OrderedSet

orderedset.py

"""Simple OrderedSet implementation."""

from collections import OrderedDict
from collections.abc import MutableSet
from functools import reduce
from itertools import repeat
from operator import or_, sub


class OrderedSet(MutableSet):
    """Set that maintains insertion order."""
    def __init__(self, vals=()):
        self.dict = OrderedDict(zip(vals, repeat(None)))

    def __contains__(self, val):
        return val in self.dict

    def __iter__(self):
        return iter(self.dict)

    def __len__(self):
        return len(self.dict)

    def __repr__(self):
        return "OrderedSet: {" + ", ".join(map(str, self)) + "}"

    def copy(self):
        return OrderedSet(self.dict.copy())

    def add(self, val):
        self.dict[val] = None

    def union(self, *vals):
        return reduce(or_, vals, self)

    def discard(self, val):
        if val in self:
             del self.dict[val]

    def difference(self, *vals):
        return reduce(sub, vals, self)