__coerce__ vs. new-style classes
Hallvard B Furuseth
h.b.furuseth at usit.uio.no
Mon Aug 2 23:11:31 CEST 2004
> Without __coerce__, what should __add__(self, other) do if it doesn't
> know how to add the arguments, but the other argument might know how?
> It can't just call other.__radd__(self): That might give up and call
> __add__ again.
Uh... please pretend I didn't say that.
You are right, I haven't gotten coerce() straight yet.
> In some cases it might help to call coerce() by hand, but I note the
> ref manual says 'In Python 3.0, coercion will not be supported.'.
Even so, coerce() by hand seems pretty cumbersome. The code I could
come up with for the general case is as follows. Am I missing something
def __add__(self, other):
if not isinstance(other, Myclass):
newself, other = coerce(self, other)
if newself != self:
# Or maybe the above should test if
# newself.__class__ != self.__class__, and do
# self = newself if they have the same class.
...real __add__(Myclass, Myclass) starts here...
More information about the Python-list