PySide6 Crash Course: GUI Development in Python with Qt6

PySide 6 Crash Course Summary

Key Concepts:

• PySide 6: A Python package for developing GUI applications using the Qt 6 framework.
• PyQt6: An alternative Python package for Qt 6 GUI development; functionally similar to PySide 6 but with potential licensing differences.
• Qt Widgets: UI elements like buttons, labels, text boxes, etc., provided by the Qt framework.
• Layouts: Mechanisms (e.g., QVBoxLayout, QHBoxLayout, QGridLayout) for arranging widgets within a window.
• Events: Actions triggered by user interaction (e.g., button clicks, item selection) that can be connected to functions.
• Qt Designer: A graphical tool for designing UI layouts visually.
• QApplication: The overall application instance.
• QMainWindow: The main window of the application.
• QUiLoader: A class used to load UI designs created in Qt Designer.

1. Introduction and Setup

• The video provides a crash course on PySide 6 for developing modern GUI applications in Python.
• It addresses the choice between PySide 6 and PyQt6, noting that the functional differences are minimal, with licensing being the primary consideration.
• The tutorial focuses on PySide 6.
• The presenter emphasizes the importance of the Qt documentation for exploring components not covered in the video. The documentation can be found at the link in the description. It includes modules API, QT modules supported by QT for Python, and QT widgets.
• Setup involves installing PySide 6 using pip install pyside6 (or pip3 install pyside6). Virtual environments are recommended. The presenter uses UV, but pip is the standard approach.

2. Basic "Hello World" Application

• A minimal "Hello World" application is created to demonstrate the fundamental structure.
• Key components:
  • QApplication: The application instance.
  • QMainWindow: The main window.
  • QLabel: A text label.
• Code example:

  from PySide6.QtWidgets import QApplication, QMainWindow, QLabel
  from PySide6.QtCore import Qt
  
  class MainWindow(QMainWindow):
      def __init__(self):
          super().__init__()
          self.setWindowTitle("Hello World Application")
          label = QLabel("Hello World")
          label.setAlignment(Qt.AlignCenter)
          self.setCentralWidget(label)
  
  app = QApplication([])
  window = MainWindow()
  window.show()
  app.exec()
  

• label.setAlignment(Qt.AlignCenter) centers the label.
• self.setCentralWidget(label) sets the label as the main content of the window.
• app.exec() starts the application event loop.

3. Layouts and Multiple Widgets

• To display multiple widgets, layouts are necessary.
• Key layout classes:
  • QVBoxLayout: Arranges widgets vertically.
  • QHBoxLayout: Arranges widgets horizontally.
  • QGridLayout: Arranges widgets in a grid.
• A QWidget acts as a container for other widgets.
• Example: Using QVBoxLayout to stack labels vertically:

  from PySide6.QtWidgets import QApplication, QMainWindow, QLabel, QWidget, QVBoxLayout
  from PySide6.QtCore import Qt
  
  class MainWindow(QMainWindow):
      def __init__(self):
          super().__init__()
          self.setWindowTitle("Layout Example")
          container = QWidget()
          layout = QVBoxLayout(container)
  
          label1 = QLabel("One")
          label1.setAlignment(Qt.AlignCenter)
          label2 = QLabel("Two")
          label2.setAlignment(Qt.AlignCenter)
          label3 = QLabel("Three")
          label3.setAlignment(Qt.AlignCenter)
          label4 = QLabel("Four")
          label4.setAlignment(Qt.AlignCenter)
  
          layout.addWidget(label1)
          layout.addWidget(label2)
          layout.addWidget(label3)
          layout.addWidget(label4)
  
          self.setCentralWidget(container)
  
  app = QApplication([])
  window = MainWindow()
  window.show()
  app.exec()
  

• For QGridLayout, the addWidget method requires row and column indices: layout.addWidget(label1, 0, 0).

4. Different Widget Types

• Various widget types are introduced:
  • QPushButton: A clickable button.
  • QLineEdit: A single-line text input field.
  • QTextEdit: A multi-line text input area.
  • QComboBox: A drop-down selection box.
  • QListWidget: A list of selectable items.
  • QCheckBox: A checkable box.
  • QRadioButton: A radio button (mutually exclusive selection).
  • QSlider: A slider control.
• Example: Adding a button and a line edit:

  from PySide6.QtWidgets import QApplication, QMainWindow, QLabel, QWidget, QVBoxLayout, QPushButton, QLineEdit
  from PySide6.QtCore import Qt
  
  class MainWindow(QMainWindow):
      def __init__(self):
          super().__init__()
          self.setWindowTitle("Widget Example")
          container = QWidget()
          layout = QVBoxLayout(container)
  
          label = QLabel("Enter Text:")
          layout.addWidget(label)
  
          line_edit = QLineEdit()
          layout.addWidget(line_edit)
  
          button = QPushButton("Click Me")
          layout.addWidget(button)
  
          self.setCentralWidget(container)
  
  app = QApplication([])
  window = MainWindow()
  window.show()
  app.exec()
  

• Widgets can be nested within containers and layouts for complex UI structures.

