Summary of the difference between QWidget and QMainWindow in PyQt6

QWidgetandQMainWindowis two commonly used classes in PyQt, which have significant differences in function and purpose. The following is a detailed comparison and description:

1. QWidget

Introduction

• QWidgetIt is the base class for all widgets (controls) in PyQt.
• It is a general widget that can be used as a container (parent window) or as a standalone control.

Features

• Lightweight: only provides basic window features, such as size, position, background, etc.
• High flexibility: freely combined and customized.
• No built-in layout structure: need to add layout manually (such asQVBoxLayoutorQHBoxLayout) and controls.
• Suitable for use as small windows or nested containers: such as dialog boxes, custom controls, auxiliary windows, etc.

Common usage

• Create custom controls.
• As a dialog window (e.g.QDialogInherited fromQWidget）。
• Nested in other widgets for use.

Simple example

from  import QApplication, QWidget, QLabel, QVBoxLayout

app = QApplication([])

# Create a QWidget windowwindow = QWidget()
("QWidget Example")

# Add controllayout = QVBoxLayout()
(QLabel("This is a QWidget"))
(layout)

()
()

2. QMainWindow

Introduction

• QMainWindowis a class for creating main windows, providing advanced features and layout management.
• It isQWidgetSubclass of  inheritedQWidgetfeatures and extends some features specifically for the main window.

Features

• Built-in layout structure:
  • Includes menu bar (QMenuBar), toolbar (QToolBar), status bar (QStatusBar), docking window (QDockWidget) and central widgets.
• Suitable for complex main window applications: suitable as the main interface for applications, supporting multiple sub-window management and advanced layout requirements.
• Supports central widgets:
  • Need to passsetCentralWidget()Method sets the main content area.

Common usage

• Create the main window of the full desktop application.
• Used for versatile and complex user interfaces.

Simple example

from  import QApplication, QMainWindow, QLabel, QStatusBar

app = QApplication([])

# Create a QMainWindow windowwindow = QMainWindow()
("QMainWindow Example")

# Set the central controlcentral_widget = QLabel("This is a QMainWindow")
(central_widget)

# Add status barstatus_bar = QStatusBar()
status_bar.showMessage("This is a status bar")
(status_bar)

()
()

3. Major differences and comparison

4. Select a suggestion

• useQWidget：

  • If your window is a simple dialog or nested child widget.
  • It requires a complete custom layout and does not require advanced features such as menu bars and toolbars.

• useQMainWindow：

  • If your window is the main interface of an application.
  • Built-in menu bar, toolbar, status bar, docking window and other functions are required.

Summarize

QWidgetIt is the basic widget class, used to build all types of widgets;QMainWindowis an advanced window class suitable for use as the main window of an application. Selecting the right class according to specific needs can complete the development tasks more efficiently.

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