranslate">from __future__ import print_function</code> compiler directive, it
modifies its internal grammar to interpret <a class="reference internal" href="functions.html#print" title="print"><code class="xref py py-func docutils literal notranslate">print()</code></a> as a function. This
change can also be enabled manually with the <code class="xref std std-option docutils literal notranslate">-p</code> flag. Use
<code class="xref std std-option docutils literal notranslate">-p</code> to run fixers on code that already has had its print statements
converted.
The <code class="xref std std-option docutils literal notranslate">-o</code> or <code class="xref std std-option docutils literal notranslate">--output-dir</code> option allows specification of an
alternate directory for processed output files to be written to. The
<code class="xref std std-option docutils literal notranslate">-n</code> flag is required when using this as backup files do not make sense
when not overwriting the input files.
<div class="versionadded">
New in version 2.7.3: The <code class="xref std std-option docutils literal notranslate">-o</code> option was added.
</div>
The <code class="xref std std-option docutils literal notranslate">-W</code> or <code class="xref std std-option docutils literal notranslate">--write-unchanged-files</code> flag tells 2to3 to always
write output files even if no changes were required to the file. This is most
useful with <code class="xref std std-option docutils literal notranslate">-o</code> so that an entire Python source tree is copied with
translation from one directory to another.
This option implies the <code class="xref std std-option docutils literal notranslate">-w</code> flag as it would not make sense otherwise.
<div class="versionadded">
New in version 2.7.3: The <code class="xref std std-option docutils literal notranslate">-W</code> flag was added.
</div>
The <code class="xref std std-option docutils literal notranslate">--add-suffix</code> option specifies a string to append to all output
filenames. The <code class="xref std std-option docutils literal notranslate">-n</code> flag is required when specifying this as backups
are not necessary when writing to different filenames. Example:
<div class="highlight-shell-session notranslate"><div class="highlight"><pre>$ 2to3 -n -W --add-suffix=3 example.py
</pre></div>
</div>
Will cause a converted file named <code class="docutils literal notranslate">example.py3</code> to be written.
<div class="versionadded">
New in version 2.7.3: The <code class="xref std std-option docutils literal notranslate">--add-suffix</code> option was added.
</div>
To translate an entire project from one directory tree to another use:
<div class="highlight-shell-session notranslate"><div class="highlight"><pre>$ 2to3 --output-dir=python3-version/mycode -W -n python2-version/mycode
</pre></div>
</div>
</section>
<section id="fixers">
<h2>25.4.2. Fixers<a class="headerlink" href="#fixers" title="Permalink to this headline">¶</a></h2>
Each step of transforming code is encapsulated in a fixer. The command <code class="docutils literal notranslate">2to3
-l</code> lists them. As <a class="reference internal" href="#to3-using">documented above</a>, each can be turned on
and off individually. They are described here in more detail.
<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-apply">
apply<a class="headerlink" href="#to3fixer-apply" title="Permalink to this definition">¶</a></dt>
<dd>Removes usage of <a class="reference internal" href="functions.html#apply" title="apply"><code class="xref py py-func docutils literal notranslate">apply()</code></a>. For example <code class="docutils literal notranslate">apply(function, *args,
**kwargs)</code> is converted to <code class="docutils literal notranslate">function(*args, **kwargs)</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-asserts">
asserts<a class="headerlink" href="#to3fixer-asserts" title="Permalink to this definition">¶</a></dt>
<dd>Replaces deprecated <a class="reference internal" href="unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate">unittest</code></a> method names with the correct ones.
