QMimeDatabase¶

PyQt5.QtCore.QMimeDatabase

Description¶

The QMimeDatabase class maintains a database of MIME types.

The MIME type database is provided by the freedesktop.org shared-mime-info project. If the MIME type database cannot be found on the system, as is the case on most Windows, macOS, and iOS systems, Qt will use its own copy of it.

Applications which want to define custom MIME types need to install an XML file into the locations searched for MIME definitions. These locations can be queried with

# QStandardPaths::locateAll(QStandardPaths::GenericDataLocation, QLatin1String("mime/packages"),
#                           QStandardPaths::LocateDirectory);

On a typical Unix system, this will be /usr/share/mime/packages/, but it is also possible to extend the list of directories by setting the environment variable XDG_DATA_DIRS. For instance adding /opt/myapp/share to XDG_DATA_DIRS will result in /opt/myapp/share/mime/packages/ being searched for MIME definitions.

Here is an example of MIME XML:

# <?xml version="1.0" encoding="UTF-8"?>
# <mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
#   <mime-type type="application/vnd.qt.qmakeprofile">
#     <comment xml:lang="en">Qt qmake Profile</comment>
#     <glob pattern="*.pro" weight="50"/>
#   </mime-type>
# </mime-info>

For more details about the syntax of XML MIME definitions, including defining “magic” in order to detect MIME types based on data as well, read the Shared Mime Info specification at http://standards.freedesktop.org/shared-mime-info-spec/shared-mime-info-spec-latest.html

On Unix systems, a binary cache is used for more performance. This cache is generated by the command “update-mime-database path”, where path would be /opt/myapp/share/mime in the above example. Make sure to run this command when installing the MIME type definition file.

# QMimeDatabase db;
# QMimeType mime = db.mimeTypeForFile(fileName);
# if (mime.inherits("text/plain")) {
#     // The file is plain text, we can display it in a QTextEdit
# }

Enums¶

MatchMode

This enum specifies how matching a file to a MIME type is performed.

Member	Value	Description
MatchContent	0x2	The file content is used to look for a match
MatchDefault	0x0	Both the file name and content are used to look for a match
MatchExtension	0x1	Only the file name is used to look for a match

Methods¶

__init__(): TODO

allMimeTypes() → List[QMimeType]

Returns the list of all available MIME types.

This can be useful for showing all MIME types to the user, for instance in a MIME type editor. Do not use unless really necessary in other cases though, prefer using the mimeTypeForData() methods for performance reasons.

mimeTypeForData(Union[QByteArray, bytes, bytearray]) → QMimeType

Returns a MIME type for data.

A valid MIME type is always returned. If data doesn’t match any known MIME type data, the default MIME type (application/octet-stream) is returned.

mimeTypeForData(QIODevice) → QMimeType

Returns a MIME type for the data in device.

A valid MIME type is always returned. If the data in device doesn’t match any known MIME type data, the default MIME type (application/octet-stream) is returned.

mimeTypeForFile(str, mode: MatchMode = MatchDefault) → QMimeType

Returns a MIME type for the file named fileName using mode.

This is an overloaded function.

mimeTypeForFile(QFileInfo, mode: MatchMode = MatchDefault) → QMimeType

Returns a MIME type for fileInfo.

A valid MIME type is always returned.

The default matching algorithm looks at both the file name and the file contents, if necessary. The file extension has priority over the contents, but the contents will be used if the file extension is unknown, or matches multiple MIME types. If fileInfo is a Unix symbolic link, the file that it refers to will be used instead. If the file doesn’t match any known pattern or data, the default MIME type (application/octet-stream) is returned.

When mode is set to MatchExtension, only the file name is used, not the file contents. The file doesn’t even have to exist. If the file name doesn’t match any known pattern, the default MIME type (application/octet-stream) is returned. If multiple MIME types match this file, the first one (alphabetically) is returned.

When mode is set to MatchContent, and the file is readable, only the file contents are used to determine the MIME type. This is equivalent to calling mimeTypeForData() with a QFile as input device.

fileInfo may refer to an absolute or relative path.