example-code-2e/18b-async-await/spinner_thread.py

52 lines
1.2 KiB
Python

# spinner_thread.py
# credits: Adapted from Michele Simionato's
# multiprocessing example in the python-list:
# https://mail.python.org/pipermail/python-list/2009-February/538048.html
# BEGIN SPINNER_THREAD
import threading
import itertools
import time
import sys
def spin(msg, done): # <2>
write, flush = sys.stdout.write, sys.stdout.flush
for char in itertools.cycle('|/-\\'): # <3>
status = char + ' ' + msg
write(status)
flush()
write('\x08' * len(status)) # <4>
if done.wait(.1): # <5>
break
write(' ' * len(status) + '\x08' * len(status)) # <6>
def slow_function(): # <7>
# pretend waiting a long time for I/O
time.sleep(3) # <8>
return 42
def supervisor(): # <9>
done = threading.Event()
spinner = threading.Thread(target=spin,
args=('thinking!', done))
print('spinner object:', spinner) # <10>
spinner.start() # <11>
result = slow_function() # <12>
done.set() # <13>
spinner.join() # <14>
return result
def main():
result = supervisor() # <15>
print('Answer:', result)
if __name__ == '__main__':
main()
# END SPINNER_THREAD