[Tutor] adding methods to native types

[Erik Price]

On Wednesday, February 5, 2003, at 11:43  PM, Sean 'Shaleh' Perry wrote:

> The nice thing about functions is you can pass any object to them. 
> len() works
> on any object that supports __len__().

Strangely, it is more reassuring knowing that len() is just calling 
__len__().  I suppose because at least then the element-counting 
functionality *is* encapsulated within the class, which is where [I 
think] it should be.

So does that mean that if I define a class and add a __len__() method, 
then it will work with the len() function?  Let me try:

 >>> class TestLen:
...  def __len__(self):
...   return 8080
...
 >>> t = TestLen()
 >>> len(t)
8080

Guess so!  But if the len() function simply calls the __len__() method, 
why make that method "magic" at all?  Why not just offer it as a 
regular method?  [To me] there's nothing magic about using a method to 
get some data about an object.


Erik



-- 
Erik Price

email: erikprice@mac.com
jabber: erikprice@jabber.org