<table class="docutils align-default">
<colgroup>
<col style="width: 43%" />
<col style="width: 57%" />
</colgroup>
<thead>
<tr class="row-odd"><th class="head">From</th>
<th class="head">To</th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><code class="docutils literal notranslate">failUnlessEqual(a, b)</code></td>
<td><a class="reference internal" href="unittest.html#unittest.TestCase.assertEqual" title="unittest.TestCase.assertEqual"><code class="xref py py-meth docutils literal notranslate">assertEqual(a, b)</code></a></td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">assertEquals(a, b)</code></td>
<td><a class="reference internal" href="unittest.html#unittest.TestCase.assertEqual" title="unittest.TestCase.assertEqual"><code class="xref py py-meth docutils literal notranslate">assertEqual(a, b)</code></a></td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate">failIfEqual(a, b)</code></td>
<td><a class="reference internal" href="unittest.html#unittest.TestCase.assertNotEqual" title="unittest.TestCase.assertNotEqual"><code class="xref py py-meth docutils literal notranslate">assertNotEqual(a, b)</code></a></td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">assertNotEquals(a, b)</code></td>
<td><a class="reference internal" href="unittest.html#unittest.TestCase.assertNotEqual" title="unittest.TestCase.assertNotEqual"><code class="xref py py-meth docutils literal notranslate">assertNotEqual(a, b)</code></a></td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate">failUnless(a)</code></td>
<td><a class="reference internal" href="unittest.html#unittest.TestCase.assertTrue" title="unittest.TestCase.assertTrue"><code class="xref py py-meth docutils literal notranslate">assertTrue(a)</code></a></td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">assert_(a)</code></td>
<td><a class="reference internal" href="unittest.html#unittest.TestCase.assertTrue" title="unittest.TestCase.assertTrue"><code class="xref py py-meth docutils literal notranslate">assertTrue(a)</code></a></td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate">failIf(a)</code></td>
<td><a class="reference internal" href="unittest.html#unittest.TestCase.assertFalse" title="unittest.TestCase.assertFalse"><code class="xref py py-meth docutils literal notranslate">assertFalse(a)</code></a></td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">failUnlessRaises(exc, cal)</code></td>
<td><a class="reference internal" href="unittest.html#unittest.TestCase.assertRaises" title="unittest.TestCase.assertRaises"><code class="xref py py-meth docutils literal notranslate">assertRaises(exc, cal)</code></a></td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate">failUnlessAlmostEqual(a, b)</code></td>
<td><a class="reference internal" href="unittest.html#unittest.TestCase.assertAlmostEqual" title="unittest.TestCase.assertAlmostEqual"><code class="xref py py-meth docutils literal notranslate">assertAlmostEqual(a, b)</code></a></td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">assertAlmostEquals(a, b)</code></td>
<td><a class="reference internal" href="unittest.html#unittest.TestCase.assertAlmostEqual" title="unittest.TestCase.assertAlmostEqual"><code class="xref py py-meth docutils literal notranslate">assertAlmostEqual(a, b)</code></a></td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate">failIfAlmostEqual(a, b)</code></td>
<td><a class="reference internal" href="unittest.html#unittest.TestCase.assertNotAlmostEqual" title="unittest.TestCase.assertNotAlmostEqual"><code class="xref py py-meth docutils literal notranslate">assertNotAlmostEqual(a, b)</code></a></td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">assertNotAlmostEquals(a, b)</code></td>
<td><a class="reference internal" href="unittest.html#unittest.TestCase.assertNotAlmostEqual" title="unittest.TestCase.assertNotAlmostEqual"><code class="xref py py-meth docutils literal notranslate">assertNotAlmostEqual(a, b)</code></a></td>
</tr>
</tbody>
</table>
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-basestring">
basestring<a class="headerlink" href="#to3fixer-basestring" title="Permalink to this definition">¶</a></dt>
