线程--守护线程、线程锁、信号量、事件、条件、定时器、队列、池（三）

守护线程

import time
from threading import Thread
def func1():
    while True:
 print('*'*10)
 time.sleep(1)
def func2():
 print('in func2')
 time.sleep(5)

t = Thread(target=func1,)
t.daemon = True
t.start()
t2 = Thread(target=func2,)
t2.start()
t2.join() #加join后会等待func2结束后在打印
print('主线程')

# 守护进程随着主进程代码的执行结束而结束 
# 守护线程会在主线程结束之后等待其他子线程的结束才结束 

# 主进程在执行完自己的代码之后不会立即结束 而是等待子进程结束之后 回收子进程的资源
# import time
# from multiprocessing import Process
# def func():
# time.sleep(5)
#
# if __name__ == '__main__':
# Process(target=func).start()

线程锁

为什么Cpython自带GIL锁还出现死锁，因为是对线程GIL锁，避免不了时间片轮转带来数据不安全

 

import time
from threading import Lock,Thread
# Lock 互斥锁（只有一个钥匙） 
# def func(lock):
# global n
# lock.acquire()
# temp = n
# time.sleep(0.2)
# n = temp - 1
# lock.release()
#
# n = 10
# t_lst = []
# lock = Lock()
# for i in range(10):
# t = Thread(target=func,args=(lock,))
# t.start()
# t_lst.append(t)

# for t in t_lst: t.join()
# print(n)



# 科学家吃面

# noodle_lock = Lock()
# fork_lock = Lock()
# def eat1(name):
# noodle_lock.acquire()
# print('%s拿到面条啦'%name)
# fork_lock.acquire()
# print('%s拿到叉子了'%name)
# print('%s吃面'%name)
# fork_lock.release()
# noodle_lock.release()
#
# def eat2(name):
# fork_lock.acquire()
# print('%s拿到叉子了'%name)
# time.sleep(1)
# noodle_lock.acquire()
# print('%s拿到面条啦'%name)
# print('%s吃面'%name)
# noodle_lock.release()
# fork_lock.release()
#
# Thread(target=eat1,args=('alex',)).start() 
# Thread(target=eat2,args=('Egon',)).start()
# Thread(target=eat1,args=('bossjin',)).start()
# Thread(target=eat2,args=('nezha',)).start()
执行上面代码后出现死锁阻塞








解决死锁问题


from threading import RLock # 递归锁（一串钥匙，多少根据accquire多少次） 
fork_lock = noodle_lock = RLock() # 一个钥匙串上的两把钥匙
def eat1(name):
 noodle_lock.acquire() # 一把钥匙
 print('%s拿到面条啦'%name)
 fork_lock.acquire()
 print('%s拿到叉子了'%name)
 print('%s吃面'%name)
 fork_lock.release()
 noodle_lock.release()

def eat2(name):
 fork_lock.acquire()
 print('%s拿到叉子了'%name)
 time.sleep(1)
 noodle_lock.acquire()
 print('%s拿到面条啦'%name)
 print('%s吃面'%name)
 noodle_lock.release()
 fork_lock.release()

Thread(target=eat1,args=('alex',)).start()
Thread(target=eat2,args=('Egon',)).start()
Thread(target=eat1,args=('bossjin',)).start()
Thread(target=eat2,args=('nezha',)).start()