On Sun, 18 Jan 2009 15:11:46 -0500, Terry Reedy wrote: > andrew cooke wrote: >> Context - >> http://docs.python.org/3.0/reference/datamodel.html?highlight=data >> model#object.__iadd__ >> >> Just a suggestion I thought I'd throw out... There's a restriction in >> the language implementation on exactly what can go the left of an >> augmented arithmetic expression. >> >> For example: >>>>> a = 3 >>>>> a **= 2 >> >> is ok, but: >>>>> class Foo(): >> ... def __init__(): >> ... self.a = 3 >> ... def __ipow__(self, x): >> ... self.a **= x >> ... >>>>> Foo() **= 2 > > Calls return objects and therefore cannot be the target of an > assignment, augmented or otherwise. The target of an assignment is a > name or collection slot, both of which are grammatical constructs, not > objects.
There's a practical reason too. You create a new Foo instance, mutate it with the augmented assignment operator, and then a tenth of a millisecond later the garbage collector throws it away because it has a reference count of zero. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
