On Sat, 06 Feb 2010 23:53:53 +0100, Martin Drautzburg wrote: > Hello all > > When I create an Object and set its __iter__ method from outside > > s = Sequence #one of my own classes > s.__iter__ = new.instancemethod(f,s,Sequence)
I'm confused as to why you are aliasing your class before changing it. The above just makes s an alternative name for Sequence. Did you mean this? s = Sequence() # make an instance of the class > I get different results, depending on whether I call > > > for x in y.__iter__(): > print x What's y? Where does it come from? Is y supposed to be an instance of Sequence? > or > > for x in y: > print x > > The first case does what I expected, i.e. it iterates over whatever f() > yields. In the second case nothing is printed. I have the impression > that it still calls the original __iter__() method (the one defined at > the class level). Yes, that's almost certainly what is happening. As an optimization, Python bypasses the instance for special methods __NAME__. > Why is that so? > How can I replace the __iter__() method so it does what I want. The best solution is, find another way to do what you want. The clunky solution is to use delegation to wrap your class, and have the outer class re-direct calls to special methods to the instance first. > The reason I want to do such things is I need to implement operations > similar to what itertools do. However I want my own classes and the > operations are only similar to itertools, but differ in significant > details. I don't understand this. If you want iterator operations "similar to itertools", why does this mean you need to replace anything? Just create your own iterators. Or use pre-processing and post-processing to get what you want. Can you show an example of what you would like to happen? -- Steven -- http://mail.python.org/mailman/listinfo/python-list
