python基础一 day40 线程锁 信号量 事件

锁：
import time
from threading import Lock,Thread
# Lock 互斥锁
# 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‘,args=(‘nezha‘,)).start()

from threading import RLock   # 递归锁
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‘,args=(‘nezha‘,)).start()

import time
from threading import Semaphore,Thread
def func(sem,a,b):
    sem.acquire()
    time.sleep(1)
    print(a+b)
    sem.release()

sem = Semaphore(4)
for i in range(10):
    t = Thread(target=func,args=(sem,i,i+5))
    t.start()

import time
import random
from threading import Thread,Event
def connect_db(e):
    count = 0
    while count < 3:
        e.wait(0.5)   # 状态为False的时候,我只等待1s就结束
        if e.is_set() == True:
            print(‘连接数据库‘)
            break
        else:
            count += 1
            print(‘第%s次连接失败‘%count)
    else:
        raise TimeoutError(‘数据库连接超时‘)

def check_web(e):
    time.sleep(random.randint(0,3))
    e.set()

e = Event()
t1 = Thread(target=connect_db,args=(e,))
t2 = Thread(target=check_web,))
t1.start()
t2.start()