A UserList subclass implementing unique list values.

list_01_defaultlist.py

from collections import UserList


class UniquesList(UserList):
    """
    A List Class which works just like a list, except
    that it only holds unique values - similar to a set.

    >>> ul = UniquesList("The Jolly Green Giant")
    >>> print("".join(ul))
    The JolyGrniat
    """
    def __init__(self, initlist=None):
        """__init__.

        Args:
            initlist:
        """

        self.data = []

        if initlist:
            if isinstance(initlist, UniquesList):
                self.data[:] = initlist.data[:]
            else:
                for k in initlist:
                    self.append(k)

    def append(self, item) -> None:
        """Append an item to the end of the list.

        Args:
            item: Only unique values are appended, duplicates are omitted

        Returns:
            None:
        """

        if not self.data.count(item):
            super(UniquesList, self).append(item)


dl = UniquesList()
dl.append("Text Value One")
dl.append("Text Value One")
dl.append("Text Value One")
dl.append("Text Value One")
dl.append("Text Value Two")
dl.append("Text Value Two")
dl.append("Text Value Two")
dl.append("Text Value Two")
assert len(dl) == 2

dl = UniquesList()
dl.append("a" * 1000000000)
assert len(dl) == 1