preferred syntax for list extend?

[Bernhard Herzog]

Greg Ewing <greg at cosc.canterbury.ac.nz> writes:

> Bernhard Herzog wrote:
> > 
> > Why would you want to implement __iadd__ for immutable objects?
> 
> So that, e.g. i += 1 works when i is an integer.

You don't need __iadd__ for that and indeed the int implementation in
2.1.3 does not have the __iadd__ method (more precisely, its C-level
equivalent). The interpreter automatically falls back to using __add__
so that i += 1 becomes equivalent to i = i + 1. The only difference is
that in e.g. x[i] += 1, i is only be evaluated once, as I understand it
anyway.

An immutable object implementing __iadd__ to behave different than
__add__ is probably asking for trouble, although in some rare
circumstances it might offer some optimizations not possible with
__add__ but I can't think of one at the moment.


   Bernhard

-- 
Intevation GmbH                                 http://intevation.de/
Sketch                                 http://sketch.sourceforge.net/
MapIt!                                           http://www.mapit.de/