<dd>Converts <a class="reference internal" href="functions.html#basestring" title="basestring"><code class="xref py py-class docutils literal notranslate">basestring</code></a> to <a class="reference internal" href="functions.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-buffer">
buffer<a class="headerlink" href="#to3fixer-buffer" title="Permalink to this definition">¶</a></dt>
<dd>Converts <a class="reference internal" href="functions.html#buffer" title="buffer"><code class="xref py py-class docutils literal notranslate">buffer</code></a> to <a class="reference internal" href="stdtypes.html#memoryview" title="memoryview"><code class="xref py py-class docutils literal notranslate">memoryview</code></a>. This fixer is optional
because the <a class="reference internal" href="stdtypes.html#memoryview" title="memoryview"><code class="xref py py-class docutils literal notranslate">memoryview</code></a> API is similar but not exactly the same as
that of <a class="reference internal" href="functions.html#buffer" title="buffer"><code class="xref py py-class docutils literal notranslate">buffer</code></a>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-dict">
dict<a class="headerlink" href="#to3fixer-dict" title="Permalink to this definition">¶</a></dt>
<dd>Fixes dictionary iteration methods. <a class="reference internal" href="stdtypes.html#dict.iteritems" title="dict.iteritems"><code class="xref py py-meth docutils literal notranslate">dict.iteritems()</code></a> is converted to
<a class="reference internal" href="stdtypes.html#dict.items" title="dict.items"><code class="xref py py-meth docutils literal notranslate">dict.items()</code></a>, <a class="reference internal" href="stdtypes.html#dict.iterkeys" title="dict.iterkeys"><code class="xref py py-meth docutils literal notranslate">dict.iterkeys()</code></a> to <a class="reference internal" href="stdtypes.html#dict.keys" title="dict.keys"><code class="xref py py-meth docutils literal notranslate">dict.keys()</code></a>, and
<a class="reference internal" href="stdtypes.html#dict.itervalues" title="dict.itervalues"><code class="xref py py-meth docutils literal notranslate">dict.itervalues()</code></a> to <a class="reference internal" href="stdtypes.html#dict.values" title="dict.values"><code class="xref py py-meth docutils literal notranslate">dict.values()</code></a>. Similarly,
<a class="reference internal" href="stdtypes.html#dict.viewitems" title="dict.viewitems"><code class="xref py py-meth docutils literal notranslate">dict.viewitems()</code></a>, <a class="reference internal" href="stdtypes.html#dict.viewkeys" title="dict.viewkeys"><code class="xref py py-meth docutils literal notranslate">dict.viewkeys()</code></a> and <a class="reference internal" href="stdtypes.html#dict.viewvalues" title="dict.viewvalues"><code class="xref py py-meth docutils literal notranslate">dict.viewvalues()</code></a> are
converted respectively to <a class="reference internal" href="stdtypes.html#dict.items" title="dict.items"><code class="xref py py-meth docutils literal notranslate">dict.items()</code></a>, <a class="reference internal" href="stdtypes.html#dict.keys" title="dict.keys"><code class="xref py py-meth docutils literal notranslate">dict.keys()</code></a> and
<a class="reference internal" href="stdtypes.html#dict.values" title="dict.values"><code class="xref py py-meth docutils literal notranslate">dict.values()</code></a>. It also wraps existing usages of <a class="reference internal" href="stdtypes.html#dict.items" title="dict.items"><code class="xref py py-meth docutils literal notranslate">dict.items()</code></a>,
<a class="reference internal" href="stdtypes.html#dict.keys" title="dict.keys"><code class="xref py py-meth docutils literal notranslate">dict.keys()</code></a>, and <a class="reference internal" href="stdtypes.html#dict.values" title="dict.values"><code class="xref py py-meth docutils literal notranslate">dict.values()</code></a> in a call to <code class="xref py py-class docutils literal notranslate">list</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-except">
except<a class="headerlink" href="#to3fixer-except" title="Permalink to this definition">¶</a></dt>
<dd>Converts <code class="docutils literal notranslate">except X, T</code> to <code class="docutils literal notranslate">except X as T</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-exec">
