Thomas Heller wrote:
> I'm trying to implement __iter__ on an abstract base class while I don't
> know whether subclasses support that or not.
> Hope that makes sense, if not, this code should be clearer:
>
> class Base:
> def __getattr__(self, name):
> if name == "__iter__" and hasattr(self, "Iterator"):
> return self.Iterator
> raise AttributeError, name
> Is there any way I could make the above code work with new style
> classes?
Obligatory metaclass approach:
class Base:
class __metaclass__(type):
def __new__(mcl, name, bases, classdict):
try:
classdict["__iter__"] = classdict["Iterator"]
except KeyError:
pass
return type.__new__(mcl, name, bases, classdict)
class Alpha(Base):
def Iterator(self): yield 42
class Beta(Base):
def __getitem__(self, index):
return [1, 2, 3, "ganz viele"][index]
for item in Alpha(): print item
for item in Beta(): print item,
print
Peter
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