Describing PyQt4 widgets

Describing PyQt4 widgets

Here we will continue introducing PyQt4 widgets. We will cover QtGui.QPixmap, QtGui.QLineEdit, QtGui.QSplitter and QtGui.QComboBox.

QtGui.QPixmap

QtGui.QPixmap is one of the widgets used to work with images. It is optimized for showing images on screen. In our code example, we will use QtGui.QPixmap to display an image on the window.

#!/usr/bin/python
# -*- coding: utf-8 -*-

"""
ZetCode PyQt4 tutorial 

In this example, we dispay an image
on the window. 

author: Jan Bodnar
website: zetcode.com 
last edited: September 2011
"""

import sys
from PyQt4 import QtGui, QtCore

class Example(QtGui.QWidget):
    
    def __init__(self):
        super(Example, self).__init__()
        
        self.initUI()
        
    def initUI(self):      

        hbox = QtGui.QHBoxLayout(self)
        pixmap = QtGui.QPixmap("redrock.png")

        lbl = QtGui.QLabel(self)
        lbl.setPixmap(pixmap)

        hbox.addWidget(lbl)
        self.setLayout(hbox)
        
        self.move(300, 200)
        self.setWindowTitle('Red Rock')
        self.show()        
        
def main():
    
    app = QtGui.QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())


if __name__ == '__main__':
    main()    

In our example, we display an image on the window.

pixmap = QtGui.QPixmap("redrock.png")

We create a QtGui.QPixmap object. It takes the name of the file as a parameter.

lbl = QtGui.QLabel(self)
lbl.setPixmap(pixmap)

We put the pixmap into the QtGui.QLabel widget.

QtGui.QLineEdit

QtGui.QLineEdit is a widget that allows to enter and edit a single line of plain text. There are undo/redo, cut/paste and drag & drop functions available for QtGui.QLineEdit widget.

#!/usr/bin/python
# -*- coding: utf-8 -*-

"""
ZetCode PyQt4 tutorial 

This example shows text which 
is entered in a QtGui.QLineEdit
in a QtGui.QLabel widget.
 
author: Jan Bodnar
website: zetcode.com 
last edited: August 2011
"""

import sys
from PyQt4 import QtGui, QtCore

class Example(QtGui.QWidget):
    
    def __init__(self):
        super(Example, self).__init__()
        
        self.initUI()
        
    def initUI(self):      

        self.lbl = QtGui.QLabel(self)
        qle = QtGui.QLineEdit(self)
        
        qle.move(60, 100)
        self.lbl.move(60, 40)

        qle.textChanged[str].connect(self.onChanged)
        
        self.setGeometry(300, 300, 280, 170)
        self.setWindowTitle('QtGui.QLineEdit')
        self.show()
        
    def onChanged(self, text):
        
        self.lbl.setText(text)
        self.lbl.adjustSize()        
        
        
def main():
    
    app = QtGui.QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())


if __name__ == '__main__':
    main()

This example shows a line edit widget and a label. The text that we key in the line edit is displayed immediately in the label widget.

qle = QtGui.QLineEdit(self)

The QtGui.QLineEdit widget is created.

qle.textChanged[str].connect(self.onChanged)

If the text in the line edit widget changes, we call the onChanged() method.

def onChanged(self, text):
    
    self.lbl.setText(text)
    self.lbl.adjustSize() 

Inside the onChanged() method, we set the typed text to the label widget. We call the adjustSize() method to adjust the size of the label to the length of the text.

Figure: QtGui.QLineEdit

QtGui.QSplitter

QtGui.QSplitter lets the user control the size of child widgets by dragging the boundary between the children. In our example, we show three QtGui.QFrame widgets organized with two splitters.

