In article <mailman.2010.1312731312.1164.python-l...@python.org>, John O'Hagan <resea...@johnohagan.com> wrote:
> I'm looking for good ways to ensure that attributes are only writable such > that they retain the characteristics the class requires. Sounds like you're trying to do http://en.wikipedia.org/wiki/Design_by_contract. Which is not a bad thing. But, I think a more pythonic way to implement this would be to verify behaviors, not types. I would start by writing a assert_invarient() method which validates the object. I'm guessing all you really need is that you can index [0] and [1] and get ints, so test for that. Something like: def assert_invarient(self): try: assert isinstance(data[0], int) assert isinstance(data[1], int) except: raise ValueError Then, call this from inside your __init__(), __setitem__(), etc. -- http://mail.python.org/mailman/listinfo/python-list
