It's good that you're using Python 2.3, which does have sets available,
as a previous poster mentioned. Users of Python 2.2 or earlier can get
most of the Set functionality using the following class (from Peter
Norvig's utils.py file):
# class Set:
# """This implements the Set class from PEP 218, except it does not
# overload the infix operators.
# Ex: s = Set([1,2,3]); 1 in s ==> True; 4 in s ==> False
# s.add(4); 4 in s ==> True; len(s) ==> 4
# s.discard(999); s.remove(4); 4 in s ==> False
# s2 = Set([3,4,5]); s.union(s2) ==> Set([1,2,3,4,5])
# s.intersection(s2) ==> Set([3])
# Set([1,2,3]) ==> Set([3,2,1]); repr(s) ==> '{1, 2, 3}'
# for e in s: pass"""
#
# def __init__(self, elements=[]):
# self.dict = {}
# for e in elements:
# self.dict[e] = 1
#
# def __contains__(self, element):
# return element in self.dict
#
# def __getitem__(self, i):
# return self.dict.items()
#
# def add(self, element):
# self.dict[element] = 1
#
# def remove(self, element):
# del self.dict[element]
#
# def discard(self, element):
# if element in self.dict:
# del self.dict[element]
#
# def pop(self):
# key, val = self.dict.popitem()
# return key
#
# def clear(self):
# self.dict.clear()
#
# def union(self, other):
# return Set(self).union_update(other)
#
# def intersection(self, other):
# return Set(self).intersection_update(other)
#
# def union_update(self, other):
# for e in other:
# self.add(e)
# return self
#
# def intersection_update(self, other):
# for e in self.dict.keys():
# if e not in other:
# self.remove(e)
# return self
#
# def issubset(self, other):
# for e in self.dict.keys():
# if e not in other:
# return False
# return True
#
# def __iter__(self):
# for e in self.dict:
# yield e
#
# def __len__(self):
# return len(self.dict)
#
# def __cmp__(self, other):
# if self is other: return False
# if not isinstance(other, Set): return id(self) - id(other)
# return cmp(self.dict, other.dict)
#
# def __repr__(self):
# return "{%s}" % ", ".join([str(e) for e in self.dict.keys()])
Michael
