Question

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.

QInputDialog

The 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/python3
# -*- coding: utf-8 -*-

"""
ZetCode PyQt5 tutorial 

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

author: Jan Bodnar
website: zetcode.com 
last edited: January 2015
"""

import sys
from PyQt5.QtWidgets import (QWidget, QPushButton, QLineEdit, 
  QInputDialog, QApplication)


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

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

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 = 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 click the Ok button, the boolean value is true.

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

QColorDialog

The QColorDialog provides a dialog widget for selecting colour values.

#!/usr/bin/python3
# -*- coding: utf-8 -*-

"""
ZetCode PyQt5 tutorial 

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

author: Jan Bodnar
website: zetcode.com 
last edited: January 2015
"""

import sys
from PyQt5.QtWidgets import (QWidget, QPushButton, QFrame, 
  QColorDialog, QApplication)
from PyQt5.QtGui import QColor


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

    col = QColor(0, 0, 0) 

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

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

    self.frm = 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 = QColorDialog.getColor()

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

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

col = QColor(0, 0, 0) 

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

col = QColorDialog.getColor()

This line will pop up the QColorDialog .

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

We check if the colour is valid. If we click on the Cancel button, no valid colour is returned. If the colour is valid, we change the background colour using style sheets.

QFontDialog

The QFontDialog is a dialog widget for selecting a font.

#!/usr/bin/python3
# -*- coding: utf-8 -*-

"""
ZetCode PyQt5 tutorial 

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

author: Jan Bodnar
website: zetcode.com 
last edited: January 2015
"""

import sys
from PyQt5.QtWidgets import (QWidget, QVBoxLayout, QPushButton, 
  QSizePolicy, QLabel, QFontDialog, QApplication)


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

    vbox = QVBoxLayout()

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

    vbox.addWidget(btn)

    btn.clicked.connect(self.showDialog)
    
    self.lbl = 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 = QFontDialog.getFont()
    if ok:
      self.lbl.setFont(font)
    
    
if __name__ == '__main__':
  
  app = QApplication(sys.argv)
  ex = Example()
  sys.exit(app.exec_())

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

font, ok = 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.

Figure: Font dialog

QFileDialog

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

#!/usr/bin/python3
# -*- coding: utf-8 -*-

"""
ZetCode PyQt5 tutorial 

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

author: Jan Bodnar
website: zetcode.com 
last edited: January 2015
"""

import sys
from PyQt5.QtWidgets import (QMainWindow, QTextEdit, 
  QAction, QFileDialog, QApplication)
from PyQt5.QtGui import QIcon


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

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

    openFile = QAction(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 = QFileDialog.getOpenFileName(self, 'Open file', '/home')

    if fname[0]:
      f = open(fname[0], 'r')

      with f:
        data = f.read()
        self.textEdit.setText(data)    
    
if __name__ == '__main__':
  
  app = QApplication(sys.argv)
  ex = Example()
  sys.exit(app.exec_())

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(QMainWindow):
  
  def __init__(self):
    super().__init__()
    
    self.initUI()

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

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

We pop up the 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 (*).

if fname[0]:
  f = open(fname[0], '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

In this part of the PyQt5 tutorial, we worked with dialogs.