Learn Python together: multithreading-sharing global variables

Multithreading-sharing global variables

From threadingImport ThreadImport Timeg_num =100def work1 (): global g_num for i in range (3): G_num + = 1 print ( "----in Work1, G_num is%d---"%g_num) def work2 (): global g_num print ( "----in Work2, G_num is%d---"%g_num) print ( "---thread was created before G_num is%d---"%g_num) T1 = thread (TARGET=WORK1) T1.start ()  #延时一会, make sure things in the T1 thread are done time.sleep (1) t2 = thread (TARGET=WORK2) T2.start ()    

Operation Result:

is 100-------in work1, g_num is 103-------in work2, g_num is 103---

The list is passed to the thread as an argument

from threading import threadimport timedef work1 (nums): Nums.append (44) print ( "----in Work1---", nums) def work2 (nums): # Delay a while to ensure that things in the T1 thread are done time.sleep (1) print ( "----in WORK2---", nums) G_nums = [11,22,33]t1 = Thread ( Target=work1, args= (G_nums,)) T1.start () t2 = Thread (Target=work2, args= (g_nums)) T2.start ()     

Operation Result:

----in work1--- [11, 22, 33, 44]----in work2--- [11, 22, 33, 44]

Summarize:

Sharing global variables across all threads within a process makes it easy to share data among multiple threads
The downside is that a thread is arbitrarily modifying a global variable that can cause confusion among multiple threads about global variables (that is, thread non-security)

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Learn Python together: multithreading-sharing global variables