exec<a class="headerlink" href="#to3fixer-exec" title="Permalink to this definition">¶</a></dt>
<dd>Converts the <a class="reference internal" href="../reference/simple_stmts.html#exec"><code class="xref std std-keyword docutils literal notranslate">exec</code></a> statement to the <code class="xref py py-func docutils literal notranslate">exec()</code> function.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-execfile">
execfile<a class="headerlink" href="#to3fixer-execfile" title="Permalink to this definition">¶</a></dt>
<dd>Removes usage of <a class="reference internal" href="functions.html#execfile" title="execfile"><code class="xref py py-func docutils literal notranslate">execfile()</code></a>. The argument to <a class="reference internal" href="functions.html#execfile" title="execfile"><code class="xref py py-func docutils literal notranslate">execfile()</code></a> is
wrapped in calls to <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate">open()</code></a>, <a class="reference internal" href="functions.html#compile" title="compile"><code class="xref py py-func docutils literal notranslate">compile()</code></a>, and <code class="xref py py-func docutils literal notranslate">exec()</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-exitfunc">
exitfunc<a class="headerlink" href="#to3fixer-exitfunc" title="Permalink to this definition">¶</a></dt>
<dd>Changes assignment of <a class="reference internal" href="sys.html#sys.exitfunc" title="sys.exitfunc"><code class="xref py py-attr docutils literal notranslate">sys.exitfunc</code></a> to use of the <a class="reference internal" href="atexit.html#module-atexit" title="atexit: Register and execute cleanup functions."><code class="xref py py-mod docutils literal notranslate">atexit</code></a>
module.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-filter">
filter<a class="headerlink" href="#to3fixer-filter" title="Permalink to this definition">¶</a></dt>
<dd>Wraps <a class="reference internal" href="functions.html#filter" title="filter"><code class="xref py py-func docutils literal notranslate">filter()</code></a> usage in a <code class="xref py py-class docutils literal notranslate">list</code> call.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-funcattrs">
funcattrs<a class="headerlink" href="#to3fixer-funcattrs" title="Permalink to this definition">¶</a></dt>
<dd>Fixes function attributes that have been renamed. For example,
<code class="docutils literal notranslate">my_function.func_closure</code> is converted to <code class="docutils literal notranslate">my_function.__closure__</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-future">
future<a class="headerlink" href="#to3fixer-future" title="Permalink to this definition">¶</a></dt>
<dd>Removes <code class="docutils literal notranslate">from __future__ import new_feature</code> statements.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-getcwdu">
getcwdu<a class="headerlink" href="#to3fixer-getcwdu" title="Permalink to this definition">¶</a></dt>
<dd>Renames <a class="reference internal" href="os.html#os.getcwdu" title="os.getcwdu"><code class="xref py py-func docutils literal notranslate">os.getcwdu()</code></a> to <a class="reference internal" href="os.html#os.getcwd" title="os.getcwd"><code class="xref py py-func docutils literal notranslate">os.getcwd()</code></a>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-has_key">
has_key<a class="headerlink" href="#to3fixer-has_key" title="Permalink to this definition">¶</a></dt>
<dd>Changes <code class="docutils literal notranslate">dict.has_key(key)</code> to <code class="docutils literal notranslate">key in dict</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-idioms">
idioms<a class="headerlink" href="#to3fixer-idioms" title="Permalink to this definition">¶</a></dt>
<dd>This optional fixer performs several transformations that make Python code
more idiomatic. Type comparisons like <code class="docutils literal notranslate">type(x) is SomeClass</code> and
<code class="docutils literal notranslate">type(x) == SomeClass</code> are converted to <code class="docutils literal notranslate">isinstance(x, SomeClass)</code>.
