# `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。

  在 3.13 版之後被棄用: Passing a file path instead of URL is soft deprecated. 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.

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

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.

    自從版本 3.14 後不推薦使用，將會自版本 3.16 中移除。: Invalid, undotted extensions will raise a `ValueError` in Python 3.16.

## 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