Source code for bidict._util

# -*- 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/.


"""Useful functions for working with bidirectional mappings and related data."""

from collections.abc import Mapping
from itertools import chain, repeat

from ._typing import KT, VT, IterItems, MapOrIterItems


_NULL_IT = repeat(None, 0)  # repeat 0 times -> raise StopIteration from the start


[docs]def _iteritems_mapping_or_iterable(arg: MapOrIterItems[KT, VT]) -> IterItems[KT, VT]: """Yield the items in *arg*. If *arg* is a :class:`~collections.abc.Mapping`, return an iterator over its items. Otherwise return an iterator over *arg* itself. """ return iter(arg.items() if isinstance(arg, Mapping) else arg)
[docs]def _iteritems_args_kw(*args: MapOrIterItems[KT, VT], **kw: VT) -> IterItems[KT, VT]: """Yield the items from the positional argument (if given) and then any from *kw*. :raises TypeError: if more than one positional argument is given. """ args_len = len(args) if args_len > 1: raise TypeError(f'Expected at most 1 positional argument, got {args_len}') itemchain = None if args: arg = args[0] if arg: itemchain = _iteritems_mapping_or_iterable(arg) if kw: iterkw = iter(kw.items()) itemchain = chain(itemchain, iterkw) if itemchain else iterkw # type: ignore return itemchain or _NULL_IT # type: ignore
def inverted(arg: MapOrIterItems[KT, VT]) -> IterItems[VT, KT]: """Yield the inverse items of the provided object. If *arg* has a :func:`callable` ``__inverted__`` attribute, return the result of calling it. Otherwise, return an iterator over the items in `arg`, inverting each item on the fly. *See also* :attr:`bidict.BidirectionalMapping.__inverted__` """ inv = getattr(arg, '__inverted__', None) if callable(inv): return inv() # type: ignore return ((val, key) for (key, val) in _iteritems_mapping_or_iterable(arg))