Other Support for Dynamic Meta-objects

PyQt5 creates a QMetaObject instance for any Python sub-class of QObject without the need for the equivalent of Qt’s Q_OBJECT macro. Most of a QMetaObject is populated automatically by defining signals, slots and properties as described in previous sections. In this section we cover the ways in which the remaining parts of a QMetaObject are populated.

Note

Q_ENUM(), Q_FLAG() and Q_CLASSINFO() are not available when PyQt5 is built for PyPy.

Q_ENUM() and Q_FLAG()

New in version 5.11.

The Q_ENUM() and Q_FLAG() functions declare enumerated types and flag types respectively that are published in the QMetaObject. The typical use in PyQt5 is to declare symbolic constants that can be used by QML, and as type of properties that can be set in Qt Designer.

Each function takes a Python type object or an Enum object that implements the enumerated or flag type. For example:

from enum import Enum

from PyQt5.QtCore import Q_ENUM, Q_FLAG, QObject


class Instruction(QObject):

    class Direction(Enum):
        Up, Down, Left, Right = range(4)

    Q_ENUM(Direction)

    class Status:
        Null = 0x00
        Urgent = 0x01
        Acknowledged = 0x02
        Completed = 0x04

    Q_FLAG(Status)

New in version 5.2.

The (now deprecated) Q_ENUMS() and Q_FLAGS() functions are also provided. These differ from the above in that they can define multiple types in one invocation.

Q_CLASSINFO()

The Q_CLASSINFO() function is used in the same way as Qt’s macro of the same name, i.e. it is called from a class’s definition in order to specify a name/value pair that is placed in the class’s QMetaObject.

For example it is used by QML to define the default property of a class:

from PyQt5.QtCore import Q_CLASSINFO, QObject


class BirthdayParty(QObject):

    Q_CLASSINFO('DefaultProperty', 'guests')