Why does Python code use len() function instead of

Question

I know that python has a len() function that is used to determine the size of a string, but I was wondering why it's not a method of the string object.

Update

Ok, I realized I was embarrassingly mistaken. __len__() is actually a method of a string object. It just seems weird to see object oriented code in Python using the len function on string objects. Furthermore, it's also weird to see __len__ as the name instead of just len.

Answer 1

Strings do have a length method: __len__()

The protocol in Python is to implement this method on objects which have a length and use the built-in len() function, which calls it for you, similar to the way you would implement __iter__() and use the built-in iter() function (or have the method called behind the scenes for you) on objects which are iterable.

See Emulating container types for more information.

Here's a good read on the subject of protocols in Python: Python and the Principle of Least Astonishment

Answer 2

There is a len method:

>>> a = 'a string of some length'
>>> a.__len__()
23
>>> a.__len__
<method-wrapper '__len__' of str object at 0x02005650>