Summarised from: https://www.pythonguis.com/tutorials/pyside6-creating-your-first-window/

Simple Window

from PySide6.QtWidgets import QApplication, QWidget

# Only needed for access to command line arguments
import sys

# You need one (and only one) QApplication instance per application.
# Pass in sys.argv to allow command line arguments for your app.
# If you know you won't use command line arguments QApplication([]) works too.
app = QApplication(sys.argv)

# Create a Qt widget, which will be our window.
window = QWidget()
window.show()  # IMPORTANT!!!!! Windows are hidden by default.

# Start the event loop.
app.exec_()

Any Widget Can Be a Window

import sys
from PySide6.QtWidgets import QApplication, QPushButton

app = QApplication(sys.argv)

window = QPushButton("Push Me")
window.show()

app.exec_()

Subclassing QMainWindow

import sys

from PySide6.QtCore import QSize, Qt
from PySide6.QtWidgets import QApplication, QMainWindow, QPushButton


# Subclass QMainWindow to customize your application's main window
class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()

        self.setWindowTitle("My App")

        button = QPushButton("Press Me!")

        # Set the central widget of the Window.
        self.setCentralWidget(button)


app = QApplication(sys.argv)

window = MainWindow()
window.show()

app.exec_()

Sizing Widgets

import sys

from PySide6.QtCore import QSize, Qt
from PySide6.QtWidgets import QApplication, QMainWindow, QPushButton


# Subclass QMainWindow to customize your application's main window
class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()

        self.setWindowTitle("My App")

        button = QPushButton("Press Me!")

        self.setFixedSize(QSize(400, 300))

        # Set the central widget of the Window.
        self.setCentralWidget(button)


app = QApplication(sys.argv)

window = MainWindow()
window.show()

app.exec_()

Signals and Slots

Push Button

iort sys
from PySide6.QtWidgets import QApplication, QMainWindow, QPushButton


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

        self.setWindowTitle("My App")

        button = QPushButton("Press Me!")
        button.setCheckable(True)
        button.clicked.connect(self.the_button_was_clicked)

        # Set the central widget of the Window.
        self.setCentralWidget(button)

    def the_button_was_clicked(self):
        print("Clicked!")


app = QApplication(sys.argv)

window = MainWindow()
window.show()

app.exec_()

Buttons Can Be Checkable and Signals Can Carry Data

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

        self.setWindowTitle("My App")

        button = QPushButton("Press Me!")
        button.setCheckable(True)
        button.clicked.connect(self.the_button_was_clicked)
        button.clicked.connect(self.the_button_was_toggled)

        self.setCentralWidget(button)

    def the_button_was_clicked(self):
        print("Clicked!")

    def the_button_was_toggled(self, checked):
        print("Checked?", checked)

Retrieving State of a Widget

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

        self.button_is_checked = True

        self.setWindowTitle("My App")

        self.button = QPushButton("Press Me!")
        self.button.setCheckable(True)
        self.button.released.connect(self.the_button_was_released)
        self.button.setChecked(self.button_is_checked)

        self.setCentralWidget(self.button)

    def the_button_was_released(self):
        self.button_is_checked = self.button.isChecked()

        print(self.button_is_checked)

Changing Properties of Widgets

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

        self.setWindowTitle("My App")

        self.button = QPushButton("Press Me!")
        self.button.clicked.connect(self.the_button_was_clicked)

        self.setCentralWidget(self.button)

    def the_button_was_clicked(self):
        self.button.setText("You already clicked me.")
        self.button.setEnabled(False)

        # Also change the window title.
        self.setWindowTitle("My Oneshot App")

Changing Window Titles

from PySide6.QtWidgets import QApplication, QMainWindow, QPushButton

import sys
from random import choice

window_titles = [
    'My App',
    'My App',
    'Still My App',
    'Still My App',
    'What on earth',
    'What on earth',
    'This is surprising',
    'This is surprising',
    'Something went wrong'
]


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

        self.n_times_clicked = 0

        self.setWindowTitle("My App")

        self.button = QPushButton("Press Me!")
        self.button.clicked.connect(self.the_button_was_clicked)

        self.windowTitleChanged.connect(self.the_window_title_changed)

        self.setCentralWidget(self.button)

    def the_button_was_clicked(self):
        print("Clicked.")
        new_window_title = choice(window_titles)
        print("Setting title:  %s" % new_window_title)
        self.setWindowTitle(new_window_title)

    def the_window_title_changed(self, window_title):
        print("Window title changed: %s" % window_title)

        if window_title == 'Something went wrong':
            self.button.setDisabled(True)


app = QApplication(sys.argv)

window = MainWindow()
window.show()

app.exec_()