Dialogs in PyQt4

Dialogs in PyQt4

Dialog windows or dialogs are an indispensable part of most modern GUI applications. A dialog is defined as a conversation between two or more persons. In a computer application a dialog is a window which is used to "talk" to the application. A dialog is used to input data, modify data, change the application settings etc. Dialogs are important means of communication between a user and a computer program.

QtGui.QInputDialog

The QtGui.QInputDialog provides a simple convenience dialog to get a single value from the user. The input value can be a string, a number or an item from a list.

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

"""
ZetCode PyQt4 tutorial 

In this example, we receive data from
a QtGui.QInputDialog dialog. 

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

import sys
from PyQt4 import QtGui


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

        self.btn = QtGui.QPushButton('Dialog', self)
        self.btn.move(20, 20)
        self.btn.clicked.connect(self.showDialog)
        
        self.le = QtGui.QLineEdit(self)
        self.le.move(130, 22)
        
        self.setGeometry(300, 300, 290, 150)
        self.setWindowTitle('Input dialog')
        self.show()
        
    def showDialog(self):
        
        text, ok = QtGui.QInputDialog.getText(self, 'Input Dialog', 
            'Enter your name:')
        
        if ok:
            self.le.setText(str(text))
        
def main():
    
    app = QtGui.QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())


if __name__ == '__main__':
    main()

The example has a button and a line edit widget. The button shows the input dialog for getting text values. The entered text will be displayed in the line edit widget.

text, ok = QtGui.QInputDialog.getText(self, 'Input Dialog', 
    'Enter your name:')

This line displays the input dialog. The first string is a dialog title, the second one is a message within the dialog. The dialog returns the entered text and a boolean value. If we clicked ok button, the boolean value is true, otherwise false.

if ok:
    self.le.setText(str(text))

The text that we have received from the dialog is set to the line edit widget.

Figure: Input Dialog

QtGui.QColorDialog

The QtGui.QColorDialog provides a dialog widget for selecting color values.

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

"""
ZetCode PyQt4 tutorial 

In this example, we select a color value
from the QtGui.QColorDialog and change the background
color of a QtGui.QFrame widget. 

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

import sys
from PyQt4 import QtGui

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

        col = QtGui.QColor(0, 0, 0) 

        self.btn = QtGui.QPushButton('Dialog', self)
        self.btn.move(20, 20)

        self.btn.clicked.connect(self.showDialog)

        self.frm = QtGui.QFrame(self)
        self.frm.setStyleSheet("QWidget { background-color: %s }" 
            % col.name())
        self.frm.setGeometry(130, 22, 100, 100)            
        
        self.setGeometry(300, 300, 250, 180)
        self.setWindowTitle('Color dialog')
        self.show()
        
    def showDialog(self):
      
        col = QtGui.QColorDialog.getColor()

        if col.isValid():
            self.frm.setStyleSheet("QWidget { background-color: %s }"
                % col.name())
        
def main():
    
    app = QtGui.QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())


if __name__ == '__main__':
    main()

The application example shows a push button and a QtGui.QFrame. The widget background is set to black color. Using the QtGui.QColorDialog, we can change its background.

col = QtGui.QColor(0, 0, 0) 

This is an initial color of the QtGui.QFrame background.

col = QtGui.QColorDialog.getColor()

This line will pop up the QtGui.QColorDialog.

if col.isValid():
    self.frm.setStyleSheet("QWidget { background-color: %s }"
        % col.name())

We check if the color is valid. If we click on the cancel button, no valid color is returned. If the color is valid, we change the background color using stylesheets.

Figure: Color dialog

QtGui.QFontDialog

The QtGui.QFontDialog is a dialog widget for selecting font.

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

"""
ZetCode PyQt4 tutorial 

In this example, we select a font name
and change the font of a label. 

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

import sys
from PyQt4 import QtGui


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

        vbox = QtGui.QVBoxLayout()

        btn = QtGui.QPushButton('Dialog', self)
        btn.setSizePolicy(QtGui.QSizePolicy.Fixed,
            QtGui.QSizePolicy.Fixed)
        
        btn.move(20, 20)

        vbox.addWidget(btn)

        btn.clicked.connect(self.showDialog)
        
        self.lbl = QtGui.QLabel('Knowledge only matters', self)
        self.lbl.move(130, 20)

        vbox.addWidget(self.lbl)
        self.setLayout(vbox)          
        
        self.setGeometry(300, 300, 250, 180)
        self.setWindowTitle('Font dialog')
        self.show()
        
    def showDialog(self):

        font, ok = QtGui.QFontDialog.getFont()
        if ok:
            self.lbl.setFont(font)
        
def main():
    
    app = QtGui.QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())


if __name__ == '__main__':
    main()

In our example, we have a button and a label. With QtGui.QFontDialog, we change the font of the label.

font, ok = QtGui.QFontDialog.getFont()

Here we pop up the font dialog. The getFont() method returns the font name and the ok parameter. It is equal to True if the user clicked OK; otherwise it is False.

if ok:
    self.label.setFont(font)

If we clicked ok, the font of the label would be changed.

QtGui.QFileDialog

The QtGui.QFileDialog is a dialog that allows users to select files or directories. The files can be selected for both opening and saving.

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

"""
ZetCode PyQt4 tutorial 

In this example, we select a file with a
QtGui.QFileDialog and display its contents
in a QtGui.QTextEdit.

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

import sys
from PyQt4 import QtGui


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

        self.textEdit = QtGui.QTextEdit()
        self.setCentralWidget(self.textEdit)
        self.statusBar()

        openFile = QtGui.QAction(QtGui.QIcon('open.png'), 'Open', self)
        openFile.setShortcut('Ctrl+O')
        openFile.setStatusTip('Open new File')
        openFile.triggered.connect(self.showDialog)

        menubar = self.menuBar()
        fileMenu = menubar.addMenu('&File')
        fileMenu.addAction(openFile)       
        
        self.setGeometry(300, 300, 350, 300)
        self.setWindowTitle('File dialog')
        self.show()
        
    def showDialog(self):

        fname = QtGui.QFileDialog.getOpenFileName(self, 'Open file', 
                '/home')
        
        f = open(fname, 'r')
        
        with f:        
            data = f.read()
            self.textEdit.setText(data) 
                                
        
def main():
    
    app = QtGui.QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())


if __name__ == '__main__':
    main()

The example shows a menubar, centrally set text edit widget and a statusbar. The menu item shows the QtGui.QFileDialog which is used to select a file. The contents of the file are loaded into the text edit widget.

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

The example is based on the QtGui.QMainWindow widget, because we centrally set the text edit widget.

fname = QtGui.QFileDialog.getOpenFileName(self, 'Open file', 
        '/home')

We pop up the QtGui.QFileDialog. The first string in the getOpenFileName() method is the caption. The second string specifies the dialog working directory. By default, the file filter is set to All files (*).

f = open(fname, 'r')

with f:        
    data = f.read()
    self.textEdit.setText(data) 

The selected file name is read and the contents of the file are set to the text edit widget.

Figure: File dialog

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In this part of the PyQt4 tutorial, we worked with dialogs.