Python多线程同步互斥机制与死锁原理详解

from threading import Event
e = Event() 创建线程event对象
e.wait([timeout]) 阻塞等待e被set
e.set() 设置e，使wait结束阻塞
e.clear() 使e回到未被设置状态
e.is_set() 查看当前e是否被设置

import time
import threading
 
event = threading.Event()
 
 
# 红绿灯
def lighter():
  count = 0
  event.set() # 刚进来的时候是绿灯
  while True:
    if 4 < count < 10:
      event.clear() # 清除设置，阻塞等待
      print("[信号灯]：红，不能通行", count)
    elif count >= 10: # 添加设置，继续执行
      event.set()
      count = 0
    else:
      event.set() # 添加设置，继续执行
      print("[信号灯]：绿灯，可以通行", count)
    time.sleep(1)
    count += 1
 
 
# 汽车
def car(name):
  while True:
    if event.is_set():
      print("{0}: 绿灯 , 走起...".format(name))
      time.sleep(1)
    else:
      print("{0}: 红灯 , 停车...".format(name))
      event.wait()
      print("{0}: 绿灯亮了 , 继续前进...".format(name))
 
 
light = threading.Thread(target=lighter, )
light.start()
car1 = threading.Thread(target=car, args=("小跑",))
car1.start()

from threading import Lock
lock = Lock() #创建锁对象
lock.acquire() #上锁 如果lock已经上锁再调用会阻塞
lock.release() #解锁

from threading import Thread, Lock
from time import sleep
 
a = b = 0
lock = Lock()
 
 
# 子线程输出a b
def value():
  while True:
    lock.acquire() # 上锁
    if a != b:
      print("a = %d,b = %d" % (a, b))
    lock.release() # 解锁
 
 
t = Thread(target=value)
t.start()
 
# 主线程加锁更改a b时候，子线程处理a b 时也要进行加锁，重复加锁就会阻塞等待主线程处理结束
# 同理主进程再次更改a b 时等 子进程结束才可以
while True:
  with lock: # 自动上/解锁
    a += 1
    b += 1
t.join

from threading import Lock, Thread
 
 
# 交易类
class Account:
  def __init__(self, _id, balance, lock):
    self.id = _id
    self.balance = balance
    self.lock = lock # 各自账户锁
 
  # 取钱
  def withdraw(self, amount):
    self.balance -= amount
 
  # 存钱
  def deposit(self, amount):
    self.balance += amount
 
  # 查看账户
  def get_balance(self):
    return self.balance
 
 
# 转账
def transfer(from_, to, amount):
  if from_.lock.acquire(): # 锁住自己的账户
    from_.withdraw(amount) # 自己账户减少
    if to.lock.acquire(): # 锁住对方账户
      to.deposit(amount) # 对方账户增加
      to.lock.release() # 解锁对方账户
    from_.lock.release() # 自己账户解锁
  print("转账完成")
 
 
Abby = Account("Abby", 5000, Lock())
Balen = Account("Balen", 3000, Lock())
 
t = Thread(target=transfer, args=(Abby, Balen, 1000))
t2 = Thread(target=transfer, args=(Balen, Abby, 500))
t.start()
t2.start()
t.join()
t2.join()
 
print("Abby:", Abby.get_balance())
print("Balen:", Balen.get_balance())