Context Manager thread safe

Question

With that code I am hoping, that it should print "enter" right away, then sleep, then print "exit". But it does it all in one go. How would I get it to work? And right now its locking the main application, so ideally I want to run the called function in a separate thread. But then "enter" and "exit" are printed immediately, and after the sleep timer the function call.

import time

def test_run():
   time.sleep(1)


class Update(object):
   def __init__(self):
       pass
   def __enter__(self):
       print 'enter'
   def __exit__(self, *_):
       print 'exit'

with Update():
   test_run()

Answer 1

Your code works for me.

import time
import threading

def test_run():    
    time.sleep(5)

def run_update():
    with Update():
        test_run()

class Update(object):
    def __init__(self):
        pass
    def __enter__(self):
        print('enter')
    def __exit__(self, *_):
        print('exit')

if __name__ == "__main__":
    th = threading.Thread(target=run_update)
    th.start()
    for i in range(100):
        print(i)

If you increase the sleep time it might be more noticeable.