9 多线程对非共享数据

Posted 2020-10-16 不要被骄傲遮蔽了双眼

1.g_num 不是全局变量

from threading import Thread
import time

def test1():
    g_num = 100
    g_num += 1
    print("---1test1--g_num=%d"%g_num)
    time.sleep(2)

def test2():
    time.sleep(1)
    print("---2test2--g_num=%d"%g_num)


t1 = Thread(target=test1)
t1.start()

t2 = Thread(target=test2)
t2.start()

 

### 结果
---1test1--g_num=101
Exception in thread Thread-2:
Traceback (most recent call last):
  File "/usr/lib/python3.5/threading.py", line 914, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.5/threading.py", line 862, in run
    self._target(*self._args, **self._kwargs)
  File "10-多线程-非共享数据.py", line 12, in test2
    print("---2test2--g_num=%d"%g_num)
NameError: name \'g_num\' is not defined

 

 

2.线程名

In [1]: import threading


In [2]: threading.current_thread()
Out[2]: <_MainThread(MainThread, started 139965328148224)>

In [3]: threading.current_thread().name
Out[3]: \'MainThread\'

 

 

3.两个线程执行同一个函数

• 两个线程执行的函数没有关系　　
• 函数个人是个人的，函数里面的变量没有关系

 

from threading import Thread
import threading
import time

def test1():
    name = threading.current_thread().name
    print("---the thread is %s--"%name)
    g_num = 100
    if name == "Thread-1":
        g_num += 1
        print("---%s--g_num=%d"%(name,g_num))
    else:
        time.sleep(2)
        print("----%s--g_num=%d"%(name,g_num))


t1 = Thread(target=test1)
t1.start()

t2 = Thread(target=test1)
t2.start()

　　　　

 　　　　　　

 

 

小总结

• 在多线程开发中，全局变量是多个线程都共享的数据，而局部变量等是各自线程的，是非共享的