python notes 10-thread synchronization of multithreading (lock lock)

foreword

My friends are not unfamiliar with the scene of eating hot pot. When eating hot pot, classmate A puts fish balls in the pot, and classmate B eats fish balls at the same time, which may lead to eating raw fish balls.
In order to avoid this situation, in the process of placing fish balls, first lock the operation, let the friends who eat hot pot stop for a while, and wait for the fish balls to be cooked before eating. So how does python simulate this scenario?

not locked

1. If multiple threads operate on a certain data at the same time, there will be unpredictable results. For example, the following scenario: when friend a is adding fish balls to the hot pot, friend b eats the fish balls at the same time, which is likely to cause the fish balls that have just been placed in the pot to be clipped out (not cooked), or still Before the pot is in, go to the fish balls (can't be caught).

# coding=utf-8
import threading
import time

def chiHuoGuo(people, do):
     print ( " %s friends who eat hot pot: %s " % (time.ctime(),people))
    time.sleep(1)
    for i in range(3):
        time.sleep( 1 )
         print ( " %s %s is making fish balls at %s " % (time.ctime(), people, do))
     print ( " %s friend who eats hot pot: %s " % (time. ctime(),people))


class myThread (threading.Thread): #Inherit    the parent class threading.Thread 
    def  __init__ (self, people, name, do):
         ''' Rewrite the initialization content of threading.Thread ''' 
        threading.Thread .__ init__ (self)
        self.threadName = name
        self.people = people
        self.do = do

    def run(self):    #Write the code to be executed into the run function. After the thread is created, it will run the run function directly. 
        ''' Rewrite the run method ''' 
        print ( " Start thread: " + self.threadName)

        chiHuoGuo(self.people, self.do) #Execute      task print 
        ( " qq communication group: 226296743 " )
         print ( " End thread: " + self.name)

print ( " yoyo invites friends to eat hot pot:!!! " )

#Set thread group 
threads = []

#Create a new thread 
thread1 = myThread( " xiaoming " , " Thread-1 " , " Add " )
thread2 = myThread("xiaowang", "Thread-2", "吃掉")

#Add to thread group 
threads.append(thread1)
threads.append(thread2)

#Open thread 
for thread in threads:
    thread.start()

#Block the main thread and wait for the child thread to end 
for thread in threads:
    thread.join()

time.sleep( 0.1 )
 print ( " Exit the main thread: After eating hot pot, check out and leave " )

 

operation result:

Thread synchronization (lock)

1. In order to avoid the above situation, the concept of lock is introduced. There are two states of lock: locked and unlocked

2. Whenever a thread a wants to access shared data, it must first obtain a lock; if another thread b has already obtained the lock, then let thread a suspend, that is, synchronous blocking; wait until thread b is finished accessing, after releasing the lock , and let thread a continue.

3. Use the two methods in the threading.Lock() class

• acquire() locks
• release() releases the lock

# coding=utf-8
import threading
import time

def chiHuoGuo(people, do):
     print ( " %s friends who eat hot pot: %s " % (time.ctime(),people))
    time.sleep(1)
    for i in range(3):
        time.sleep( 1 )
         print ( " %s %s is making fish balls at %s " % (time.ctime(), people, do))
     print ( " %s friend who eats hot pot: %s " % (time. ctime(),people))


class myThread (threading.Thread): #Inherit    the parent class threading.Thread 

    lock = threading.Lock()   #Thread lock

    def  __init__ (self, people, name, do):
         ''' Rewrite threading.Thread initialization content ''' 
        threading.Thread. __init__ (self)
        self.threadName = name
        self.people = people
        self.do = do

    def run(self):    #Write the code to be executed into the run function. After the thread is created, it will run the run function directly. 
        ''' Rewrite the run method ''' 
        print ( " Start thread: " + self.threadName)

        #Lock the thread before executing the task 
        self.lock.acquire()

        chiHuoGuo(self.people, self.do)      #Execute task

        #After execution, release the lock 
        self.lock.release()

        print ( " qq exchange group: 226296743 " )
         print ( " End thread: " + self.name)

print ( " yoyo invites friends to eat hot pot:!!! " )

#Set thread group 
threads = []

#Create a new thread 
thread1 = myThread( " xiaoming " , " Thread-1 " , " Add " )
thread2 = myThread("xiaowang", "Thread-2", "吃掉")

#Add to thread group 
threads.append(thread1)
threads.append(thread2)

#Open thread 
for thread in threads:
    thread.start()

#Block the main thread and wait for the child thread to end 
for thread in threads:
    thread.join()

time.sleep( 0.1 )
 print ( " Exit the main thread: After eating hot pot, check out and leave " )

 

operation result: