Qt for Python Tutorial ClickableButton: Difference between revisions

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== A simple clickable button tutorial ==


[[Category:LanguageBindings::PySide]]
In this tutorial, we'll show you how to start handling with Qt for Python's '''signals and slots'''.
Basically, this Qt feature allows your graphical widgets to communicate with other graphical widgets or your own python code.
Our application will create a clickable button which will show '''Button clicked, Hello!''' in the python console each time you click it.


'''English''' [[PySideTutorials_Clickable_button_Japanese|日本語]]
Let's starting by importing the necessary PySide2 classes and python sys module:


= A simple clickable button tutorial =
<syntaxhighlight lang="python" line='line'>
 
In this tutorial, we'll show you how to start handling with PySide's '''signals and slots'''. Basically, this Qt feature allows your graphical widgets to communicate with other graphical widgets or your own python code. Our application will create a clickable button which will show '''Hello World''' in the python console each time you press it.
 
Let's starting by importing the necessary Qt classes and python sys class:
 
<code>
import sys
import sys
from PySide.QtCore import *
from PySide2.QtWidgets import QApplication, QPushButton                                                                                                                                                                                                                                                                 
from PySide.QtGui import *
</syntaxhighlight>
</code>


Let's also create a python function which writes "Hello World" to the console:
Let's also create a python function which writes the message to the console:


<code>
<syntaxhighlight lang="python" line='line'>
# Greetings
# Greetings
def sayHello():
def say_hello():                                                                                    
print "Hello World!"
    print("Button clicked, Hello!")
</code>
</syntaxhighlight>


Now, as mentioned in [[Hello_World_in_PySide|Your first PySide application]], you must create the QApplication which will run your PySide code:
Now, as mentioned in previous examples you must create the QApplication which will run your PySide2 code:


<code>
<syntaxhighlight lang="python" line='line'>
# Create the Qt Application
# Create the Qt Application
app = QApplication(sys.argv)
app = QApplication(sys.argv)
</code>
</syntaxhighlight>


Let's create the clickable button, a QPushButton. We pass a python string on the constructor which will label the button:
Let's create the clickable button, a QPushButton.
We pass a python string on the constructor which will label the button:


<code>
<syntaxhighlight lang="python" line='line'>
# Create a button
# Create a button
button = QPushButton("Click me")
button = QPushButton("Click me")
</code>
</syntaxhighlight>


Before we show the button, we must connect it to the '''sayHello()''' function that we defined previously. For now, there are two ways of doing this - by using the old style or the new style. The new style is more pythonic and that's what we'll use here. You can find more information about both approaches in [[Signals_and_Slots_in_PySide]]. The QPushButton has a predefined signal called '''clicked''' which is triggered every time that the button is pressed. We'll just connect this signal to the '''sayHello()''' function:
Before we show the button, we must connect it to the '''say_hello()''' function that we defined previously.
For now, there are two ways of doing this - by using the old style or the new style.
The new style is more pythonic and that's what we'll use here.
You can find more information about both approaches in [[Signals_and_Slots_in_PySide]].
The QPushButton has a predefined signal called '''clicked''' which is triggered every time that the button is pressed.
We'll just connect this signal to the '''say_hello()''' function:


<code>
<syntaxhighlight lang="python" line='line'>
# Connect the button to the function
# Connect the button to the function
button.clicked.connect(sayHello)
button.clicked.connect(say_hello)
</code>
</syntaxhighlight>


Finally, we show the button and start the Qt main loop:
Finally, we show the button and start the Qt main loop:


<code>
<syntaxhighlight lang="python" line='line'>
# Show the button
# Show the button
button.show()
button.show()
# Run the main Qt loop
# Run the main Qt loop
app.exec_()
app.exec_()
</code>
</syntaxhighlight>


== Full Code ==
== Full Code ==


<code>
<syntaxhighlight lang="python" line='line'>
#!/usr/bin/python
#!/usr/bin/python
# -'''- coding: utf-8 -'''-
# -'''- coding: utf-8 -'''-


import sys                                                                                         
from PySide2.QtWidgets import QApplication, QPushButton                                                                                                                                                                                                                                                                 
                                                                                                   
def say_hello():                                                                                   
print("Button clicked, Hello!")                                                                   
                                                                                                   
