0x1949 Team - FAZEMRX - MANAGER

Edit File: functools.html

<!DOCTYPE html>

<title>9.8. functools — Higher-order functions and operations on callable objects &#8212; Python 2.7.18 documentation</title>
 <link rel="stylesheet" type="text/css" href="../_static/pygments.css" />
 <link rel="stylesheet" type="text/css" href="../_static/classic.css" />
 
 <script data-url_root="../" id="documentation_options" src="../_static/documentation_options.js"></script>
 <script src="../_static/jquery.js"></script>
 <script src="../_static/underscore.js"></script>
 <script src="../_static/doctools.js"></script>
 
 <script src="../_static/sidebar.js"></script>
 
 <link rel="search" type="application/opensearchdescription+xml"
 title="Search within Python 2.7.18 documentation"
 href="../_static/opensearch.xml"/>
 <link rel="author" title="About these documents" href="../about.html" />
 <link rel="index" title="Index" href="../genindex.html" />
 <link rel="search" title="Search" href="../search.html" />
 <link rel="copyright" title="Copyright" href="../copyright.html" />
 <link rel="next" title="9.9. operator — Standard operators as functions" href="operator.html" />
 <link rel="prev" title="9.7. itertools — Functions creating iterators for efficient looping" href="itertools.html" />
 <link rel="shortcut icon" type="image/png" href="../_static/py.png" />
 <link rel="canonical" href="file:///usr/share/doc/python2.7/html/library/functools.html" />
 <script type="text/javascript" src="../_static/copybutton.js"></script>

</head><body>
<div id="outdated-warning" style="padding: .5em; text-align: center; background-color: #FFBABA; color: #6A0E0E;">
 This document is for an old version of Python that is <a href="https://devguide.python.org/devcycle/#end-of-life-branches">no longer supported</a>.
 You should install the python3 and python3-doc packages and read the 
 <a href="file:///usr/share/doc/python3-doc/html/library/functools.html"> Python documentation for the Python3 version packaged in this release</a>.
</div>
 
 <div class="related" role="navigation" aria-label="related navigation">
 <h3>Navigation</h3>
 <ul>
 <li class="right" style="margin-right: 10px">
 <a href="../genindex.html" title="General Index"
 accesskey="I">index</a></li>
 <li class="right" >
 <a href="../py-modindex.html" title="Python Module Index"
 >modules</a> |</li>
 <li class="right" >
 <a href="operator.html" title="9.9. operator — Standard operators as functions"
 accesskey="N">next</a> |</li>
 <li class="right" >
 <a href="itertools.html" title="9.7. itertools — Functions creating iterators for efficient looping"
 accesskey="P">previous</a> |</li>
 <li><img src="../_static/py.png" alt=""
 style="vertical-align: middle; margin-top: -1px"/></li>
 <li><a href="https://www.python.org/">Python</a> &#187;</li>
 <li>
 <a href="../index.html">Python 2.7.18 documentation</a> &#187;
 </li>

<li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> &#187;</li>
 <li class="nav-item nav-item-2"><a href="numeric.html" accesskey="U">9. Numeric and Mathematical Modules</a> &#187;</li>
 <li class="nav-item nav-item-this"><a href="">9.8. <code class="xref py py-mod docutils literal notranslate">functools</code> — Higher-order functions and operations on callable objects</a></li> 
 </ul>
 </div>

<div class="document">
 <div class="documentwrapper">
 <div class="bodywrapper">
 <div class="body" role="main">
 
