Difference: __iadd__ and __add__

[Jonathan Gardner]

I would like to point out that it isn't entirely obvious where to find
documentation for this particular thing. I know from experience where
to go, but I remember spending a long time trying to hunt this down.

For reference, you may want to check out the index of the language
reference manual.

http://www.python.org/doc/2.4.2/ref/genindex.html