為什么sum=0.0放在開頭會報錯？

sum?=?0.0
def?average(*args):
????if?len(args)?==?0:
????????????return?sum
????for?x?in?args:
????????????sum?=?sum?+?x
????return?sum/len(args)
print?average()
print?average(1,?2)
print?average(1,?2,?2,?3,?4)

Traceback (most recent call last):
? File "index.py", line 8, in
??? print average()
? File "index.py", line 4, in average
??? return sum
UnboundLocalError: local variable 'sum' referenced before assignment

標答的sum=0.0放在def之后，為什么放在開頭就會報錯？

qq_慕雪8441108

2019-07-20

源自：初識Python 7-7

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2 回答

慕婉清2588457
2019-07-20

如果需要全局變量

global?sum?sum?=?0.0
def?average(*args):????
????global?sum
????sum?=?0.0
????if?len(args)?==?0:
????????return?sum
????for?x?in?args:?
????????sum?=?sum?+?x
????????return?sum/len(args)
????print?average()
????print?average(1,?2)
????print?average(1,?2,?2,?3,?4)