"mimetypes" --- 將檔案名稱對映到 MIME 類型
******************************************

**原始碼：**Lib/mimetypes.py

======================================================================

The "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
"init()" if they rely on the information "init()" sets up.

mimetypes.guess_type(url, strict=True)

   Guess the type of a file based on its filename, path or URL, given
   by *url*. URL can be a string or a *path-like object*.

   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 *content-
   type* header.

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

   The optional *strict* argument is a flag specifying whether the
   list of known MIME types is limited to only the official types
   registered with IANA. However, the behavior of this module also
   depends on the underlying operating system. Only file types
   recognized by the OS or explicitly registered with Python's
   internal database can be identified. 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.

   在 3.8 版的變更: 新增 *url* 做為 *path-like object* 的支援。

   Soft deprecated since version 3.13: Passing a file path instead of
   URL. Use "guess_file_type()" for this.

mimetypes.guess_file_type(path, *, strict=True)

   Guess the type of a file based on its path, given by *path*.
   Similar to the "guess_type()" function, but accepts a path instead
   of URL. Path can be a string, a bytes object or a *path-like
   object*.

   在 3.13 版被加入.

mimetypes.guess_all_extensions(type, strict=True)

   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 "guess_type()" and "guess_file_type()".

   The optional *strict* argument has the same meaning as with the
   "guess_type()" function.

mimetypes.guess_extension(type, strict=True)

   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 "guess_type()" and
   "guess_file_type()". If no extension can be guessed for *type*,
   "None" is returned.

   The optional *strict* argument has the same meaning as with the
   "guess_type()" function.

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

mimetypes.init(files=None)

   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
   "knownfiles"; on Windows, the current registry settings are loaded.
   Each file named in *files* or "knownfiles" takes precedence over
   those named before it.  Calling "init()" repeatedly is allowed.

   Specifying an empty list for *files* will prevent the system
   defaults from being applied: only the well-known values will be
   present from a built-in list.

   If *files* is "None" the internal data structure is completely
   rebuilt to its initial default value. This is a stable operation
   and will produce the same results when called multiple times.

   在 3.2 版的變更: 先前 Windows 登錄設定會被忽略。

mimetypes.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.

mimetypes.add_type(type, ext, strict=True)

   Add a mapping from the MIME type *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. Valid extensions are empty or
   start with a "'.'".

   When *strict* is "True" (the default), the mapping will be added to
   the official MIME types, otherwise to the non-standard ones.

   在 3.14 版之後被棄用: *ext* values that do not start with "'.'" are
   deprecated.

   在 3.16.0a0 (unreleased) 版的變更: *ext* now must start with "'.'".
   Otherwise "ValueError" is raised.

mimetypes.inited

   Flag indicating whether or not the global data structures have been
   initialized. This is set to "True" by "init()".

mimetypes.knownfiles

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

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 ".tgz"
   extension is mapped to ".tar.gz" to allow the encoding and type to
   be recognized separately.

mimetypes.encodings_map

   Dictionary mapping filename extensions to encoding types.

mimetypes.types_map

   Dictionary mapping filename extensions to MIME types.

mimetypes.common_types

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

模組的使用範例：

   >>> 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 物件
==============

The "MimeTypes" class may be useful for applications which may want
more than one MIME-type database; it provides an interface similar to
the one of the "mimetypes" module.

class mimetypes.MimeTypes(filenames=(), strict=True)

   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 "mime.types"-style files into
   the database using the "read()" or "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.

   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 ".tgz"
      extension is mapped to ".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.

   encodings_map

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

   types_map

      Tuple containing two dictionaries, mapping filename extensions
      to MIME types: the first dictionary is for the non-standards
      types and the second one is for the standard types. They are
      initialized by "common_types" and "types_map".

   types_map_inv

      Tuple containing two dictionaries, mapping MIME types to a list
      of filename extensions: the first dictionary is for the non-
      standards types and the second one is for the standard types.
      They are initialized by "common_types" and "types_map".

   guess_extension(type, strict=True)

      Similar to the "guess_extension()" function, using the tables
      stored as part of the object.

   guess_type(url, strict=True)

      Similar to the "guess_type()" function, using the tables stored
      as part of the object.

   guess_file_type(path, *, strict=True)

      Similar to the "guess_file_type()" function, using the tables
      stored as part of the object.

      在 3.13 版被加入.

   guess_all_extensions(type, strict=True)

      Similar to the "guess_all_extensions()" function, using the
      tables stored as part of the object.

   read(filename, strict=True)

      Load MIME information from a file named *filename*.  This uses
      "readfp()" to parse the file.

      If *strict* is "True", information will be added to list of
      standard types, else to the list of non-standard types.

   readfp(fp, strict=True)

      Load MIME type information from an open file *fp*.  The file
      must have the format of the standard "mime.types" files.

      If *strict* is "True", information will be added to the list of
      standard types, else to the list of non-standard types.

   read_windows_registry(strict=True)

      Load MIME type information from the Windows registry.

      可用性: Windows.

      If *strict* is "True", information will be added to the list of
      standard types, else to the list of non-standard types.

      在 3.2 版被加入.

   add_type(type, ext, strict=True)

      Add a mapping from the MIME type *type* to the extension *ext*.
      Valid extensions start with a '.' or are empty. 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 "True" (the default), the mapping will be added
      to the official MIME types, otherwise to the non-standard ones.

      在 3.14 版之後被棄用: *ext* values that do not start with "'.'"
      are deprecated.

      在 3.16.0a0 (unreleased) 版的變更: *ext* now must start with
      "'.'". Otherwise "ValueError" is raised.


命令列用法
==========

The "mimetypes" module can be executed as a script from the command
line.

   python -m mimetypes [-h] [-e] [-l] type [type ...]

The following options are accepted:

-h
--help

   Show the help message and exit.

-e
--extension

   Guess extension instead of type.

-l
--lenient

   Additionally search for some common, but non-standard types.

By default the script converts MIME types to file extensions. However,
if "--extension" is specified, it converts file extensions to MIME
types.

For each "type" entry, the script writes a line into the standard
output stream. If an unknown type occurs, it writes an error message
into the standard error stream and exits with the return code "1".


Command-line example
====================

Here are some examples of typical usage of the "mimetypes" command-
line interface:

   $ # get a MIME type by a file name
   $ python -m mimetypes filename.png
   type: image/png encoding: None

   $ # get a MIME type by a URL
   $ python -m mimetypes https://example.com/filename.txt
   type: text/plain encoding: None

   $ # get a complex MIME type
   $ python -m mimetypes filename.tar.gz
   type: application/x-tar encoding: gzip

   $ # get a MIME type for a rare file extension
   $ python -m mimetypes filename.pict
   error: unknown extension of filename.pict

   $ # now look in the extended database built into Python
   $ python -m mimetypes --lenient filename.pict
   type: image/pict encoding: None

   $ # get a file extension by a MIME type
   $ python -m mimetypes --extension text/javascript
   .js

   $ # get a file extension by a rare MIME type
   $ python -m mimetypes --extension text/xul
   error: unknown type text/xul

   $ # now look in the extended database again
   $ python -m mimetypes --extension --lenient text/xul
   .xul

   $ # try to feed an unknown file extension
   $ python -m mimetypes filename.sh filename.nc filename.xxx filename.txt
   type: application/x-sh encoding: None
   type: application/x-netcdf encoding: None
   error: unknown extension of filename.xxx

   $ # try to feed an unknown MIME type
   $ python -m mimetypes --extension audio/aac audio/opus audio/future audio/x-wav
   .aac
   .opus
   error: unknown type audio/future