<code class="docutils literal notranslate">while 1</code> becomes <code class="docutils literal notranslate">while True</code>. This fixer also tries to make use of
<a class="reference internal" href="functions.html#sorted" title="sorted"><code class="xref py py-func docutils literal notranslate">sorted()</code></a> in appropriate places. For example, this block
<div class="highlight-default notranslate"><div class="highlight"><pre>L = list(some_iterable)
L.sort()
</pre></div>
</div>
is changed to
<div class="highlight-default notranslate"><div class="highlight"><pre>L = sorted(some_iterable)
</pre></div>
</div>
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-import">
import<a class="headerlink" href="#to3fixer-import" title="Permalink to this definition">¶</a></dt>
<dd>Detects sibling imports and converts them to relative imports.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-imports">
imports<a class="headerlink" href="#to3fixer-imports" title="Permalink to this definition">¶</a></dt>
<dd>Handles module renames in the standard library.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-imports2">
imports2<a class="headerlink" href="#to3fixer-imports2" title="Permalink to this definition">¶</a></dt>
<dd>Handles other modules renames in the standard library. It is separate from
the <a class="reference internal" href="#to3fixer-imports"><code class="xref std std-2to3fixer docutils literal notranslate">imports</code></a> fixer only because of technical limitations.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-input">
input<a class="headerlink" href="#to3fixer-input" title="Permalink to this definition">¶</a></dt>
<dd>Converts <code class="docutils literal notranslate">input(prompt)</code> to <code class="docutils literal notranslate">eval(input(prompt))</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-intern">
intern<a class="headerlink" href="#to3fixer-intern" title="Permalink to this definition">¶</a></dt>
<dd>Converts <a class="reference internal" href="functions.html#intern" title="intern"><code class="xref py py-func docutils literal notranslate">intern()</code></a> to <code class="xref py py-func docutils literal notranslate">sys.intern()</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-isinstance">
isinstance<a class="headerlink" href="#to3fixer-isinstance" title="Permalink to this definition">¶</a></dt>
<dd>Fixes duplicate types in the second argument of <a class="reference internal" href="functions.html#isinstance" title="isinstance"><code class="xref py py-func docutils literal notranslate">isinstance()</code></a>. For
example, <code class="docutils literal notranslate">isinstance(x, (int, int))</code> is converted to <code class="docutils literal notranslate">isinstance(x,
(int))</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-itertools_imports">
itertools_imports<a class="headerlink" href="#to3fixer-itertools_imports" title="Permalink to this definition">¶</a></dt>
<dd>Removes imports of <a class="reference internal" href="itertools.html#itertools.ifilter" title="itertools.ifilter"><code class="xref py py-func docutils literal notranslate">itertools.ifilter()</code></a>, <a class="reference internal" href="itertools.html#itertools.izip" title="itertools.izip"><code class="xref py py-func docutils literal notranslate">itertools.izip()</code></a>, and
<a class="reference internal" href="itertools.html#itertools.imap" title="itertools.imap"><code class="xref py py-func docutils literal notranslate">itertools.imap()</code></a>. Imports of <a class="reference internal" href="itertools.html#itertools.ifilterfalse" title="itertools.ifilterfalse"><code class="xref py py-func docutils literal notranslate">itertools.ifilterfalse()</code></a> are also
changed to <code class="xref py py-func docutils literal notranslate">itertools.filterfalse()</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-itertools">
itertools<a class="headerlink" href="#to3fixer-itertools" title="Permalink to this definition">¶</a></dt>
<dd>Changes usage of <a class="reference internal" href="itertools.html#itertools.ifilter" title="itertools.ifilter"><code class="xref py py-func docutils literal notranslate">itertools.ifilter()</code></a>, <a class="reference internal" href="itertools.html#itertools.izip" title="itertools.izip"><code class="xref py py-func docutils literal notranslate">itertools.izip()</code></a>, and
<a class="reference internal" href="itertools.html#itertools.imap" title="itertools.imap"><code class="xref py py-func docutils literal notranslate">itertools.imap()</code></a> to their built-in equivalents.