 <section id="module-functools">
<h1>9.8. <a class="reference internal" href="#module-functools" title="functools: Higher-order functions and operations on callable objects."><code class="xref py py-mod docutils literal notranslate">functools</code></a> — Higher-order functions and operations on callable objects<a class="headerlink" href="#module-functools" title="Permalink to this headline">¶</a></h1>
<div class="versionadded">
New in version 2.5.
</div>
Source code: <a class="reference external" href="https://github.com/python/cpython/tree/2.7/Lib/functools.py">Lib/functools.py</a>
<hr class="docutils" />
The <a class="reference internal" href="#module-functools" title="functools: Higher-order functions and operations on callable objects."><code class="xref py py-mod docutils literal notranslate">functools</code></a> module is for higher-order functions: functions that act on
or return other functions. In general, any callable object can be treated as a
function for the purposes of this module.
The <a class="reference internal" href="#module-functools" title="functools: Higher-order functions and operations on callable objects."><code class="xref py py-mod docutils literal notranslate">functools</code></a> module defines the following functions:
<dl class="py function">
<dt class="sig sig-object py" id="functools.cmp_to_key">
functools.cmp_to_key(func)<a class="headerlink" href="#functools.cmp_to_key" title="Permalink to this definition">¶</a></dt>
<dd>Transform an old-style comparison function to a <a class="reference internal" href="../glossary.html#term-key-function">key function</a>. Used
with tools that accept key functions (such as <a class="reference internal" href="functions.html#sorted" title="sorted"><code class="xref py py-func docutils literal notranslate">sorted()</code></a>, <a class="reference internal" href="functions.html#min" title="min"><code class="xref py py-func docutils literal notranslate">min()</code></a>,
<a class="reference internal" href="functions.html#max" title="max"><code class="xref py py-func docutils literal notranslate">max()</code></a>, <a class="reference internal" href="heapq.html#heapq.nlargest" title="heapq.nlargest"><code class="xref py py-func docutils literal notranslate">heapq.nlargest()</code></a>, <a class="reference internal" href="heapq.html#heapq.nsmallest" title="heapq.nsmallest"><code class="xref py py-func docutils literal notranslate">heapq.nsmallest()</code></a>,
<a class="reference internal" href="itertools.html#itertools.groupby" title="itertools.groupby"><code class="xref py py-func docutils literal notranslate">itertools.groupby()</code></a>). This function is primarily used as a transition
tool for programs being converted to Python 3 where comparison functions are
no longer supported.
A comparison function is any callable that accept two arguments, compares them,
and returns a negative number for less-than, zero for equality, or a positive
number for greater-than. A key function is a callable that accepts one
argument and returns another value to be used as the sort key.
Example:
<div class="highlight-default notranslate"><div class="highlight"><pre>sorted(iterable, key=cmp_to_key(locale.strcoll)) # locale-aware sort order
</pre></div>
</div>
For sorting examples and a brief sorting tutorial, see <a class="reference internal" href="../howto/sorting.html#sortinghowto">Sorting HOW TO</a>.
<div class="versionadded">
New in version 2.7.
</div>
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="functools.total_ordering">
functools.total_ordering(cls)<a class="headerlink" href="#functools.total_ordering" title="Permalink to this definition">¶</a></dt>
<dd>Given a class defining one or more rich comparison ordering methods, this
class decorator supplies the rest. This simplifies the effort involved
in specifying all of the possible rich comparison operations:
The class must define one of <code class="xref py py-meth docutils literal notranslate">__lt__()</code>, <code class="xref py py-meth docutils literal notranslate">__le__()</code>,
<code class="xref py py-meth docutils literal notranslate">__gt__()</code>, or <code class="xref py py-meth docutils literal notranslate">__ge__()</code>.
In addition, the class should supply an <code class="xref py py-meth docutils literal notranslate">__eq__()</code> method.
For example:
<div class="highlight-default notranslate"><div class="highlight"><pre>@total_ordering
class Student:
 def __eq__(self, other):
 return ((self.lastname.lower(), self.firstname.lower()) ==
 (other.lastname.lower(), other.firstname.lower()))
 def __lt__(self, other):
 return ((self.lastname.lower(), self.firstname.lower()) &lt;
 (other.lastname.lower(), other.firstname.lower()))
</pre></div>
</div>
<div class="versionadded">
New in version 2.7.
</div>
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="functools.reduce">
functools.reduce(function, iterable[, initializer])<a class="headerlink" href="#functools.reduce" title="Permalink to this definition">¶</a></dt>
<dd>This is the same function as <a class="reference internal" href="functions.html#reduce" title="reduce"><code class="xref py py-func docutils literal notranslate">reduce()</code></a>. It is made available in this module
to allow writing code more forward-compatible with Python 3.
<div class="versionadded">
New in version 2.6.
</div>
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="functools.partial">
functools.partial(func[,*args][, **keywords])<a class="headerlink" href="#functools.partial" title="Permalink to this definition">¶</a></dt>
<dd>Return a new <a class="reference internal" href="#partial-objects">partial object</a> which when called will behave
like func called with the positional arguments args and keyword arguments keywords.
If more arguments are supplied to the call, they are appended to args. If
additional keyword arguments are supplied, they extend and override keywords.
Roughly equivalent to:
<div class="highlight-default notranslate"><div class="highlight"><pre>def partial(func, *args, **keywords):
 def newfunc(*fargs, **fkeywords):
 newkeywords = keywords.copy()
 newkeywords.update(fkeywords)
 return func(*(args + fargs), **newkeywords)
 newfunc.func = func
 newfunc.args = args
 newfunc.keywords = keywords
 return newfunc
</pre></div>
</div>
The <a class="reference internal" href="#functools.partial" title="functools.partial"><code class="xref py py-func docutils literal notranslate">partial()</code></a> is used for partial function application which “freezes”
some portion of a function’s arguments and/or keywords resulting in a new object
with a simplified signature. For example, <a class="reference internal" href="#functools.partial" title="functools.partial"><code class="xref py py-func docutils literal notranslate">partial()</code></a> can be used to create
a callable that behaves like the <a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-func docutils literal notranslate">int()</code></a> function where the base argument
defaults to two:
<div class="doctest highlight-default notranslate"><div class="highlight"><pre>&gt;&gt;&gt; from functools import partial
&gt;&gt;&gt; basetwo = partial(int, base=2)
&gt;&gt;&gt; basetwo.__doc__ = &#39;Convert base 2 string to an int.&#39;
&gt;&gt;&gt; basetwo(&#39;10010&#39;)
18
</pre></div>
</div>
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="functools.update_wrapper">
functools.update_wrapper(wrapper, wrapped[, assigned][, updated])<a class="headerlink" href="#functools.update_wrapper" title="Permalink to this definition">¶</a></dt>
<dd>Update a wrapper function to look like the wrapped function. The optional
arguments are tuples to specify which attributes of the original function are
assigned directly to the matching attributes on the wrapper function and which
attributes of the wrapper function are updated with the corresponding attributes
from the original function. The default values for these arguments are the
module level constants WRAPPER_ASSIGNMENTS (which assigns to the wrapper
function’s __name__, __module__ and __doc__, the documentation string) and
WRAPPER_UPDATES (which updates the wrapper function’s __dict__, i.e. the
instance dictionary).
The main intended use for this function is in <a class="reference internal" href="../glossary.html#term-decorator">decorator</a> functions which
wrap the decorated function and return the wrapper. If the wrapper function is
not updated, the metadata of the returned function will reflect the wrapper
definition rather than the original function definition, which is typically less
than helpful.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="functools.wraps">
functools.wraps(wrapped[, assigned][, updated])<a class="headerlink" href="#functools.wraps" title="Permalink to this definition">¶</a></dt>
<dd>This is a convenience function for invoking <a class="reference internal" href="#functools.update_wrapper" title="functools.update_wrapper"><code class="xref py py-func docutils literal notranslate">update_wrapper()</code></a> as a
function decorator when defining a wrapper function. It is equivalent to
<code class="docutils literal notranslate">partial(update_wrapper, wrapped=wrapped, assigned=assigned, updated=updated)</code>.
For example:
<div class="highlight-default notranslate"><div class="highlight"><pre>&gt;&gt;&gt; from functools import wraps
&gt;&gt;&gt; def my_decorator(f):
... @wraps(f)
... def wrapper(*args, **kwds):
... print &#39;Calling decorated function&#39;
... return f(*args, **kwds)
... return wrapper
...
&gt;&gt;&gt; @my_decorator
... def example():
... &quot;&quot;&quot;Docstring&quot;&quot;&quot;
... print &#39;Called example function&#39;
...
&gt;&gt;&gt; example()
Calling decorated function
Called example function
&gt;&gt;&gt; example.__name__
&#39;example&#39;
&gt;&gt;&gt; example.__doc__
&#39;Docstring&#39;
</pre></div>
</div>
Without the use of this decorator factory, the name of the example function
would have been <code class="docutils literal notranslate">'wrapper'</code>, and the docstring of the original <code class="xref py py-func docutils literal notranslate">example()</code>
would have been lost.
</dd></dl>

