线程锁（Python）

一、多个线程对同一个数据进行修改

from threading import Thread,Lock
n = 0
def add(lock):
    for i in range(500000):
        global n
        with lock:
            n += 1
def sub(lock):
    for i in range(500000):
        global n
        with lock:
            n -= 1

t_l = []
lock = Lock()
for i in range(2):
    t1 = Thread(target=add,args=(lock,))
    t1.start()
    t2 = Thread(target=sub,args=(lock,))
    t2.start()
    t_l.append(t1)
    t_l.append(t2)
for t in t_l:
    t.join()
print(n)

二、多个线程对同一列表进行操作

from threading import Thread,Lock
import time
n = []
def append():
    for i in range(500000):
        n.append(1)
def pop(lock):
    for i in range(500000):
        with lock:
            if not n:
                time.sleep(0.0000001)    # 强制CPU轮转
            n.pop()

t_l = []
lock = Lock()
for i in range(20):
    t1 = Thread(target=append)
    t1.start()
    t2 = Thread(target=pop,args=(lock,))
    t2.start()
    t_l.append(t1)
    t_l.append(t2)
for t in t_l:
    t.join()
print(n)

三、单例模式创建对象加锁

import time
class A:
    from threading import Lock
    __instance = None
    lock = Lock()
    def __new__(cls, *args, **kwargs):
        with cls.lock:
            if not cls.__instance:
                time.sleep(0.000001)   # cpu轮转
                cls.__instance = super().__new__(cls)
        return cls.__instance

def func():
    a = A()
    print(a)
from threading import Thread
for i in range(10):
    Thread(target=func).start()

拓展

#拓展知识（将函数执行过程的底层指令打印出来）
import dis
a = 0
def func():
    global a
    a += 1
print(dis.dis(func))
'''
锁
0 LOAD_GLOBAL
2 LOAD_CONST 
4 INPLACE_ADD
# GIL锁切换了
6 STORE_GLOBAL
释放锁
'''

总结

1：不要操作全局变量,不要在类里操作静态变量
2：+= -= *= /= if while 数据不安全
3：queue logging 数据安全的