<a class="reference internal" href="itertools.html#itertools.ifilterfalse" title="itertools.ifilterfalse"><code class="xref py py-func docutils literal notranslate">itertools.ifilterfalse()</code></a> is changed to <code class="xref py py-func docutils literal notranslate">itertools.filterfalse()</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-long">
long<a class="headerlink" href="#to3fixer-long" title="Permalink to this definition">¶</a></dt>
<dd>Renames <a class="reference internal" href="functions.html#long" title="long"><code class="xref py py-class docutils literal notranslate">long</code></a> to <a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-map">
map<a class="headerlink" href="#to3fixer-map" title="Permalink to this definition">¶</a></dt>
<dd>Wraps <a class="reference internal" href="functions.html#map" title="map"><code class="xref py py-func docutils literal notranslate">map()</code></a> in a <code class="xref py py-class docutils literal notranslate">list</code> call. It also changes <code class="docutils literal notranslate">map(None, x)</code>
to <code class="docutils literal notranslate">list(x)</code>. Using <code class="docutils literal notranslate">from future_builtins import map</code> disables this
fixer.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-metaclass">
metaclass<a class="headerlink" href="#to3fixer-metaclass" title="Permalink to this definition">¶</a></dt>
<dd>Converts the old metaclass syntax (<code class="docutils literal notranslate">__metaclass__ = Meta</code> in the class
body) to the new (<code class="docutils literal notranslate">class X(metaclass=Meta)</code>).
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-methodattrs">
methodattrs<a class="headerlink" href="#to3fixer-methodattrs" title="Permalink to this definition">¶</a></dt>
<dd>Fixes old method attribute names. For example, <code class="docutils literal notranslate">meth.im_func</code> is converted
to <code class="docutils literal notranslate">meth.__func__</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-ne">
ne<a class="headerlink" href="#to3fixer-ne" title="Permalink to this definition">¶</a></dt>
<dd>Converts the old not-equal syntax, <code class="docutils literal notranslate">&lt;&gt;</code>, to <code class="docutils literal notranslate">!=</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-next">
next<a class="headerlink" href="#to3fixer-next" title="Permalink to this definition">¶</a></dt>
<dd>Converts the use of iterator’s <a class="reference internal" href="stdtypes.html#iterator.next" title="iterator.next"><code class="xref py py-meth docutils literal notranslate">next()</code></a> methods to the
<a class="reference internal" href="functions.html#next" title="next"><code class="xref py py-func docutils literal notranslate">next()</code></a> function. It also renames <a class="reference internal" href="stdtypes.html#iterator.next" title="iterator.next"><code class="xref py py-meth docutils literal notranslate">next()</code></a> methods to
<code class="xref py py-meth docutils literal notranslate">__next__()</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-nonzero">
nonzero<a class="headerlink" href="#to3fixer-nonzero" title="Permalink to this definition">¶</a></dt>
<dd>Renames <code class="xref py py-meth docutils literal notranslate">__nonzero__()</code> to <code class="xref py py-meth docutils literal notranslate">__bool__()</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-numliterals">
numliterals<a class="headerlink" href="#to3fixer-numliterals" title="Permalink to this definition">¶</a></dt>
<dd>Converts octal literals into the new syntax.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-paren">
paren<a class="headerlink" href="#to3fixer-paren" title="Permalink to this definition">¶</a></dt>
<dd>Add extra parenthesis where they are required in list comprehensions. For
example, <code class="docutils literal notranslate">[x for x in 1, 2]</code> becomes <code class="docutils literal notranslate">[x for x in (1, 2)]</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-print">
print<a class="headerlink" href="#to3fixer-print" title="Permalink to this definition">¶</a></dt>
<dd>Converts the <a class="reference internal" href="../reference/simple_stmts.html#print"><code class="xref std std-keyword docutils literal notranslate">print</code></a> statement to the <a class="reference internal" href="functions.html#print" title="print"><code class="xref py py-func docutils literal notranslate">print()</code></a> function.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-raise">