<section id="partial-objects">
<h2>9.8.1. <a class="reference internal" href="#functools.partial" title="functools.partial"><code class="xref py py-class docutils literal notranslate">partial</code></a> Objects<a class="headerlink" href="#partial-objects" title="Permalink to this headline">¶</a></h2>
<a class="reference internal" href="#functools.partial" title="functools.partial"><code class="xref py py-class docutils literal notranslate">partial</code></a> objects are callable objects created by <a class="reference internal" href="#functools.partial" title="functools.partial"><code class="xref py py-func docutils literal notranslate">partial()</code></a>. They
have three read-only attributes:
<dl class="py attribute">
<dt class="sig sig-object py" id="functools.partial.func">
partial.func<a class="headerlink" href="#functools.partial.func" title="Permalink to this definition">¶</a></dt>
<dd>A callable object or function. Calls to the <a class="reference internal" href="#functools.partial" title="functools.partial"><code class="xref py py-class docutils literal notranslate">partial</code></a> object will be
forwarded to <a class="reference internal" href="#functools.partial.func" title="functools.partial.func"><code class="xref py py-attr docutils literal notranslate">func</code></a> with new arguments and keywords.
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="functools.partial.args">
partial.args<a class="headerlink" href="#functools.partial.args" title="Permalink to this definition">¶</a></dt>
<dd>The leftmost positional arguments that will be prepended to the positional
arguments provided to a <a class="reference internal" href="#functools.partial" title="functools.partial"><code class="xref py py-class docutils literal notranslate">partial</code></a> object call.
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="functools.partial.keywords">
partial.keywords<a class="headerlink" href="#functools.partial.keywords" title="Permalink to this definition">¶</a></dt>
<dd>The keyword arguments that will be supplied when the <a class="reference internal" href="#functools.partial" title="functools.partial"><code class="xref py py-class docutils literal notranslate">partial</code></a> object is
called.
</dd></dl>

