淺談Python線程的同步互斥與死鎖

from threading import Event
e = Event() 創(chuàng)建線程event對象
e.wait([timeout]) 阻塞等待e被set
e.set() 設(shè)置e，使wait結(jié)束阻塞
e.clear() 使e回到未被設(shè)置狀態(tài)
e.is_set() 查看當(dāng)前e是否被設(shè)置

import time
import threading
 
event = threading.Event()
 
 
# 紅綠燈
def lighter():
  count = 0
  event.set() # 剛進(jìn)來的時候是綠燈
  while True:
    if 4 < count < 10:
      event.clear() # 清除設(shè)置，阻塞等待
      print("[信號燈]：紅，不能通行", count)
    elif count >= 10: # 添加設(shè)置，繼續(xù)執(zhí)行
      event.set()
      count = 0
    else:
      event.set() # 添加設(shè)置，繼續(xù)執(zhí)行
      print("[信號燈]：綠燈，可以通行", count)
    time.sleep(1)
    count += 1
 
 
# 汽車
def car(name):
  while True:
    if event.is_set():
      print("{0}: 綠燈 , 走起...".format(name))
      time.sleep(1)
    else:
      print("{0}: 紅燈 , 停車...".format(name))
      event.wait()
      print("{0}: 綠燈亮了 , 繼續(xù)前進(jìn)...".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() #創(chuàng)建鎖對象
lock.acquire() #上鎖 如果lock已經(jīng)上鎖再調(diào)用會阻塞
lock.release() #解鎖

from threading import Thread, Lock
from time import sleep
 
a = b = 0
lock = Lock()
 
 
# 子線程輸出a b
def value():
  while True:
    lock.acquire() # 上鎖
    if a != b:
      print("a = %d,b = %d" % (a, b))
    lock.release() # 解鎖
 
 
t = Thread(target=value)
t.start()
 
# 主線程加鎖更改a b時候，子線程處理a b 時也要進(jìn)行加鎖，重復(fù)加鎖就會阻塞等待主線程處理結(jié)束
# 同理主進(jìn)程再次更改a b 時等 子進(jìn)程結(jié)束才可以
while True:
  with lock: # 自動上/解鎖
    a += 1
    b += 1
t.join

from threading import Lock, Thread
 
 
# 交易類
class Account:
  def __init__(self, _id, balance, lock):
    self.id = _id
    self.balance = balance
    self.lock = lock # 各自賬戶鎖
 
  # 取錢
  def withdraw(self, amount):
    self.balance -= amount
 
  # 存錢
  def deposit(self, amount):
    self.balance += amount
 
  # 查看賬戶
  def get_balance(self):
    return self.balance
 
 
# 轉(zhuǎn)賬
def transfer(from_, to, amount):
  if from_.lock.acquire(): # 鎖住自己的賬戶
    from_.withdraw(amount) # 自己賬戶減少
    if to.lock.acquire(): # 鎖住對方賬戶
      to.deposit(amount) # 對方賬戶增加
      to.lock.release() # 解鎖對方賬戶
    from_.lock.release() # 自己賬戶解鎖
  print("轉(zhuǎn)賬完成")
 
 
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())