ThreadLocal

import threading
    
# 创建全局ThreadLocal对象:
local_school = threading.local()

def process_student():
    # 获取当前线程关联的student:
    std = local_school.student
    print('Hello, %s (in %s)' % (std, threading.current_thread().name))

def process_thread(name):
    # 绑定ThreadLocal的student:
    local_school.student = name
    process_student()

t1 = threading.Thread(target= process_thread, args=('Alice',), name='Thread-A')
t2 = threading.Thread(target= process_thread, args=('Bob',), name='Thread-B')
t1.start()
t2.start()
t1.join()
t2.join()

执行结果：

Hello, Alice (in Thread-A)
Hello, Bob (in Thread-B)

全局变量 local_school 就是一个 ThreadLocal 对象，每个 Thread 对它都可以读写 student 属性，但互不影响。你可以把 local_school 看成全局变量，但每个属性如 local_school.student 都是线程的局部变量，可以任意读写而互不干扰，也不用管理锁的问题，ThreadLocal 内部会处理。

可以理解为全局变量 local_school 是一个 dict，不但可以用 local_school.student，还可以绑定其他变量，如 local_school.teacher 等等。

ThreadLocal 最常用的地方就是为每个线程绑定一个数据库连接，HTTP 请求，用户身份信息等，这样一个线程的所有调用到的处理函数都可以非常方便地访问这些资源。

Reference

ThreadLocal - https://www.liaoxuefeng.com/wiki/1016959663602400/1017630786314240

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【Python】线程 - ThreadLocal

ThreadLocal

Reference

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