Spinner threading

spinner_thread.py

import sys
import threading

class Signal:
	stop = False

def spin(signal):
	write, flush = sys.stdout.write, sys.stdout.flush  # create alias
	for char in itertools.cycle('|/-\\'):
		msg = char + ' loading ...'
		write(msg)
		flush()
		write('\x08' * len(msg))  # use char \x08 to move cursor back
		time.sleep(.1)  # control spin rate
		if signal.stop:
			break
	# use space to clear line and move cursor to head
	write(' ' * len(msg) + '\x08' * len(msg))
	
def slow_func():
	time.sleep(5)  # blocking I/O
	return True
	
signal = Signal()
spinner = threading.Thread(target=spin, args=(signal,))

spinner.start()  # start spinner thread
result = slow_func()  # main thread blocked here

# slow_func done, trigger spinner thread to stop
signal.stop = True
spinner.join()  # wait until finish

print(f'Result: {result}')