inconsistency with += between different types ?
tdelaney at avaya.com
Wed Aug 7 19:53:17 EDT 2002
> From: Andreas.Leitgeb at siemens.at [mailto:Andreas.Leitgeb at siemens.at]
> That's exactly what I meant.
> For immutable objects, __iadd__ et al. simply make no sense (IMHO).
> To Christopher and other defendants of status quo:
> Do you know of any real use that a not-self-mutating __ixxx__
> may have, which its non-i version __xxx__ could not do ?
Using augmented assignment, a lookup is performed for __iadd__. If that
fails (an AttributeException thrown) then __add__ is looked up. Lookups and
thrown exceptions are expensive.
Immutable objects may well choose to implement __iadd__ for the performance
boost. In that case, the code is usually:
def __add__(self, other):
__radd__ = __iadd__
__iadd__ = __add__
More information about the Python-list