#!/usr/bin/python
# -*- coding: utf-8 -*-

"""
ZetCode PyQt4 tutorial 

This example shows
how to use QtGui.QSplitter widget.
 
author: Jan Bodnar
website: zetcode.com 
last edited: September 2011
"""

import sys
from PyQt4 import QtGui, QtCore

class Example(QtGui.QWidget):
    
    def __init__(self):
        super(Example, self).__init__()
        
        self.initUI()
        
    def initUI(self):      

        hbox = QtGui.QHBoxLayout(self)

        topleft = QtGui.QFrame(self)
        topleft.setFrameShape(QtGui.QFrame.StyledPanel)
 
        topright = QtGui.QFrame(self)
        topright.setFrameShape(QtGui.QFrame.StyledPanel)

        bottom = QtGui.QFrame(self)
        bottom.setFrameShape(QtGui.QFrame.StyledPanel)

        splitter1 = QtGui.QSplitter(QtCore.Qt.Horizontal)
        splitter1.addWidget(topleft)
        splitter1.addWidget(topright)

        splitter2 = QtGui.QSplitter(QtCore.Qt.Vertical)
        splitter2.addWidget(splitter1)
        splitter2.addWidget(bottom)

        hbox.addWidget(splitter2)
        self.setLayout(hbox)
        QtGui.QApplication.setStyle(QtGui.QStyleFactory.create('Cleanlooks'))
        
        self.setGeometry(300, 300, 300, 200)
        self.setWindowTitle('QtGui.QSplitter')
        self.show()
        
    def onChanged(self, text):
        
        self.lbl.setText(text)
        self.lbl.adjustSize()        
        
        
def main():
    
    app = QtGui.QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())


if __name__ == '__main__':
    main()    

In our example we have three frame widgets and two splitters.

topleft = QtGui.QFrame(self)
topleft.setFrameShape(QtGui.QFrame.StyledPanel)

We use a styled frame in order to see boundaries between the QtGui.QFrame widgets.

splitter1 = QtGui.QSplitter(QtCore.Qt.Horizontal)
splitter1.addWidget(topleft)
splitter1.addWidget(topright)

We create a QtGui.QSplitter widget and add two frames into it.

splitter2 = QtGui.QSplitter(QtCore.Qt.Vertical)
splitter2.addWidget(splitter1)

We can also add splitter to another splitter widget.

QtGui.QApplication.setStyle(QtGui.QStyleFactory.create('Cleanlooks'))

We use a Cleanlooks style. In some styles the frames are not visible.

Figure: QtGui.QSplitter widget

QtGui.QComboBox

The QtGui.QComboBox is a widget that allows the user to choose from a list of options.

#!/usr/bin/python
# -*- coding: utf-8 -*-

"""
ZetCode PyQt4 tutorial 

This example shows
how to use QtGui.QComboBox widget.
 
author: Jan Bodnar
website: zetcode.com 
last edited: September 2011
"""

import sys
from PyQt4 import QtGui, QtCore

class Example(QtGui.QWidget):
    
    def __init__(self):
        super(Example, self).__init__()
        
        self.initUI()
        
    def initUI(self):      

        self.lbl = QtGui.QLabel("Ubuntu", self)

        combo = QtGui.QComboBox(self)
        combo.addItem("Ubuntu")
        combo.addItem("Mandriva")
        combo.addItem("Fedora")
        combo.addItem("Red Hat")
        combo.addItem("Gentoo")

        combo.move(50, 50)
        self.lbl.move(50, 150)

        combo.activated[str].connect(self.onActivated)        
         
        self.setGeometry(300, 300, 300, 200)
        self.setWindowTitle('QtGui.QComboBox')
        self.show()
        
    def onActivated(self, text):
      
        self.lbl.setText(text)
        self.lbl.adjustSize()  
                
def main():
    
    app = QtGui.QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())


if __name__ == '__main__':
    main()

The example shows a QtGui.QComboBox and a QtGui.QLabel. The combo box has a list of six options. These are the names of Linux distros. The label widget shows the selected option from the combo box.

combo = QtGui.QComboBox(self)
combo.addItem("Ubuntu")
combo.addItem("Mandriva")
combo.addItem("Fedora")
combo.addItem("Red Hat")
combo.addItem("Gentoo")

We create a QtGui.QComboBox widget and add five options into it.

combo.activated[str].connect(self.onActivated) 

Upon an item selection, we call the onActivated() method.

def onActivated(self, text):
  
    self.lbl.setText(text)
    self.lbl.adjustSize() 

Inside the method, we set the text of the chosen item to the label widget. We adjust the size of the label.

Figure: QtGui.QComboBox

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In this part of the PyQt4 tutorial, we covered other four PyQt4 widgets.