:mod:`types` --- Names for built-in types
=========================================

.. module:: types
   :synopsis: Names for built-in types.

**Source code:** :source:`Lib/types.py`

--------------

This module defines names for some object types that are used by the standard
Python interpreter, but not exposed as builtins like :class:`int` or
:class:`str` are.  Also, it does not include some of the types that arise
transparently during processing such as the ``listiterator`` type.

Typical use is for :func:`isinstance` or :func:`issubclass` checks.

The module defines the following names:

.. data:: FunctionType
          LambdaType

   The type of user-defined functions and functions created by :keyword:`lambda`
   expressions.


.. data:: GeneratorType

   The type of :term:`generator`-iterator objects, produced by calling a
   generator function.


.. data:: CodeType

   .. index:: builtin: compile

   The type for code objects such as returned by :func:`compile`.


.. data:: MethodType

   The type of methods of user-defined class instances.


.. data:: BuiltinFunctionType
          BuiltinMethodType

   The type of built-in functions like :func:`len` or :func:`sys.exit`, and
   methods of built-in classes.  (Here, the term "built-in" means "written in
   C".)


.. data:: ModuleType

   The type of modules.


.. data:: TracebackType

   The type of traceback objects such as found in ``sys.exc_info()[2]``.


.. data:: FrameType

   The type of frame objects such as found in ``tb.tb_frame`` if ``tb`` is a
   traceback object.


.. data:: GetSetDescriptorType

   The type of objects defined in extension modules with ``PyGetSetDef``, such
   as ``FrameType.f_locals`` or ``array.array.typecode``.  This type is used as
   descriptor for object attributes; it has the same purpose as the
   :class:`property` type, but for classes defined in extension modules.


.. data:: MemberDescriptorType

   The type of objects defined in extension modules with ``PyMemberDef``, such
   as ``datetime.timedelta.days``.  This type is used as descriptor for simple C
   data members which use standard conversion functions; it has the same purpose
   as the :class:`property` type, but for classes defined in extension modules.

   .. impl-detail::

      In other implementations of Python, this type may be identical to
      ``GetSetDescriptorType``.

.. class:: MappingProxyType(mapping)

   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.

   .. versionadded:: 3.3

   .. describe:: key in proxy

      Return ``True`` if the underlying mapping has a key *key*, else
      ``False``.

   .. describe:: proxy[key]

      Return the item of the underlying mapping with key *key*.  Raises a
      :exc:`KeyError` if *key* is not in the underlying mapping.

   .. describe:: iter(proxy)

      Return an iterator over the keys of the underlying mapping.  This is a
      shortcut for ``iter(proxy.keys())``.

   .. describe:: len(proxy)

      Return the number of items in the underlying mapping.

   .. method:: copy()

      Return a shallow copy of the underlying mapping.

   .. method:: get(key[, default])

      Return the value for *key* if *key* is in the underlying mapping, else
      *default*.  If *default* is not given, it defaults to ``None``, so that
      this method never raises a :exc:`KeyError`.

   .. method:: items()

      Return a new view of the underlying mapping's items (``(key, value)``
      pairs).

   .. method:: keys()

      Return a new view of the underlying mapping's keys.

   .. method:: values()

      Return a new view of the underlying mapping's values.