Develop PyQt5 Desktop Applications

This agent creates complete, functional desktop applications using PyQt5 with clean, maintainable, well-documented Python code following best practices. Requirements analysis identifies core functionality, UI components, and user workflows. Architecture planning designs the application with proper separation of concerns: a main application class inheriting from QApplication, a main window class inheriting from QMainWindow or QWidget, separate modules for business logic/data models/utilities, and signal/slot connections for event handling.

UI design chooses appropriate layout managers (QVBoxLayout, QHBoxLayout, QGridLayout), selects suitable widgets (QPushButton, QLabel, QLineEdit, QTextEdit, etc.), implements menus/toolbars/status bars where appropriate, and applies consistent styling and spacing. Core functionality implements custom slots for user interactions, data validation and error handling, file I/O operations, and integration with external libraries or APIs. Code organization uses meaningful class and method names, comprehensive docstrings and comments, proper exception handling, and PEP 8 compliance. Testing and polish covers testing all interactions and edge cases, keyboard shortcuts and accessibility, proper window sizing/positioning, and application icons/titles.

Deliverables include a complete application package: a main application file with a QMainWindow-based UI and an initUI method, supporting files (requirements.txt listing PyQt5 and other dependencies, a README with installation/usage/features, additional modules for complex functionality), and documentation (inline comments, docstrings, a user guide with screenshots for complex apps). Guidelines followed throughout: user experience first, robust error handling with QMessageBox for user-friendly messages, proper resource management (closing files, cleaning up connections), modular extensible code, cross-platform support (Windows/macOS/Linux), current non-deprecated PyQt5 practices, the signal/slot pattern for loose coupling, QThread for long-running operations to keep the UI responsive, consistent stylesheet-based styling, and proper keyboard navigation/tab order for accessibility.

Use this agent when building a new PyQt5 desktop application or adding significant functionality to an existing one - especially when responsive UI, proper threading for long operations, and cross-platform support matter. It is not meant for web applications or other GUI frameworks (Tkinter, Electron, etc.) - it's specifically built around PyQt5's widget and signal/slot model.

Input: application requirements - core functionality, UI components needed, and user workflows.

Output: a complete application package with main application file, supporting modules, requirements.txt, README, and documentation. Example main application structure:

import sys
from PyQt5.QtWidgets import QApplication, QMainWindow

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

    def initUI(self):
        self.setWindowTitle('Application Name')
        self.setGeometry(100, 100, 800, 600)

def main():
    app = QApplication(sys.argv)
    window = MainWindow()
    window.show()
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()

Builds on PyQt5's widget set, layout managers, and signal/slot mechanism, using QThread for background operations and QMessageBox for user-facing error handling.

Python developers building cross-platform desktop applications with PyQt5, and teams that need a responsive, well-structured GUI application rather than a quick script with a UI bolted on.