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<div class="section" id="module-types">
<span id="types-dynamic-type-creation-and-names-for-built-in-types"></span><h1>8.9. <a class="reference internal" href="#module-types" title="types: Names for built-in types."><tt class="xref py py-mod docutils literal"><span class="pre">types</span></tt></a> — Dynamic type creation and names for built-in types<a class="headerlink" href="#module-types" title="Permalink to this headline">¶</a></h1>
<p><strong>Source code:</strong> <a class="reference external" href="http://hg.python.org/cpython/file/3.3/Lib/types.py">Lib/types.py</a></p>
<hr class="docutils" />
<p>This module defines utility function to assist in dynamic creation of
new types.</p>
<p>It also defines names for some object types that are used by the standard
Python interpreter, but not exposed as builtins like <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> or
<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> are.</p>
<div class="section" id="dynamic-type-creation">
<h2>8.9.1. Dynamic Type Creation<a class="headerlink" href="#dynamic-type-creation" title="Permalink to this headline">¶</a></h2>
<dl class="function">
<dt id="types.new_class">
<tt class="descclassname">types.</tt><tt class="descname">new_class</tt><big>(</big><em>name</em>, <em>bases=()</em>, <em>kwds=None</em>, <em>exec_body=None</em><big>)</big><a class="headerlink" href="#types.new_class" title="Permalink to this definition">¶</a></dt>
<dd><p>Creates a class object dynamically using the appropriate metaclass.</p>
<p>The first three arguments are the components that make up a class
definition header: the class name, the base classes (in order), the
keyword arguments (such as <tt class="docutils literal"><span class="pre">metaclass</span></tt>).</p>
<p>The <em>exec_body</em> argument is a callback that is used to populate the
freshly created class namespace. It should accept the class namespace
as its sole argument and update the namespace directly with the class
contents. If no callback is provided, it has the same effect as passing
in <tt class="docutils literal"><span class="pre">lambda</span> <span class="pre">ns:</span> <span class="pre">ns</span></tt>.</p>
<p class="versionadded">
<span class="versionmodified">New in version 3.3.</span> </p>
</dd></dl>
<dl class="function">
<dt id="types.prepare_class">
<tt class="descclassname">types.</tt><tt class="descname">prepare_class</tt><big>(</big><em>name</em>, <em>bases=()</em>, <em>kwds=None</em><big>)</big><a class="headerlink" href="#types.prepare_class" title="Permalink to this definition">¶</a></dt>
<dd><p>Calculates the appropriate metaclass and creates the class namespace.</p>
<p>The arguments are the components that make up a class definition header:
the class name, the base classes (in order) and the keyword arguments
(such as <tt class="docutils literal"><span class="pre">metaclass</span></tt>).</p>
<p>The return value is a 3-tuple: <tt class="docutils literal"><span class="pre">metaclass,</span> <span class="pre">namespace,</span> <span class="pre">kwds</span></tt></p>
<p><em>metaclass</em> is the appropriate metaclass, <em>namespace</em> is the
prepared class namespace and <em>kwds</em> is an updated copy of the passed
in <em>kwds</em> argument with any <tt class="docutils literal"><span class="pre">'metaclass'</span></tt> entry removed. If no <em>kwds</em>
argument is passed in, this will be an empty dict.</p>
<p class="versionadded">
<span class="versionmodified">New in version 3.3.</span> </p>
</dd></dl>
<div class="admonition-see-also admonition seealso">
<p class="first admonition-title">See also</p>
<dl class="last docutils">
<dt><a class="reference internal" href="../reference/datamodel.html#metaclasses"><em>Customizing class creation</em></a></dt>
<dd>Full details of the class creation process supported by these functions</dd>
<dt><span class="target" id="index-0"></span><a class="pep reference external" href="http://www.python.org/dev/peps/pep-3115"><strong>PEP 3115</strong></a> - Metaclasses in Python 3000</dt>
<dd>Introduced the <tt class="docutils literal"><span class="pre">__prepare__</span></tt> namespace hook</dd>
</dl>
</div>
</div>
<div class="section" id="standard-interpreter-types">
<h2>8.9.2. Standard Interpreter Types<a class="headerlink" href="#standard-interpreter-types" title="Permalink to this headline">¶</a></h2>
<p>This module provides names for many of the types that are required to
