[Tutor] class question

[alan.gauld@bt.com]

> >>>class adder:
>        def __init__(self, value=0):
>           self.data=value               #initialize data
>        def __add__(self, other):
>            self.data=self.data + other   #add other in-place

So adding updates the internal value, see below...

>        def __repr__(self):
>            return `self.data`          #convert to string
> ...
> ...
> >>>x=adder(1)     #__init__
> >>>x=2; x=2       #__add__

Assuming x=2 should be x+2....
This adds 2 to x twice, so after the first time x=3, 
then second time round x = 5

> >>>x               #__repr__
> 5

Which is what we see here.

Alan g.
Author of the 'Learning to Program' web site
http://www.freenetpages.co.uk/hp/alan.gauld