为什么 python 字符串没有 __iter__ 函数?

问题描述

当字符串没有 __iter__ 函数时，我们如何迭代 python 字符串?

How is it that we can iterate over python strings when strings don't have an __iter__ function?

$ python
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56) 
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> "asdf".__iter__
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'str' object has no attribute '__iter__'
>>> it = iter("asdf")      
>>> it
<iterator object at 0xb736f5ac>
>>> 

更重要的是(无论如何迭代字符串)，为什么 python 字符串不遵循与其他所有内容相同的约定.特别是当 Python 文档说需要 __iter__ 函数时 http://docs.python.org/library/functions.html#iter ?

And more importantly (however strings are iterated over), why do python strings not follow the same convention as everything else. Particularly when the Python docs say that the __iter__ function is needed http://docs.python.org/library/functions.html#iter ?

推荐答案

来自您的链接:

或者它必须支持序列协议(__getitem__() 方法整数参数从 0 开始).

or it must support the sequence protocol (the __getitem__() method with integer arguments starting at 0).

In [1]: 'foo'.__getitem__(0)
Out[1]: 'f'

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