Global variables ThreadLocal thread

Global variables within the thread -ThreadLocal

• For each thread gets variable values, use only function by value, but for multi-level functions, parameter passing is too much trouble

• ThreadLocal Solutions

    import threading  
  
    
    local_school = threading.local()  
  
    def process_student():  
        # 获取当前线程关联的studnet  
        std = local_school.student  
        # 对当前线程的全局变量拥有修改权  
        local_school.student = 'my'+local_school.student  
        print("hello, %s (in %s)" % (std, threading.current_thread().name))  
  
    def process_stu():  
        # 对当前线程的全局变量拥有修改权  
        std = local_school.student  
        print("hello, %s (in %s)" % (std, threading.current_thread().name))  
  
    def process_thread(name):  
        # 绑定ThreadLocal的studnet  
        local_school.student = name  
        process_student()  
        process_stu()  
        print(local_school.student)  
  
    t1 = threading.Thread(target大专栏  线程全局变量ThreadLocaltor">=process_thread, args=('Alce',), name="Thread-A")  
    t2 = threading.Thread(target=process_thread, args=('Bob',), name="Thread-B")  
    t1.start()  
    t2.start()  
    t1.join()  
    t2.join()  

  Export

    hello, Alce (in Thread-A)  
    hello, myAlce (in Thread-A)  
    myAlce  
    hello, Bob (in Thread-B)  
    hello, myBob (in Thread-B)  
    myBob  

• Analytical
  global variable is a local_school ThreadLocal objects, you can write and read each Thread student attributes, but independently of each other. You can local_school as global variables, but each attribute as local_school.student local variables are thread, which could be read without any interference, it does not lock management issues, ThreadLocal internal handles.

  It can be understood as a global variable local_school is a dict, not only with local_school.student, can also bind to other variables, such as local_school.teacher and so on.

  ThreadLocal most common place is binding for each thread a database connection, HTTP request, the user identity information, so that all calls to the handler thread can easily access these resources