import multiprocessing
import sys
def worker_with(lock,f):
with lock:
fs = open(f,"a+")
fs.write('Lock acquired via withn')
fs.close()
def worker_no_with(lock,f):
lock.acquire()
try:
fs = open(f,"a+")
fs.write('Lock acquired directlyn')
fs.close()
finally:
lock.release()
if __name__ == "__main__":
f = "file.txt"
lock = multiprocessing.Lock()
w = multiprocessing.Process(target=worker_with,args=(lock,f))
nw = multiprocessing.Process(target=worker_no_with,f))
w.start()
nw.start()
w.join()
nw.join()
import multiprocessing
import time
def worker(s,i):
s.acquire()
print(multiprocessing.current_process().name + " acquire")
time.sleep(i)
print(multiprocessing.current_process().name + " release")
s.release()
if __name__ == "__main__":
s = multiprocessing.Semaphore(2)
for i in range(5):
p = multiprocessing.Process(target=worker,args=(s,i*2))
p.start()
import multiprocessing
import time
def wait_for_event(e):
"""Wait for the event to be set before doing anything"""
print ('wait_for_event: starting')
e.wait()
print ('wait_for_event: e.is_set()->' + str(e.is_set()))
def wait_for_event_timeout(e,t):
"""Wait t seconds and then timeout"""
print ('wait_for_event_timeout: starting')
e.wait(t)
print ('wait_for_event_timeout: e.is_set()->' + str(e.is_set()))
if __name__ == '__main__':
e = multiprocessing.Event()
w1 = multiprocessing.Process(name='block',
target=wait_for_event,
args=(e,))
w1.start()
w2 = multiprocessing.Process(name='non-block',
target=wait_for_event_timeout,2))
w2.start()
time.sleep(3)
e.set()
print ('main: event is set')
#the output is:
#wait_for_event_timeout: starting
#wait_for_event: starting
#wait_for_event_timeout: e.is_set()->False
#main: event is set
#wait_for_event: e.is_set()->True
