Support for Qt Properties

PyQt4 does not support the setting and getting of Qt properties as if they were normal instance attributes. This is because the name of a property often conflicts with the name of the property’s getter method.

However, PyQt4 does support the initial setting of properties using keyword arguments passed when an instance is created. For example:

act = QtGui.QAction("&Save", self, shortcut=QtGui.QKeySequence.Save,
        statusTip="Save the document to disk", triggered=self.save)

The example also demonstrates the use of a keyword argument to connect a signal to a slot.

PyQt4 also supports setting the values of properties (and connecting a signal to a slot) using the pyqtConfigure() method of QObject. For example, the following gives the same results as above:

act = QtGui.QAction("&Save", self)
act.pyqtConfigure(shortcut=QtGui.QKeySequence.Save,
        statusTip="Save the document to disk", triggered=self.save)

Defining New Qt Properties

A new Qt property may be defined using the pyqtProperty() function. It is used in the same way as the standard Python property() function. In fact, Qt properties defined in this way also behave as Python properties.

PyQt4.QtCore.pyqtProperty(type[, fget=None[, fset=None[, freset=None[, fdel=None[, doc=None[, designable=True[, scriptable=True[, stored=True[, user=False[, constant=False[, final=False[, notify=None]]]]]]]]]]]])

Create a property that behaves as both a Python property and a Qt property.

Parameters:

• type – the type of the property. It is either a Python type object or a string that is the name of a C++ type.
• fget – the optional callable used to get the value of the property.
• fset – the optional callable used to set the value of the property.
• freset – the optional callable used to reset the value of the property to its default value. It is ignored by Python
• fdel – the optional callable used to delete the property. It is ignored by Qt.
• doc – the optional docstring of the property. It is ignored by Qt.
• designable – optionally sets the Qt DESIGNABLE flag. It is ignored by Python
• scriptable – optionally sets the Qt SCRIPTABLE flag. It is ignored by Python
• stored – optionally sets the Qt STORED flag. It is ignored by Python
• user – optionally sets the Qt USER flag. It is ignored by Python
• constant – optionally sets the Qt CONSTANT flag. It is ignored by Python
• final – optionally sets the Qt FINAL flag. It is ignored by Python
• notify – the optional unbound notify signal. It is ignored by Python

Return type:

the property object.

It is also possible to use pyqtProperty() as a decorator in the same way as the standard Python property() function. The following example shows how to define an int property with a getter and setter:

from PyQt4.QtCore import QObject, pyqtProperty

class Foo(QObject):

    def __init__(self):
        QObject.__init__(self)

        self._total = 0

    @pyqtProperty(int)
    def total(self):
        return self._total

    @total.setter
    def total(self, value):
        self._total = value

If you prefer the Qt terminology you may also use write instead of setter (and read instead of getter).