???????

?????????????????????????????????????????????????????????????κι????????????????????????? ??? ????????????? ?????? ?????б???????????????????????飬???????????????????????

??t??????

??7.3 ??t??????

#!/usr/bin/python
# Filename: func_local.py

def func(x):
    print 'x is', x
    x = 2
    print 'Changed local x to', x

x = 50
func(x)
print 'x is still', x

????????code/func_local.py??

???

$ python func_local.py
x is 50
Changed local x to 2
x is still 50

????ι???

??????У????????????x?? ? ?????Python??ú??????????βε????

??????????????2????x??x???????????????????????????????????x???????????????ж????x???????

????????print????У???????????????е?x??????????????

???global???

??????????????????????????????????????????Python?????????????????????? ??? ??????????global?????????????????global????????????????????????????????

?????????????????????????????????????????????????????????????????????????????????????t??????????????????????ó?????????????????????????????????global???????????????????????????鶨????

??7.4 ???global???

#!/usr/bin/python
# Filename: func_global.py

def func():
    global x

    print 'x is', x
    x = 2
    print 'Changed local x to', x

x = 50
func()
print 'Value of x is', x

????????code/func_global.py??

???

$ python func_global.py
x is 50
Changed global x to 2
Value of x is 2

????ι???

global???????????x????????????????????????????????x?????????仯?????????????????????x????????

????????????global?????????????????????global x, y, z??