Notes on concurrent programming of vegetables (V) thread safety and lock solution

Series index ： Concurrent programming notes of vegetables | Python Concurrent programming details （ Continuous updating ~）

List of articles

• • One 、 Introduction to thread safety concepts
  • Two 、Lock Used to solve thread safety problems
  • 3、 ... and 、 Code details

One 、 Introduction to thread safety concepts

Two 、Lock Used to solve thread safety problems

The first way is to manually obtain , Manually release... After execution , It cannot be locked without releasing other programs . The second is easier to use ,with It will release resources after program execution .

3、 ... and 、 Code details

We use threading Module built in Lock Method to create a lock object , Take withdrawing money as an example , The following code can only be executed after obtaining the lock .

stay main In the function, we initialize a Account object , Create two threads ta and tb, Let both threads start executing , The first thread executes normally , The second thread can only obtain the lock after the first thread is executed . If this code is unlocked , If two threads execute at the same time, the balance will be negative .

import threading
import time

lock = threading.Lock()

class Account:
    def __init__(self, balance):
        self.balance = balance

def draw(account, amount):
    with lock:
        if account.balance >= amount:
            time.sleep(0.1)
            print(threading.current_thread().name," Take money successfully ")
            account.balance -= amount
            print(threading.current_thread().name," balance ", account.balance)
        else:
            print(threading.current_thread().name," Failed to withdraw money , Lack of balance ")

if __name__ == "__main__":
    account = Account(1000)
    ta = threading.Thread(name="ta", target=draw, args=(account, 800))
    tb = threading.Thread(name="tb", target=draw, args=(account, 800))

    ta.start()
    tb.start()

utilize Lock To solve thread safety problems is very common , In the next article, let's use Thread pool To solve this kind of problem , Semaphore mechanism It also plays a big role in thread safety , Welcome to your attention , I will keep updating ~

Python Advanced concurrent programming is continuously updated , welcome Like collection ＋ Focus on

Last one ： Concurrent programming notes of vegetables |（ Four ）Python Actual producer - Consumer mode multithreaded crawler
Next ： Concurrent programming notes of vegetables |（ 6、 ... and ） How to use thread pool to transform crawler program

My level is limited , Please comment and correct the deficiencies in the article in the comment area below ~

If feelings help you , Point a praise Give me a hand ~

Share... From time to time Interesting 、 Have a material 、 Nutritious content , welcome Subscribe to follow My blog , Looking forward to meeting you here ~