qpushbutton signals

PyQt4 button example

PyQt4 (Qt4) supports buttons through the QPushButton widget.

We extend the code to display a button in the center of the window.

The button will show a tooltip if hovered and when pressed will close the program.

Related course:

• Create GUI Apps with PyQt5

PyQt4 button example

The example below adds a button to a PyQt4 window.

#! /usr/bin/env python
# -*- coding: utf-8 -*-
#
import sys
from PyQt4.QtGui import *

# Create an PyQT4 application object.
a = QApplication(sys.argv)

# The QWidget widget is the base class of all user interface objects in PyQt4.
w = QWidget()

# Set window size.
w.resize(320, 240)

# Set window title
w.setWindowTitle("Hello World!")

# Add a button
btn = QPushButton('Hello World!', w)
btn.setToolTip('Click to quit!')
btn.clicked.connect(exit)
btn.resize(btn.sizeHint())
btn.move(100, 80)

# Show window
w.show()

sys.exit(a.exec_())

PyQt4 signals and slots

A button click should do something. To do so, you must use signals and slots.

If a user does an action such as clicking on a button, typing text in a box – the widget sends out a signal. Signals can be connected with a slot, that acts as a receiver and acts on it.

import sys
from PyQt4.QtCore import pyqtSlot
from PyQt4.QtGui import *

# create our window
app = QApplication(sys.argv)
w = QWidget()
w.setWindowTitle('Button click example @pythonspot.com')

# Create a button in the window
btn = QPushButton('Click me', w)

# Create the actions
@pyqtSlot()
def on_click():
    print('clicked')

@pyqtSlot()
def on_press():
    print('pressed')

@pyqtSlot()
def on_release():
    print('released')

# connect the signals to the slots
btn.clicked.connect(on_click)
btn.pressed.connect(on_press)
btn.released.connect(on_release)

# Show the window and run the app
w.show()
app.exec_()

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