implement a Python interpreter. It deliberately avoids including some of
the types that arise only incidentally during processing such as the
<tt class="docutils literal"><span class="pre">listiterator</span></tt> type.</p>
<p>Typical use is of these names is for <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> or
<a class="reference internal" href="functions.html#issubclass" title="issubclass"><tt class="xref py py-func docutils literal"><span class="pre">issubclass()</span></tt></a> checks.</p>
<p>Standard names are defined for the following types:</p>
<dl class="data">
<dt id="types.FunctionType">
<tt class="descclassname">types.</tt><tt class="descname">FunctionType</tt><a class="headerlink" href="#types.FunctionType" title="Permalink to this definition">¶</a></dt>
<dt id="types.LambdaType">
<tt class="descclassname">types.</tt><tt class="descname">LambdaType</tt><a class="headerlink" href="#types.LambdaType" title="Permalink to this definition">¶</a></dt>
<dd><p>The type of user-defined functions and functions created by
<a class="reference internal" href="../reference/expressions.html#lambda"><tt class="xref std std-keyword docutils literal"><span class="pre">lambda</span></tt></a> expressions.</p>
</dd></dl>
<dl class="data">
<dt id="types.GeneratorType">
<tt class="descclassname">types.</tt><tt class="descname">GeneratorType</tt><a class="headerlink" href="#types.GeneratorType" title="Permalink to this definition">¶</a></dt>
<dd><p>The type of <a class="reference internal" href="../glossary.html#term-generator"><em class="xref std std-term">generator</em></a>-iterator objects, produced by calling a
generator function.</p>
</dd></dl>
<dl class="data">
<dt id="types.CodeType">
<tt class="descclassname">types.</tt><tt class="descname">CodeType</tt><a class="headerlink" href="#types.CodeType" title="Permalink to this definition">¶</a></dt>
<dd><p id="index-1">The type for code objects such as returned by <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>.</p>
</dd></dl>
<dl class="data">
<dt id="types.MethodType">
<tt class="descclassname">types.</tt><tt class="descname">MethodType</tt><a class="headerlink" href="#types.MethodType" title="Permalink to this definition">¶</a></dt>
<dd><p>The type of methods of user-defined class instances.</p>
</dd></dl>
<dl class="data">
<dt id="types.BuiltinFunctionType">
<tt class="descclassname">types.</tt><tt class="descname">BuiltinFunctionType</tt><a class="headerlink" href="#types.BuiltinFunctionType" title="Permalink to this definition">¶</a></dt>
<dt id="types.BuiltinMethodType">
<tt class="descclassname">types.</tt><tt class="descname">BuiltinMethodType</tt><a class="headerlink" href="#types.BuiltinMethodType" title="Permalink to this definition">¶</a></dt>
<dd><p>The type of built-in functions like <a class="reference internal" href="functions.html#len" title="len"><tt class="xref py py-func docutils literal"><span class="pre">len()</span></tt></a> or <a class="reference internal" href="sys.html#sys.exit" title="sys.exit"><tt class="xref py py-func docutils literal"><span class="pre">sys.exit()</span></tt></a>, and
methods of built-in classes. (Here, the term “built-in” means “written in
C”.)</p>
</dd></dl>
<dl class="data">
<dt id="types.ModuleType">
<tt class="descclassname">types.</tt><tt class="descname">ModuleType</tt><a class="headerlink" href="#types.ModuleType" title="Permalink to this definition">¶</a></dt>
<dd><p>The type of modules.</p>
</dd></dl>
<dl class="data">
<dt id="types.TracebackType">
<tt class="descclassname">types.</tt><tt class="descname">TracebackType</tt><a class="headerlink" href="#types.TracebackType" title="Permalink to this definition">¶</a></dt>
<dd><p>The type of traceback objects such as found in <tt class="docutils literal"><span class="pre">sys.exc_info()[2]</span></tt>.</p>
</dd></dl>
<dl class="data">
<dt id="types.FrameType">
<tt class="descclassname">types.</tt><tt class="descname">FrameType</tt><a class="headerlink" href="#types.FrameType" title="Permalink to this definition">¶</a></dt>
<dd><p>The type of frame objects such as found in <tt class="docutils literal"><span class="pre">tb.tb_frame</span></tt> if <tt class="docutils literal"><span class="pre">tb</span></tt> is a
traceback object.</p>
</dd></dl>
<dl class="data">
<dt id="types.GetSetDescriptorType">
<tt class="descclassname">types.</tt><tt class="descname">GetSetDescriptorType</tt><a class="headerlink" href="#types.GetSetDescriptorType" title="Permalink to this definition">¶</a></dt>
