Why don't python strings have an __iter__ method?
Question:
How is it that we can iterate over python strings when strings don’t provide an __iter__ method?
$ 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>
>>>
My understanding from the documentation is that an __iter__ method is required for iteration. Why don’t Python strings follow the same convention, and how do they provide iteration without doing so?
Answers:
From your link:
or it must support the sequence
protocol (the __getitem__() method
with integer arguments starting at 0).
In [1]: 'foo'.__getitem__(0)
Out[1]: 'f'
Probably because Python isn’t a langage that has a “char” type. The natural thing to return, if string did have __iter__ would be chars, but there are no chars. I can see a case for hooking __iter__ up to string and doing whatever list(someString) does, not really sure why it’s not that way.
How is it that we can iterate over python strings when strings don’t provide an __iter__ method?
$ 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>
>>>
My understanding from the documentation is that an __iter__ method is required for iteration. Why don’t Python strings follow the same convention, and how do they provide iteration without doing so?
From your link:
or it must support the sequence
protocol (the__getitem__()method
with integer arguments starting at 0).
In [1]: 'foo'.__getitem__(0)
Out[1]: 'f'
Probably because Python isn’t a langage that has a “char” type. The natural thing to return, if string did have __iter__ would be chars, but there are no chars. I can see a case for hooking __iter__ up to string and doing whatever list(someString) does, not really sure why it’s not that way.