QMimeDatabase

The QMimeDatabase class maintains a database of MIME types. More

Inheritance diagram of PySide2.QtCore.QMimeDatabase

New in version 5.0.

Synopsis

Functions

Detailed Description

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
}

See also

QMimeType MIME Type Browser Example

class QMimeDatabase

Constructs a QMimeDatabase object.

It is perfectly OK to create an instance of QMimeDatabase every time you need to perform a lookup. The parsing of mimetypes is done on demand (when shared-mime-info is installed) or when the very first instance is constructed (when parsing XML files directly).

PySide2.QtCore.QMimeDatabase.MatchMode

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

Constant

Description

QMimeDatabase.MatchDefault

Both the file name and content are used to look for a match

QMimeDatabase.MatchExtension

Only the file name is used to look for a match

QMimeDatabase.MatchContent

The file content is used to look for a match

PySide2.QtCore.QMimeDatabase.allMimeTypes()
Return type

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 mimeTypeForXxx() methods for performance reasons.

PySide2.QtCore.QMimeDatabase.mimeTypeForData(device)
Parameters

deviceQIODevice

Return type

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.

PySide2.QtCore.QMimeDatabase.mimeTypeForData(data)
Parameters

dataQByteArray

Return type

QMimeType

PySide2.QtCore.QMimeDatabase.mimeTypeForFile(fileInfo[, mode=MatchDefault])
Parameters
Return type

QMimeType

PySide2.QtCore.QMimeDatabase.mimeTypeForFile(fileName[, mode=MatchDefault])
Parameters
Return type

QMimeType

PySide2.QtCore.QMimeDatabase.mimeTypeForFileNameAndData(fileName, device)
Parameters
Return type

QMimeType

PySide2.QtCore.QMimeDatabase.mimeTypeForFileNameAndData(fileName, data)
Parameters
Return type

QMimeType

PySide2.QtCore.QMimeDatabase.mimeTypeForName(nameOrAlias)
Parameters

nameOrAlias – unicode

Return type

QMimeType

Returns a MIME type for nameOrAlias or an invalid one if none found.

PySide2.QtCore.QMimeDatabase.mimeTypeForUrl(url)
Parameters

urlQUrl

Return type

QMimeType

Returns a MIME type for url .

If the URL is a local file, this calls mimeTypeForFile .

Otherwise the matching is done based on the file name only, except for schemes where file names don’t mean much, like HTTP. This method always returns the default mimetype for HTTP URLs, use QNetworkAccessManager to handle HTTP URLs properly.

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

PySide2.QtCore.QMimeDatabase.mimeTypesForFileName(fileName)
Parameters

fileName – unicode

Return type

Returns the MIME types for the file name fileName .

If the file name doesn’t match any known pattern, an empty list is returned. If multiple MIME types match this file, they are all returned.

This function does not try to open the file. To also use the content when determining the MIME type, use mimeTypeForFile() or mimeTypeForFileNameAndData() instead.

PySide2.QtCore.QMimeDatabase.suffixForFileName(fileName)
Parameters

fileName – unicode

Return type

unicode

Returns the suffix for the file fileName , as known by the MIME database.

This allows to pre-select “tar.bz2” for foo.tar.bz2, but still only “txt” for my.file.with.dots.txt.