raise<a class="headerlink" href="#to3fixer-raise" title="Permalink to this definition">¶</a></dt>
<dd>Converts <code class="docutils literal notranslate">raise E, V</code> to <code class="docutils literal notranslate">raise E(V)</code>, and <code class="docutils literal notranslate">raise E, V, T</code> to <code class="docutils literal notranslate">raise
E(V).with_traceback(T)</code>. If <code class="docutils literal notranslate">E</code> is a tuple, the translation will be
incorrect because substituting tuples for exceptions has been removed in Python 3.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-raw_input">
raw_input<a class="headerlink" href="#to3fixer-raw_input" title="Permalink to this definition">¶</a></dt>
<dd>Converts <a class="reference internal" href="functions.html#raw_input" title="raw_input"><code class="xref py py-func docutils literal notranslate">raw_input()</code></a> to <a class="reference internal" href="functions.html#input" title="input"><code class="xref py py-func docutils literal notranslate">input()</code></a>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-reduce">
reduce<a class="headerlink" href="#to3fixer-reduce" title="Permalink to this definition">¶</a></dt>
<dd>Handles the move of <a class="reference internal" href="functions.html#reduce" title="reduce"><code class="xref py py-func docutils literal notranslate">reduce()</code></a> to <a class="reference internal" href="functools.html#functools.reduce" title="functools.reduce"><code class="xref py py-func docutils literal notranslate">functools.reduce()</code></a>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-renames">
renames<a class="headerlink" href="#to3fixer-renames" title="Permalink to this definition">¶</a></dt>
<dd>Changes <a class="reference internal" href="sys.html#sys.maxint" title="sys.maxint"><code class="xref py py-data docutils literal notranslate">sys.maxint</code></a> to <a class="reference internal" href="sys.html#sys.maxsize" title="sys.maxsize"><code class="xref py py-data docutils literal notranslate">sys.maxsize</code></a>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-repr">
repr<a class="headerlink" href="#to3fixer-repr" title="Permalink to this definition">¶</a></dt>
<dd>Replaces backtick repr with the <a class="reference internal" href="functions.html#repr" title="repr"><code class="xref py py-func docutils literal notranslate">repr()</code></a> function.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-set_literal">
set_literal<a class="headerlink" href="#to3fixer-set_literal" title="Permalink to this definition">¶</a></dt>
<dd>Replaces use of the <a class="reference internal" href="stdtypes.html#set" title="set"><code class="xref py py-class docutils literal notranslate">set</code></a> constructor with set literals. This fixer
is optional.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-standarderror">
standarderror<a class="headerlink" href="#to3fixer-standarderror" title="Permalink to this definition">¶</a></dt>
<dd>Renames <code class="xref py py-exc docutils literal notranslate">StandardError</code> to <code class="xref py py-exc docutils literal notranslate">Exception</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-sys_exc">
sys_exc<a class="headerlink" href="#to3fixer-sys_exc" title="Permalink to this definition">¶</a></dt>
<dd>Changes the deprecated <a class="reference internal" href="sys.html#sys.exc_value" title="sys.exc_value"><code class="xref py py-data docutils literal notranslate">sys.exc_value</code></a>, <a class="reference internal" href="sys.html#sys.exc_type" title="sys.exc_type"><code class="xref py py-data docutils literal notranslate">sys.exc_type</code></a>,
<a class="reference internal" href="sys.html#sys.exc_traceback" title="sys.exc_traceback"><code class="xref py py-data docutils literal notranslate">sys.exc_traceback</code></a> to use <a class="reference internal" href="sys.html#sys.exc_info" title="sys.exc_info"><code class="xref py py-func docutils literal notranslate">sys.exc_info()</code></a>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-throw">
throw<a class="headerlink" href="#to3fixer-throw" title="Permalink to this definition">¶</a></dt>
<dd>Fixes the API change in generator’s <code class="xref py py-meth docutils literal notranslate">throw()</code> method.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-tuple_params">
