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From: Stefan Behnel <stefan_ml@behnel.de>
Subject: Re: How can i call array_length to get the length of array object?
Date: Sun, 24 Jun 2012 10:48:20 +0200
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gmspro, 24.06.2012 10:01:
> Why are some methods/functions named in this way in python? __len__
> 
> underscoreunderscoreNAMEunderscoreunderscore
> 
> Is there any speciality of naming such methods?

Yes. Look up "special methods" in the documentation.

You may have noticed the correspondence between len() and __len__(). That
is Python's way of allowing you to implement this kind of generic
functionality (sometimes referred to as a protocol).

You also asked why len() is a function instead of a method. Don't you find
it much easier to use one function for everything than to look up and
sometimes even learn one method for each kind of object you are dealing
with? Python prefers simplicity here. You want the length? Use len().

Stefan