python threading关于锁的内容

锁：

import threading,time
def addNum():
    global num
    lock.acquire()     #获取锁
    temp=num
    time.sleep(0.01)
    # print('ok')
    num=temp-1
    lock.release()  #释放锁
#锁保证线程没有执行完CPU不会执行别的线程
num=100
lst_Thread=[]
lock=threading.Lock()   #实例锁对象
for i in range(100):
    t=threading.Thread(target=addNum)
    t.start()
    lst_Thread.append(t)
for t in lst_Thread:    #等到所有线程执行完毕，在执行主线程
    t.join()
print('num:',num)

递归锁：

import time,threading
class Account:
    def __init__(self,_id,balance):
        self.id=_id
        self.balance=balance
        # 每一个用户都有自己的一个锁，保证数据安全性
        self.lock=threading.RLock() #递归锁
    def withdraw(self,amount):  #取钱
        with self.lock:
            self.balance-=amount
        # 相当于
        # self.lock.acquire()
        # self.balance -= amount
        # self.lock.release()
    def deposit(self,amount):  #存钱
        with self.lock:
            self.balance+=amount
    def drawcash(self,amount):  #在算过利息后提钱
        with self.lock:
            interest=0.05
            count=amount+amount*interest
            # lock.acquire中嵌套lock.acquire
            self.withdraw(count)
def transfer(_from,to,amount):  #不同账户之间转钱
    #锁不能在这，因为如果别的操作在对balance进行操作的时候，数据不安全
    _from.withdraw(amount)
    to.deposit(amount)
a=Account('001',1000)
b=Account('002',500)
t1=threading.Thread(target=transfer(a,b,100))
t1.start()
t2=threading.Thread(target=transfer(b,a,150))
t2.start()
t1.join()
t2.join()
print(a.balance)
print(b.balance)