PyQt Tutorial

Qt Debug Signal And Slot
Qt Connect Signal Slot
Qt Signal Slot Example

PyQt Useful Resources

Signals and slots are used for communication between objects. The signals and slots mechanism is a central feature of Qt and probably the part that differs most from the features provided by other frameworks. In GUI programming, when we change one widget. New-style Signal and Slot Support¶. This section describes the new style of connecting signals and slots introduced in PyQt4 v4.5. One of the key features of Qt is its.

Selected Reading

Unlike a console mode application, which is executed in a sequential manner, a GUI based application is event driven. Functions or methods are executed in response to user’s actions like clicking on a button, selecting an item from a collection or a mouse click etc., called events.

Widgets used to build the GUI interface act as the source of such events. Each PyQt widget, which is derived from QObject class, is designed to emit ‘signal’ in response to one or more events. The signal on its own does not perform any action. Instead, it is ‘connected’ to a ‘slot’. The slot can be any callable Python function.

In PyQt, connection between a signal and a slot can be achieved in different ways. Following are most commonly used techniques −

A more convenient way to call a slot_function, when a signal is emitted by a widget is as follows −

The worker thread is implemented as a PyQt thread rather than a Python thread since we want to take advantage of the signals and slots mechanism to communicate with the. It is called by Qt once the # thread environment has been set up. PyQt/Threading,SignalsandSlots (last edited 2014-06-04 21:48:33 by DavidBoddie) MoinMoin Powered.

Suppose if a function is to be called when a button is clicked. Here, the clicked signal is to be connected to a callable function. It can be achieved in any of the following two techniques −

or

Example

Qt Debug Signal And Slot

In the following example, two QPushButton objects (b1 and b2) are added in QDialog window. We want to call functions b1_clicked() and b2_clicked() on clicking b1 and b2 respectively.

When b1 is clicked, the clicked() signal is connected to b1_clicked() function

When b2 is clicked, the clicked() signal is connected to b2_clicked() function

Example

Qt Connect Signal Slot

The above code produces the following output −

Qt Signal Slot Example

Output

Python Qt Signals And Slots