Use join for thread synchronization in python
tags: python notes Multithreading python
import threading
import time
lock = threading.Lock()
threads = []
class MyThread(threading.Thread):
def __init__(self, threadID, name, counter):
threading.Thread.__init__(self)
self.threadID = threadID
self.name = name
self.counter = counter
def run(self):
print("Start thread" + self.name)
lock.acquire()
# Open lock
print_time(self.name, self.counter, 3)
# Release the lock
lock.release()
def print_time(ThreadName, delay, counter):
while counter:
time.sleep(delay)
print("%s : %s " % (ThreadName, time.ctime(time.time())))
counter -= 1
def _main():
# Create thread
thread1 = MyThread(1, "Thread-1", 1)
thread2 = MyThread(2, "Thread-2", 2)
thread1.start()
thread2.start()
print('Exit the main thread')
When executing the above program, you will find that after the main thread exits, the child threads are still executing, and the process ends after all the child threads are executed.
threads.append(thread1)
threads.append(thread2)
for i in threads:
i.join()
print('Exit the main thread')
Insert join() after start to achieve thread synchronization, so that the main thread can enter the blocking state before the execution of the child thread is completed. After the execution of the child thread is completed, the main thread will continue to execute.
The output result becomes
Start thread Thread-1
Start thread Thread-2
…(sub-thread printing result)
Exit the main thread
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