python 进程 线程

进程引包multiprocessing，进程是资源最小单位，每个进程拥有自己的资源，不涉及资源互斥

线程引包threading，线程是是cpu调度的最小单位，可以访问共享资源，使用互斥锁对共享资源加锁

import threading
import multiprocessing
import time

count = 0
mutex = threading.Lock()

def test():
    global count
    mutex.acquire()
    for i in range(100):
        count += 1
        time.sleep(0.02)
    mutex.release()
    print(f"thread is {threading.current_thread()}count is {count}")

def test1():
    global count
    mutex.acquire()
    for i in range(100):
        count += 1
        time.sleep(0.02)
    mutex.release()
    print(f"thread is {threading.current_thread()}count is {count}")


if __name__ == '__main__':
    threading.Thread(target=test).start()
    threading.Thread(target=test1).start()
    # multiprocessing.Process(target=test).start()
    # multiprocessing.Process(target=test).start()

加锁前：原因对count竞争性操作

thread is <Thread(Thread-1, started 5872)>count is 200

thread is <Thread(Thread-2, started 8124)>count is 200

加锁后输出：

thread is <_MainThread(MainThread, started 5960)>count is 100

thread is <_MainThread(MainThread, started 10076)>count is 100