如何在Python中从线程访问全局变量
考虑以下代码:如何在Python中从线程访问全局变量,python,multithreading,thread-safety,Python,Multithreading,Thread Safety,考虑以下代码: from threading import Thread def main(): number = 5 class my_thread(Thread): def __init__(self, range): Thread.__init__(self) self.range = range def run(self): global number
from threading import Thread
def main():
number = 5
class my_thread(Thread):
def __init__(self, range):
Thread.__init__(self)
self.range = range
def run(self):
global number
for i in self.range:
number += 1
t1 = my_thread(range(4))
t1.start()
t1.join()
print number
main()
此程序的输出为
Exception in thread Thread-1:
Traceback (most recent call last):
File "C:\Tools\Python27\lib\threading.py", line 801, in __bootstrap_inner
self.run()
File "C:\Dev\Workspace\Hello World\Hello.py", line 14, in run
number += 1
NameError: global name 'number' is not defined
5
显然,
myu线程
没有访问number
的权限。这是为什么?我如何才能正确访问它 您需要在第一次定义时将number
设为全局,如下所示:
def main():
global number
number = 5
...etc...
您需要在第一次定义时将
number
设为全局,如下所示:
def main():
global number
number = 5
...etc...