Class OrderedSet

django/utils/datastructures.py:5–42

A set which keeps the ordering of the inserted items.

class OrderedSet:
    """
    A set which keeps the ordering of the inserted items.
    """

    def __init__(self, iterable=None):
        self.dict = dict.fromkeys(iterable or ())

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

    def remove(self, item):
        del self.dict[item]

    def discard(self, item):
        try:
            self.remove(item)
        except KeyError:
            pass

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

    def __reversed__(self):
        return reversed(self.dict)

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

    def __bool__(self):
        return bool(self.dict)

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

    def __repr__(self):
        data = repr(list(self.dict)) if self.dict else ""
        return f"{self.__class__.__qualname__}({data})"


class MultiValueDictKeyError(KeyError):