tuple_params<a class="headerlink" href="#to3fixer-tuple_params" title="Permalink to this definition">¶</a></dt>
<dd>Removes implicit tuple parameter unpacking. This fixer inserts temporary
variables.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-types">
types<a class="headerlink" href="#to3fixer-types" title="Permalink to this definition">¶</a></dt>
<dd>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."><code class="xref py py-mod docutils literal notranslate">types</code></a>
module.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-unicode">
unicode<a class="headerlink" href="#to3fixer-unicode" title="Permalink to this definition">¶</a></dt>
<dd>Renames <a class="reference internal" href="functions.html#unicode" title="unicode"><code class="xref py py-class docutils literal notranslate">unicode</code></a> to <a class="reference internal" href="functions.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-urllib">
urllib<a class="headerlink" href="#to3fixer-urllib" title="Permalink to this definition">¶</a></dt>
<dd>Handles the rename of <a class="reference internal" href="urllib.html#module-urllib" title="urllib: Open an arbitrary network resource by URL (requires sockets)."><code class="xref py py-mod docutils literal notranslate">urllib</code></a> and <a class="reference internal" href="urllib2.html#module-urllib2" title="urllib2: Next generation URL opening library."><code class="xref py py-mod docutils literal notranslate">urllib2</code></a> to the <a class="reference internal" href="urllib.html#module-urllib" title="urllib: Open an arbitrary network resource by URL (requires sockets)."><code class="xref py py-mod docutils literal notranslate">urllib</code></a>
package.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-ws_comma">
ws_comma<a class="headerlink" href="#to3fixer-ws_comma" title="Permalink to this definition">¶</a></dt>
<dd>Removes excess whitespace from comma separated items. This fixer is
optional.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-xrange">
xrange<a class="headerlink" href="#to3fixer-xrange" title="Permalink to this definition">¶</a></dt>
<dd>Renames <a class="reference internal" href="functions.html#xrange" title="xrange"><code class="xref py py-func docutils literal notranslate">xrange()</code></a> to <a class="reference internal" href="functions.html#range" title="range"><code class="xref py py-func docutils literal notranslate">range()</code></a> and wraps existing <a class="reference internal" href="functions.html#range" title="range"><code class="xref py py-func docutils literal notranslate">range()</code></a>
calls with <code class="xref py py-class docutils literal notranslate">list</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-xreadlines">
xreadlines<a class="headerlink" href="#to3fixer-xreadlines" title="Permalink to this definition">¶</a></dt>
<dd>Changes <code class="docutils literal notranslate">for x in file.xreadlines()</code> to <code class="docutils literal notranslate">for x in file</code>.
</dd></dl>

<dl class="std 2to3fixer">
<dt class="sig sig-object std" id="to3fixer-zip">
zip<a class="headerlink" href="#to3fixer-zip" title="Permalink to this definition">¶</a></dt>
<dd>Wraps <a class="reference internal" href="functions.html#zip" title="zip"><code class="xref py py-func docutils literal notranslate">zip()</code></a> usage in a <code class="xref py py-class docutils literal notranslate">list</code> call. This is disabled when
<code class="docutils literal notranslate">from future_builtins import zip</code> appears.
</dd></dl>

</section>
<section id="module-lib2to3">
<h2>25.4.3. <a class="reference internal" href="#module-lib2to3" title="lib2to3: the 2to3 library"><code class="xref py py-mod docutils literal notranslate">lib2to3</code></a> - 2to3’s library<a class="headerlink" href="#module-lib2to3" title="Permalink to this headline">¶</a></h2>
<div class="admonition note">
Note
The <a class="reference internal" href="#module-lib2to3" title="lib2to3: the 2to3 library"><code class="xref py py-mod docutils literal notranslate">lib2to3</code></a> API should be considered unstable and may change
drastically in the future.
</div>
</section>
</section>

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<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. <code class="xref py py-mod docutils literal notranslate">lib2to3</code> - 2to3’s library</a></li>
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