Source code for bidict._dup

# -*- coding: utf-8 -*-
# Copyright 2009-2020 Joshua Bronson. All Rights Reserved.
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.


"""Provide :class:`OnDup` and related functionality."""


from collections import namedtuple
from enum import Enum


class OnDupAction(Enum):
    """An action to take to prevent duplication from occurring."""

    #: Raise a :class:`~bidict.DuplicationError`.
    RAISE = 'RAISE'
    #: Overwrite existing items with new items.
    DROP_OLD = 'DROP_OLD'
    #: Keep existing items and drop new items.
    DROP_NEW = 'DROP_NEW'

    def __repr__(self) -> str:
        return f'<{self.name}>'


RAISE = OnDupAction.RAISE
DROP_OLD = OnDupAction.DROP_OLD
DROP_NEW = OnDupAction.DROP_NEW


class OnDup(namedtuple('_OnDup', 'key val kv')):
    r"""A 3-tuple of :class:`OnDupAction`\s specifying how to handle the 3 kinds of duplication.

    *See also* :ref:`basic-usage:Values Must Be Unique`

    If *kv* is not specified, *val* will be used for *kv*.
    """

    __slots__ = ()

    def __new__(cls, key: OnDupAction = DROP_OLD, val: OnDupAction = RAISE, kv: OnDupAction = RAISE) -> 'OnDup':
        """Override to provide user-friendly default values."""
        return super().__new__(cls, key, val, kv or val)


#: Default :class:`OnDup` used for the
#: :meth:`~bidict.bidict.__init__`,
#: :meth:`~bidict.bidict.__setitem__`, and
#: :meth:`~bidict.bidict.update` methods.
ON_DUP_DEFAULT = OnDup()
#: An :class:`OnDup` whose members are all :obj:`RAISE`.
ON_DUP_RAISE = OnDup(key=RAISE, val=RAISE, kv=RAISE)
#: An :class:`OnDup` whose members are all :obj:`DROP_OLD`.
ON_DUP_DROP_OLD = OnDup(key=DROP_OLD, val=DROP_OLD, kv=DROP_OLD)