<dd><p>The type of objects defined in extension modules with <tt class="docutils literal"><span class="pre">PyGetSetDef</span></tt>, such
as <tt class="docutils literal"><span class="pre">FrameType.f_locals</span></tt> or <tt class="docutils literal"><span class="pre">array.array.typecode</span></tt>. This type is used as
descriptor for object attributes; it has the same purpose as the
<a class="reference internal" href="functions.html#property" title="property"><tt class="xref py py-class docutils literal"><span class="pre">property</span></tt></a> type, but for classes defined in extension modules.</p>
</dd></dl>
<dl class="data">
<dt id="types.MemberDescriptorType">
<tt class="descclassname">types.</tt><tt class="descname">MemberDescriptorType</tt><a class="headerlink" href="#types.MemberDescriptorType" title="Permalink to this definition">¶</a></dt>
<dd><p>The type of objects defined in extension modules with <tt class="docutils literal"><span class="pre">PyMemberDef</span></tt>, such
as <tt class="docutils literal"><span class="pre">datetime.timedelta.days</span></tt>. This type is used as descriptor for simple C
data members which use standard conversion functions; it has the same purpose
as the <a class="reference internal" href="functions.html#property" title="property"><tt class="xref py py-class docutils literal"><span class="pre">property</span></tt></a> type, but for classes defined in extension modules.</p>
<div class="impl-detail compound">
<p><strong>CPython implementation detail:</strong> In other implementations of Python, this type may be identical to
<tt class="docutils literal"><span class="pre">GetSetDescriptorType</span></tt>.</p>
</div>
</dd></dl>
<dl class="class">
<dt id="types.MappingProxyType">
<em class="property">class </em><tt class="descclassname">types.</tt><tt class="descname">MappingProxyType</tt><big>(</big><em>mapping</em><big>)</big><a class="headerlink" href="#types.MappingProxyType" title="Permalink to this definition">¶</a></dt>
<dd><p>Read-only proxy of a mapping. It provides a dynamic view on the mapping’s
entries, which means that when the mapping changes, the view reflects these
changes.</p>
<p class="versionadded">
<span class="versionmodified">New in version 3.3.</span> </p>
<dl class="describe">
<dt>
<tt class="descname">key in proxy</tt></dt>
<dd><p>Return <tt class="xref docutils literal"><span class="pre">True</span></tt> if the underlying mapping has a key <em>key</em>, else
<tt class="xref docutils literal"><span class="pre">False</span></tt>.</p>
</dd></dl>
<dl class="describe">
<dt>
<tt class="descname">proxy[key]</tt></dt>
<dd><p>Return the item of the underlying mapping with key <em>key</em>. Raises a
<a class="reference internal" href="exceptions.html#KeyError" title="KeyError"><tt class="xref py py-exc docutils literal"><span class="pre">KeyError</span></tt></a> if <em>key</em> is not in the underlying mapping.</p>
</dd></dl>
<dl class="describe">
<dt>
<tt class="descname">iter(proxy)</tt></dt>
<dd><p>Return an iterator over the keys of the underlying mapping. This is a
shortcut for <tt class="docutils literal"><span class="pre">iter(proxy.keys())</span></tt>.</p>
</dd></dl>
<dl class="describe">
<dt>
<tt class="descname">len(proxy)</tt></dt>
<dd><p>Return the number of items in the underlying mapping.</p>
</dd></dl>
<dl class="method">
<dt id="types.MappingProxyType.copy">
<tt class="descname">copy</tt><big>(</big><big>)</big><a class="headerlink" href="#types.MappingProxyType.copy" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a shallow copy of the underlying mapping.</p>
</dd></dl>
<dl class="method">
<dt id="types.MappingProxyType.get">
<tt class="descname">get</tt><big>(</big><em>key</em><span class="optional">[</span>, <em>default</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#types.MappingProxyType.get" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the value for <em>key</em> if <em>key</em> is in the underlying mapping, else
<em>default</em>. If <em>default</em> is not given, it defaults to <tt class="xref docutils literal"><span class="pre">None</span></tt>, so that
this method never raises a <a class="reference internal" href="exceptions.html#KeyError" title="KeyError"><tt class="xref py py-exc docutils literal"><span class="pre">KeyError</span></tt></a>.</p>
</dd></dl>
<dl class="method">
<dt id="types.MappingProxyType.items">
