标签:之间 def war sub() tar 线程锁 强制 赋值 star
from threading import Thread
n = 0
def add():
for i in range(500000):
global n
n += 1
def sub():
for i in range(500000):
global n
n -= 1
t_l = []
for i in range(2):
t1 = Thread(target=add)
t1.start()
t2 = Thread(target=sub)
t2.start()
t_l.append(t1)
t_l.append(t2)
for t in t_l:
t.join()
print(n)
#结果n不为0
from threading import Thread
import time
n = []
def append():
for i in range(500000):
n.append(1)
def pop():
for i in range(500000):
if not n:
time.sleep(0.0000001)
n.pop()
t_l = []
for i in range(20):
t1 = Thread(target=append)
t1.start()
t2 = Thread(target=pop)
t2.start()
t_l.append(t1)
t_l.append(t2)
for t in t_l:
t.join()
print(n)
#使用append pop方法数据安全
+= -= *= /= while if 数据不安全 + 和 赋值是分开的两个操作
append pop strip数据安全 列表中的方法或者字典中的方法去操作全局变量的时候 数据安全的
线程之间也存在数据不安全
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)
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)
不要操作全局变量,不要在类里操作静态变量
+= -= *= /= if while 数据不安全
queue logging 数据安全的
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()
标签:之间 def war sub() tar 线程锁 强制 赋值 star
原文地址:https://www.cnblogs.com/wyh0717/p/13379849.html