[EMAIL PROTECTED] wrote: > Hello, > > I came accross what i think is a serious bug in the python interpreter. > > Membership testing seems not to work for list of objects when these > objects have a user-defined __cmp__ method. > It is present in Python 2.3 and 2.4. I don't know about other versions. > The following code illustrates the bug: > from random import choice > class OBJ: > def __init__(self,identifier): > self.id=identifier > self.allocated=0 > def __cmp__(self,other): > return cmp(other.allocated,self.allocated) > mylist=[OBJ(i) for i in range(20)] > excluded=[obj for obj in mylist if obj.id>choice(range(20))] > for obj in mylist: > if obj in excluded: > assert obj.id in [objt.id for objt in excluded] > continue > I presume you just put the "continue" in there for fun?
>>> for obj in mylist: ... print obj in excluded ... True True True True True True True True True True True True True True True True True True True True >>> OBJ(0) == OBJ(1) True > Running the above snippet will trigger the assert. The culprit seems to > be the __cmp__ method which sorts on a key with constant value. Well indeed. As far as I can see your objects will all test equal. Did you mean the __cmp__ method to return cmp(other.id, self.id)? regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC www.holdenweb.com PyCon TX 2006 www.python.org/pycon/ -- http://mail.python.org/mailman/listinfo/python-list