<tt class="descname">items</tt><big>(</big><big>)</big><a class="headerlink" href="#types.MappingProxyType.items" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a new view of the underlying mapping’s items (<tt class="docutils literal"><span class="pre">(key,</span> <span class="pre">value)</span></tt>
pairs).</p>
</dd></dl>
<dl class="method">
<dt id="types.MappingProxyType.keys">
<tt class="descname">keys</tt><big>(</big><big>)</big><a class="headerlink" href="#types.MappingProxyType.keys" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a new view of the underlying mapping’s keys.</p>
</dd></dl>
<dl class="method">
<dt id="types.MappingProxyType.values">
<tt class="descname">values</tt><big>(</big><big>)</big><a class="headerlink" href="#types.MappingProxyType.values" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a new view of the underlying mapping’s values.</p>
</dd></dl>
</dd></dl>
<dl class="class">
<dt id="types.SimpleNamespace">
<em class="property">class </em><tt class="descclassname">types.</tt><tt class="descname">SimpleNamespace</tt><a class="headerlink" href="#types.SimpleNamespace" title="Permalink to this definition">¶</a></dt>
<dd><p>A simple <a class="reference internal" href="functions.html#object" title="object"><tt class="xref py py-class docutils literal"><span class="pre">object</span></tt></a> subclass that provides attribute access to its
namespace, as well as a meaningful repr.</p>
<p>Unlike <a class="reference internal" href="functions.html#object" title="object"><tt class="xref py py-class docutils literal"><span class="pre">object</span></tt></a>, with <tt class="docutils literal"><span class="pre">SimpleNamespace</span></tt> you can add and remove
attributes. If a <tt class="docutils literal"><span class="pre">SimpleNamespace</span></tt> object is initialized with keyword
arguments, those are directly added to the underlying namespace.</p>
<p>The type is roughly equivalent to the following code:</p>
<div class="highlight-python3"><div class="highlight"><pre><span class="k">class</span> <span class="nc">SimpleNamespace</span><span class="p">:</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">__dict__</span><span class="o">.</span><span class="n">update</span><span class="p">(</span><span class="n">kwargs</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">__repr__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="n">keys</span> <span class="o">=</span> <span class="nb">sorted</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">__dict__</span><span class="p">)</span>
<span class="n">items</span> <span class="o">=</span> <span class="p">(</span><span class="s">"{}={!r}"</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">k</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">__dict__</span><span class="p">[</span><span class="n">k</span><span class="p">])</span> <span class="k">for</span> <span class="n">k</span> <span class="ow">in</span> <span class="n">keys</span><span class="p">)</span>
<span class="k">return</span> <span class="s">"{}({})"</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="nb">type</span><span class="p">(</span><span class="bp">self</span><span class="p">)</span><span class="o">.</span><span class="n">__name__</span><span class="p">,</span> <span class="s">", "</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">items</span><span class="p">))</span>
</pre></div>
</div>
<p><tt class="docutils literal"><span class="pre">SimpleNamespace</span></tt> may be useful as a replacement for <tt class="docutils literal"><span class="pre">class</span> <span class="pre">NS:</span> <span class="pre">pass</span></tt>.
However, for a structured record type use <a class="reference internal" href="collections.html#collections.namedtuple" title="collections.namedtuple"><tt class="xref py py-func docutils literal"><span class="pre">namedtuple()</span></tt></a>
instead.</p>
<p class="versionadded">
<span class="versionmodified">New in version 3.3.</span> </p>
</dd></dl>
</div>
</div>
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<h3><a href="../contents.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">8.9. <tt class="docutils literal"><span class="pre">types</span></tt> — Dynamic type creation and names for built-in types</a><ul>
<li><a class="reference internal" href="#dynamic-type-creation">8.9.1. Dynamic Type Creation</a></li>
<li><a class="reference internal" href="#standard-interpreter-types">8.9.2. Standard Interpreter Types</a></li>
</ul>
</li>
</ul>
<h4>Previous topic</h4>
<p class="topless"><a href="weakref.html"
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