Support for Qt Properties — PyQt 4.11.4 Reference Guide

# 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`).