cpython/Doc/library/mimetypes.rst

:mod:`mimetypes` --- Map filenames to MIME types
================================================

.. module:: mimetypes
   :synopsis: Mapping of filename extensions to MIME types.
.. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org>


.. index:: pair: MIME; content type

The :mod:`mimetypes` module converts between a filename or URL and the MIME type
associated with the filename extension.  Conversions are provided from filename
to MIME type and from MIME type to filename extension; encodings are not
supported for the latter conversion.

The module provides one class and a number of convenience functions. The
functions are the normal interface to this module, but some applications may be
interested in the class as well.

The functions described below provide the primary interface for this module.  If
the module has not been initialized, they will call :func:`init` if they rely on
the information :func:`init` sets up.


.. function:: guess_type(filename[, strict])

   .. index:: pair: MIME; headers

   Guess the type of a file based on its filename or URL, given by *filename*.  The
   return value is a tuple ``(type, encoding)`` where *type* is ``None`` if the
   type can't be guessed (missing or unknown suffix) or a string of the form
   ``'type/subtype'``, usable for a MIME :mailheader:`content-type` header.

   *encoding* is ``None`` for no encoding or the name of the program used to encode
   (e.g. :program:`compress` or :program:`gzip`). The encoding is suitable for use
   as a :mailheader:`Content-Encoding` header, *not* as a
   :mailheader:`Content-Transfer-Encoding` header. The mappings are table driven.
   Encoding suffixes are case sensitive; type suffixes are first tried case
   sensitively, then case insensitively.

   Optional *strict* is a flag specifying whether the list of known MIME types
   is limited to only the official types `registered with IANA
   <http://www.isi.edu/in-notes/iana/assignments/media-types>`_ are recognized.
   When *strict* is true (the default), only the IANA types are supported; when
   *strict* is false, some additional non-standard but commonly used MIME types
   are also recognized.


.. function:: guess_all_extensions(type[, strict])

   Guess the extensions for a file based on its MIME type, given by *type*. The
   return value is a list of strings giving all possible filename extensions,
   including the leading dot (``'.'``).  The extensions are not guaranteed to have
   been associated with any particular data stream, but would be mapped to the MIME
   type *type* by :func:`guess_type`.

   Optional *strict* has the same meaning as with the :func:`guess_type` function.


.. function:: guess_extension(type[, strict])

   Guess the extension for a file based on its MIME type, given by *type*. The
   return value is a string giving a filename extension, including the leading dot
   (``'.'``).  The extension is not guaranteed to have been associated with any
   particular data stream, but would be mapped to the  MIME type *type* by
   :func:`guess_type`.  If no extension can be guessed for *type*, ``None`` is
   returned.

   Optional *strict* has the same meaning as with the :func:`guess_type` function.

Some additional functions and data items are available for controlling the
behavior of the module.


.. function:: init([files])

   Initialize the internal data structures.  If given, *files* must be a sequence
   of file names which should be used to augment the default type map.  If omitted,
   the file names to use are taken from :const:`knownfiles`.  Each file named in
   *files* or :const:`knownfiles` takes precedence over those named before it.
   Calling :func:`init` repeatedly is allowed.


.. function:: read_mime_types(filename)

   Load the type map given in the file *filename*, if it exists.  The  type map is
   returned as a dictionary mapping filename extensions, including the leading dot
   (``'.'``), to strings of the form ``'type/subtype'``.  If the file *filename*
   does not exist or cannot be read, ``None`` is returned.


.. function:: add_type(type, ext[, strict])

   Add a mapping from the mimetype *type* to the extension *ext*. When the
   extension is already known, the new type will replace the old one. When the type
   is already known the extension will be added to the list of known extensions.

   When *strict* is the mapping will added to the official MIME types, otherwise to
   the non-standard ones.


.. data:: inited

   Flag indicating whether or not the global data structures have been initialized.
   This is set to true by :func:`init`.


.. data:: knownfiles

   .. index:: single: file; mime.types

   List of type map file names commonly installed.  These files are typically named
   :file:`mime.types` and are installed in different locations by different
   packages.


.. data:: suffix_map

   Dictionary mapping suffixes to suffixes.  This is used to allow recognition of
   encoded files for which the encoding and the type are indicated by the same
   extension.  For example, the :file:`.tgz` extension is mapped to :file:`.tar.gz`
   to allow the encoding and type to be recognized separately.


.. data:: encodings_map

   Dictionary mapping filename extensions to encoding types.


.. data:: types_map

   Dictionary mapping filename extensions to MIME types.


.. data:: common_types

   Dictionary mapping filename extensions to non-standard, but commonly found MIME
   types.

The :class:`MimeTypes` class may be useful for applications which may want more
than one MIME-type database:


.. class:: MimeTypes([filenames])

   This class represents a MIME-types database.  By default, it provides access to
   the same database as the rest of this module. The initial database is a copy of
   that provided by the module, and may be extended by loading additional
   :file:`mime.types`\ -style files into the database using the :meth:`read` or
   :meth:`readfp` methods.  The mapping dictionaries may also be cleared before
   loading additional data if the default data is not desired.

   The optional *filenames* parameter can be used to cause additional files to be
   loaded "on top" of the default database.

   .. versionadded:: 2.2

An example usage of the module::

   >>> import mimetypes
   >>> mimetypes.init()
   >>> mimetypes.knownfiles
   ['/etc/mime.types', '/etc/httpd/mime.types', ... ]
   >>> mimetypes.suffix_map['.tgz']
   '.tar.gz'
   >>> mimetypes.encodings_map['.gz']
   'gzip'
   >>> mimetypes.types_map['.tgz']
   'application/x-tar-gz'


.. _mimetypes-objects:

MimeTypes Objects
-----------------

:class:`MimeTypes` instances provide an interface which is very like that of the
:mod:`mimetypes` module.


.. attribute:: MimeTypes.suffix_map

   Dictionary mapping suffixes to suffixes.  This is used to allow recognition of
   encoded files for which the encoding and the type are indicated by the same
   extension.  For example, the :file:`.tgz` extension is mapped to :file:`.tar.gz`
   to allow the encoding and type to be recognized separately.  This is initially a
   copy of the global ``suffix_map`` defined in the module.


.. attribute:: MimeTypes.encodings_map

   Dictionary mapping filename extensions to encoding types.  This is initially a
   copy of the global ``encodings_map`` defined in the module.


.. attribute:: MimeTypes.types_map

   Dictionary mapping filename extensions to MIME types.  This is initially a copy
   of the global ``types_map`` defined in the module.


.. attribute:: MimeTypes.common_types

   Dictionary mapping filename extensions to non-standard, but commonly found MIME
   types.  This is initially a copy of the global ``common_types`` defined in the
   module.


.. method:: MimeTypes.guess_extension(type[, strict])

   Similar to the :func:`guess_extension` function, using the tables stored as part
   of the object.


.. method:: MimeTypes.guess_type(url[, strict])

   Similar to the :func:`guess_type` function, using the tables stored as part of
   the object.


.. method:: MimeTypes.read(path)

   Load MIME information from a file named *path*.  This uses :meth:`readfp` to
   parse the file.


.. method:: MimeTypes.readfp(file)

   Load MIME type information from an open file.  The file must have the format of
   the standard :file:`mime.types` files.