from threading import Thread import time g_num = 100 def 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("---線程創建之前g_num is %d---"%g_num) t1 = Thread(target=work1) t1.start() #延時一會，保證t1線程中的事情做完 time.sleep(1) t2 = Thread(target=work2) t2.start() 運行結果:
---線程創建之前g_num is 100--- ----in work1, g_num is 103--- ----in work2, g_num is 103--- 列表當做實參傳遞到線程中
from threading import Thread import time def work1(nums): nums.append(44) print("----in work1---",nums) def work2(nums): #延時一會，保證t1線程中的事情做完 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() 運行結果:
----in work1--- [11, 22, 33, 44] ----in work2--- [11, 22, 33, 44] 總結：
- 在一個進程內的所有線程共享全局變量，很方便在多個線程間共享數據
- 缺點就是，線程是對全局變量隨意遂改可能造成多線程之間對全局變量的混亂（即線程非安全）