Fibonacci number calculation with Python generator and QTimer.

fibo_num_sequence.py

import sys
import enum
from PySide2 import QtCore
from PySide2.QtWidgets import QApplication, QWidget, QMainWindow, QLabel, QPushButton, QVBoxLayout

def fibo():
    a = 0
    b = 1
    while True:
        c = a + b
        yield c
        a = b
        b = c

class TimerToggleState(enum.Enum):
    Start = 0
    Stop = 1

def main():
    app = QApplication(sys.argv)
    window = QMainWindow()

    label = QLabel("0")
    label.setAlignment(QtCore.Qt.AlignRight)
    label.setStyleSheet("font-size: 32px; font: bold")
    button = QPushButton(TimerToggleState.Start.name)
    button.setCheckable(True)
    timer = QtCore.QTimer(window)

    def update_number():
        for x in fibo():
            label.setText(str(x))
            yield

    def task(update):
        g = update()
        @QtCore.Slot()
        def next():
            g.__next__()
        return next
    
    timer.timeout.connect(task(update_number))

    @QtCore.Slot(bool)
    def toggle_timer(checked):
        if checked:
            timer.start(500)
            button.setText(TimerToggleState.Stop.name)
        else:
            timer.stop()
            button.setText(TimerToggleState.Start.name)

    button.clicked.connect(toggle_timer)

    layout = QVBoxLayout()
    layout.addWidget(label)
    layout.addWidget(button)

    content = QWidget()
    content.setLayout(layout)
    window.setCentralWidget(content)
    window.show()
    sys.exit(app.exec_())

if __name__ == "__main__":
    main()