from collections import MutableSet
class SetMixin(MutableSet):
"""
Mix-in for sets. You must define __iter__, add, remove
"""
def __len__(self):
length = 0
for item in self:
length += 1
return length
def __contains__(self, item):
for has_item in self:
if item == has_item:
return True
return False
issubset = MutableSet.__le__
issuperset = MutableSet.__ge__
union = MutableSet.__or__
intersection = MutableSet.__and__
difference = MutableSet.__sub__
symmetric_difference = MutableSet.__xor__
def copy(self):
return set(self)
def update(self, other):
self |= other
def intersection_update(self, other):
self &= other
def difference_update(self, other):
self -= other
def symmetric_difference_update(self, other):
self ^= other
def discard(self, item):
try:
self.remove(item)
except KeyError:
pass
@classmethod
def _from_iterable(cls, it):
return set(it)