<a class="reference internal" href="#functools.partial" title="functools.partial"><code class="xref py py-class docutils literal notranslate">partial</code></a> objects are like <code class="xref py py-class docutils literal notranslate">function</code> objects in that they are
callable, weak referencable, and can have attributes. There are some important
differences. For instance, the <a class="reference internal" href="stdtypes.html#definition.__name__" title="definition.__name__"><code class="xref py py-attr docutils literal notranslate">__name__</code></a> and <code class="xref py py-attr docutils literal notranslate">__doc__</code> attributes
are not created automatically. Also, <a class="reference internal" href="#functools.partial" title="functools.partial"><code class="xref py py-class docutils literal notranslate">partial</code></a> objects defined in
classes behave like static methods and do not transform into bound methods
during instance attribute look-up.
</section>
</section>

<div class="clearer"></div>
 </div>
 </div>
 </div>
 <div class="sphinxsidebar" role="navigation" aria-label="main navigation">
 <div class="sphinxsidebarwrapper">
 <h3><a href="../contents.html">Table of Contents</a></h3>
 <ul>
<li><a class="reference internal" href="#">9.8. <code class="xref py py-mod docutils literal notranslate">functools</code> — Higher-order functions and operations on callable objects</a><ul>
<li><a class="reference internal" href="#partial-objects">9.8.1. <code class="xref py py-class docutils literal notranslate">partial</code> Objects</a></li>
</ul>
</li>
</ul>

<h4>Previous topic</h4>
 <a href="itertools.html"
 title="previous chapter">9.7. <code class="xref py py-mod docutils literal notranslate">itertools</code> — Functions creating iterators for efficient looping</a>
 <h4>Next topic</h4>
 <a href="operator.html"
 title="next chapter">9.9. <code class="xref py py-mod docutils literal notranslate">operator</code> — Standard operators as functions</a>
 <div role="note" aria-label="source link">
 <h3>This Page</h3>
 <ul class="this-page-menu">
 <li><a href="../_sources/library/functools.rst.txt"
 rel="nofollow">Show Source</a></li>
 </ul>
 </div>
<div id="searchbox" style="display: none" role="search">
 <h3 id="searchlabel">Quick search</h3>
 <div class="searchformwrapper">
 <form class="search" action="../search.html" method="get">
 <input type="text" name="q" aria-labelledby="searchlabel" autocomplete="off" autocorrect="off" autocapitalize="off" spellcheck="false"/>
 <input type="submit" value="Go" />
 </form>
 </div>
</div>
<script>$('#searchbox').show(0);</script>
 </div>
 </div>
 <div class="clearer"></div>
 </div> 
 <div class="related" role="navigation" aria-label="related navigation">
 <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="operator.html" title="9.9. operator — Standard operators as functions"
 >next</a> |</li>
 <li class="right" >
 <a href="itertools.html" title="9.7. itertools — Functions creating iterators for efficient looping"
 >previous</a> |</li>
 <li><img src="../_static/py.png" alt=""
 style="vertical-align: middle; margin-top: -1px"/></li>
 <li><a href="https://www.python.org/">Python</a> &#187;</li>
 <li>
 <a href="../index.html">Python 2.7.18 documentation</a> &#187;
 </li>

<li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> &#187;</li>
 <li class="nav-item nav-item-2"><a href="numeric.html" >9. Numeric and Mathematical Modules</a> &#187;</li>
 <li class="nav-item nav-item-this"><a href="">9.8. <code class="xref py py-mod docutils literal notranslate">functools</code> — Higher-order functions and operations on callable objects</a></li> 
 </ul>
 </div> 
 <div class="footer">
 &copy; <a href="../copyright.html">Copyright</a> 1990-2024, Python Software Foundation.
 
 The Python Software Foundation is a non-profit corporation.
 <a href="https://www.python.org/psf/donations/">Please donate.</a>
 
 Last updated on November 21, 2024.
 <a href="../bugs.html">Found a bug</a>?
 
 Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 4.3.2.
 </div>

</body>
</html>