名字好难取唷
问题描述
为什么在类上定义 __getitem__ 会使其可迭代?
Why does defining __getitem__ on a class make it iterable?
例如，如果我写:
class b:
def __getitem__(self, k):
return k
cb = b()
for k in cb:
print k
我得到了输出:
0 1 2 3 4 5 6 7 8 ...
我真的希望看到for k in cb:"返回错误
I would really expect to see an error returned from "for k in cb:"
推荐答案
如果你看看 PEP234 定义迭代器，它说:
If you take a look at PEP234 defining iterators, it says:
1. An object can be iterated over with "for" if it implements __iter__() or __getitem__(). 2. An object can function as an iterator if it implements next().