5. Adding Functionality with Events

• Events are signals emitted by widgets in response to user actions.
• Common events:
  • clicked: Triggered when a button is clicked.
  • toggled: Triggered when a radio button's state changes.
  • itemClicked: Triggered when an item in a list widget is clicked.
  • itemDoubleClicked: Triggered when an item in a list widget is double-clicked.
• The connect method associates an event with a function (or lambda expression).
• Example: Connecting a button click to a lambda function:

  button.clicked.connect(lambda: print("Button Clicked!"))
  

• Example: Connecting radio button toggling to a function:

  def radio_changed(self):
      sender = self.sender()
      if sender.isChecked():
          print(f"Radio button was selected value {sender.text()}")
  
  for r in [radio1, radio2, radio3]:
      r.toggled.connect(self.radio_changed)
  

• The self.sender() method identifies the widget that emitted the signal.

6. Menu Bars

• Menu bars provide a traditional application menu structure (File, Edit, Help, etc.).
• Access the menu bar using self.menuBar().
• Add menus using menuBar.addMenu("File").
• Add actions to menus using file_menu.addAction("Exit").
• Connect actions to functions using exit_action.triggered.connect(self.close).
• Example:

  file_menu = self.menuBar().addMenu("File")
  exit_action = file_menu.addAction("Exit")
  exit_action.triggered.connect(self.close)
  

7. Message Boxes

• Message boxes display dialogs to the user.
• QMessageBox.information(self, "Info", "Hello World") displays a simple informational message.
• QMessageBox.question(self, "Question", "Do you like Python?") displays a question with Yes/No buttons.
• Custom message boxes can be created by instantiating QMessageBox, adding buttons, and handling the button clicks.
• Example:

  msg = QMessageBox(self)
  msg.setWindowTitle("Choice")
  msg.setText("Select your favorite programming language")
  python_button = msg.addButton("Python", QMessageBox.AcceptRole)
  cpp_button = msg.addButton("C++", QMessageBox.RejectRole)
  java_button = msg.addButton("Java", QMessageBox.DestructiveRole)
  
  msg.exec()
  
  if msg.clickedButton() == python_button:
      print("User's favorite language is Python")
  elif msg.clickedButton() == cpp_button:
      print("User's favorite language is C++")
  else:
      print("User's favorite language is Java")
  

8. Secondary Windows

• Multiple windows can be created in a single application.
• Create a new class inheriting from QMainWindow for each window type.
• Keep track of open windows using a list.
• Example:

  class SecondaryWindow(QMainWindow):
      def __init__(self, n):
          super().__init__()
          self.setWindowTitle(f"Window Number {n}")
          label = QLabel(f"Number {n}")
          label.setAlignment(Qt.AlignCenter)
          self.setCentralWidget(label)
  
  def open_window(self):
      self.count += 1
      w = SecondaryWindow(self.count)
      self.windows.append(w)
      w.show()
  

9. Qt Designer Integration

• Qt Designer allows visual design of UIs.
• Save the UI design as a .ui file.
• Use QUiLoader to load the UI file into Python.
• Access widgets by their object names (defined in Qt Designer).
• Example:

  from PySide6.QtWidgets import QApplication, QMessageBox
  from PySide6.QtCore import QFile
  from PySide6.QtUiTools import QUiLoader
  
  app = QApplication([])
  
  loader = QUiLoader()
  file = QFile("gui.ui")
  file.open(QFile.ReadOnly)
  window = loader.load(file)
  file.close()
  
  window.pushButton.clicked.connect(lambda: QMessageBox.information(window, "Message", window.lineEdit.text()))
  
  window.show()
  app.exec()
  

• window.pushButton and window.lineEdit refer to the button and line edit widgets defined in the .ui file.

10. Conclusion

• The crash course covers the fundamentals of PySide 6 GUI development.
• Key takeaways:
  • Understanding Qt widgets and layouts.
  • Handling events to add functionality.
  • Using Qt Designer for visual UI design.
• The presenter encourages viewers to explore the Qt documentation for more advanced features and widgets.
• The presenter asks for feedback on interest in more in-depth PySide 6 tutorials, PyQt6, or other GUI frameworks.

Notable Quotes:

• "The only difference is in licensing. So maybe you want to take a look at both licenses. The PIQT6 license seems to be a little bit more problematic or restrictive."
• "I'm just going to get you started with the package. So you know how it works, you know how to use it, you know how to build applications, and then you can go deeper on your own and explore more exotic components that you want to add to your applications."
• "Each component has different settings. For combo box and list widget, you have to add items. For the slider, you set the range and so on. Depending on what you're using, you will have to set up different things. But the idea is you just add them as widgets to your layouts."
• "You basically have an UI element. You have events that you can listen to. You connect these and then you just connect them to a function that is either defined inline here like a lambda expression but more likely you're going to use something like this where you define a complex function like opening a new v window or closing the application or connecting to a database or something but you do that as a reaction of an event which is clicked item clicked item doubleclicked toggled or anything else."