PyQt5 GUI Tutorial: Create Python Desktop Apps Step by Step

What is PyQt5 and Why Use It?

PyQt5 is a set of Python bindings for the Qt library — one of the most powerful tools for building cross-platform graphical user interfaces. With PyQt5, developers can create professional desktop applications featuring modern design and rich functionality.

Key Features of PyQt5

PyQt5 offers a wide range of capabilities:

• A vast collection of ready-to-use widgets via the QtWidgets module
• Full support for windows, buttons, input fields, and lists
• Signal and slot mechanism for event-driven programming
• Integration with graphical elements through QGraphicsView
• Customizable interfaces using stylesheets
• Cross-platform compatibility across major operating systems

Installing PyQt5

Install PyQt5 using pip:

pip install PyQt5

Creating Your First Application Window

Every PyQt5 application starts with creating a QApplication object. This is the main application object that manages all windows and events. The main window is built on QWidget.

import sys
from PyQt5.QtWidgets import QApplication, QWidget

app = QApplication(sys.argv)
window = QWidget()
window.setWindowTitle("Simple Window")
window.resize(300, 200)
window.show()
sys.exit(app.exec_())

QApplication is mandatory for any PyQt5 GUI application. It handles system events and manages the application lifecycle.

Working with Core UI Controls

QLineEdit - Text Input Field

QLineEdit is a single-line text input field. This widget is widely used to capture user input.

from PyQt5.QtWidgets import QLineEdit, QVBoxLayout, QPushButton

window = QWidget()
window.setWindowTitle("QLineEdit Example")

layout = QVBoxLayout()

line_edit = QLineEdit()
line_edit.setPlaceholderText("Enter your name")

button = QPushButton("Submit")

def on_click():
    print(f"Hello, {line_edit.text()}!")

button.clicked.connect(on_click)

layout.addWidget(line_edit)
layout.addWidget(button)
window.setLayout(layout)
window.show()

The input field supports various methods for text manipulation:

• setText() - programmatically set text
• text() - retrieve the entered text
• setPlaceholderText() - set placeholder text
• setMaxLength() - limit maximum input length

QComboBox - Creating Dropdown Lists

QComboBox lets users select one option from a dropdown list.

from PyQt5.QtWidgets import QComboBox

combo = QComboBox()
combo.addItems(["Select an option", "Python", "C++", "JavaScript"])

def on_selection_change(value):
    print(f"You selected: {value}")

combo.currentTextChanged.connect(on_selection_change)

layout.addWidget(combo)

QComboBox provides several useful methods:

• addItem() - add a single item
• addItems() - add a list of items
• currentText() - get the currently selected text
• currentIndex() - get the index of the selected item
• clear() - remove all items

QCheckBox - Working with Checkboxes and Signals

QCheckBox allows users to toggle an option on or off.

from PyQt5.QtWidgets import QCheckBox

checkbox = QCheckBox("I agree to the terms")

def on_checkbox_state(state):
    if state:
        print("Checkbox is checked")
    else:
        print("Checkbox is unchecked")

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