# Create the Qt Application                                                                       
app = QApplication(sys.argv)                                                                       
# Create a button, connect it and show it                                                         
button = QPushButton("Click me")                                                                   
button.clicked.connect(say_hello)                                                                   
button.show()                                                                                     
# Run the main Qt loop                                                                             
app.exec_()
</syntaxhighlight>
== A button to exit the application ==
Following the same idea, we can create a a QPushButton that closes the application when clicked.
<syntaxhighlight lang="python" line='line'>
from PySide2.QtWidgets import QApplication, QPushButton
if __name__ == "__main__":
    # Create a QApplication
    app = QApplication([])
    # Create a button
    button = QPushButton('Exit')
    # Connect the button "clicked" signal to the exit() method
    # that finishes the QApplication
    button.clicked.connect(app.exit)
    button.show()
    app.exec_()
</syntaxhighlight>
= Another example =
Take a look of the following code,
it follows the same idea previously described but interacting with other python modules
<syntaxhighlight lang="python" line='line'>
import sys
import sys
from PySide.QtCore import *
import random
from PySide.QtGui import *
from PySide2 import QtCore, QtWidgets, QtGui
 
class MyWidget(QtWidgets.QWidget):
    def __init__(self):
        QtWidgets.QWidget.__init__(self)
 
        self.hello = ["Hallo Welt", "你好,世界", "Hei maailma",
            "Hola Mundo", "Привет мир"]
 
        self.button = QtWidgets.QPushButton("Click me!")
        self.text = QtWidgets.QLabel("Hello World")
        self.text.setAlignment(QtCore.Qt.AlignCenter)
 
        self.layout = QtWidgets.QVBoxLayout()
        self.layout.addWidget(self.text)
        self.layout.addWidget(self.button)
        self.setLayout(self.layout)
 
        self.button.clicked.connect(self.magic)
 
 
    def magic(self):
        self.text.setText(random.choice(self.hello))
 
 
if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
 
    widget = MyWidget()
    widget.show()


def sayHello():
    sys.exit(app.exec_())
print "Hello World!"


# Create the Qt Application
</syntaxhighlight>
app = QApplication(sys.argv)
# Create a button, connect it and show it
button = QPushButton("Click me")
button.clicked.connect(sayHello)
button.show()
# Run the main Qt loop
app.exec_()
</code>

Latest revision as of 12:44, 11 July 2022

A simple clickable button tutorial

In this tutorial, we'll show you how to start handling with Qt for Python's signals and slots. Basically, this Qt feature allows your graphical widgets to communicate with other graphical widgets or your own python code. Our application will create a clickable button which will show Button clicked, Hello! in the python console each time you click it.

Let's starting by importing the necessary PySide2 classes and python sys module:

import sys
from PySide2.QtWidgets import QApplication, QPushButton

Let's also create a python function which writes the message to the console:

# Greetings
def say_hello():                                                                                     
    print("Button clicked, Hello!")

Now, as mentioned in previous examples you must create the QApplication which will run your PySide2 code:

# Create the Qt Application
app = QApplication(sys.argv)

Let's create the clickable button, a QPushButton. We pass a python string on the constructor which will label the button:

# Create a button
button = QPushButton("Click me")

Before we show the button, we must connect it to the say_hello() function that we defined previously. For now, there are two ways of doing this - by using the old style or the new style. The new style is more pythonic and that's what we'll use here. You can find more information about both approaches in Signals_and_Slots_in_PySide. The QPushButton has a predefined signal called clicked which is triggered every time that the button is pressed. We'll just connect this signal to the say_hello() function:

# Connect the button to the function
button.clicked.connect(say_hello)

Finally, we show the button and start the Qt main loop:

# Show the button
button.show()
# Run the main Qt loop
app.exec_()

Full Code

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

import sys                                                                                          
from PySide2.QtWidgets import QApplication, QPushButton                                                                                                                                                                                                                                                                  
                                                                                                    
def say_hello():                                                                                     
 print("Button clicked, Hello!")                                                                    
                                                                                                    
# Create the Qt Application                                                                         
app = QApplication(sys.argv)                                                                        
# Create a button, connect it and show it                                                           
button = QPushButton("Click me")                                                                    
button.clicked.connect(say_hello)                                                                    
button.show()                                                                                       
# Run the main Qt loop                                                                              
app.exec_()

A button to exit the application

Following the same idea, we can create a a QPushButton that closes the application when clicked.

from PySide2.QtWidgets import QApplication, QPushButton

if __name__ == "__main__":
    # Create a QApplication
    app = QApplication([])

    # Create a button
    button = QPushButton('Exit')

    # Connect the button "clicked" signal to the exit() method
    # that finishes the QApplication
    button.clicked.connect(app.exit)

    button.show()
    app.exec_()

Another example

Take a look of the following code, it follows the same idea previously described but interacting with other python modules

import sys
import random
from PySide2 import QtCore, QtWidgets, QtGui

class MyWidget(QtWidgets.QWidget):
    def __init__(self):
        QtWidgets.QWidget.__init__(self)

        self.hello = ["Hallo Welt", "你好,世界", "Hei maailma",
            "Hola Mundo", "Привет мир"]

        self.button = QtWidgets.QPushButton("Click me!")
        self.text = QtWidgets.QLabel("Hello World")
        self.text.setAlignment(QtCore.Qt.AlignCenter)

        self.layout = QtWidgets.QVBoxLayout()
        self.layout.addWidget(self.text)
        self.layout.addWidget(self.button)
        self.setLayout(self.layout)

        self.button.clicked.connect(self.magic)


    def magic(self):
        self.text.setText(random.choice(self.hello))


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)

    widget = MyWidget()
    widget.show()

    sys.exit(app.exec_())