Source code for bidict._util

# -*- coding: utf-8 -*-
# Copyright 2018 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

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

from itertools import chain, repeat

from .compat import iteritems, Mapping

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

[docs]def _iteritems_mapping_or_iterable(arg): """Yield the items in *arg*. If *arg* is a :class:``, return an iterator over its items. Otherwise return an iterator over *arg* itself. """ return iteritems(arg) if isinstance(arg, Mapping) else iter(arg)
[docs]def _iteritems_args_kw(*args, **kw): """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('Expected at most 1 positional argument, got %d' % args_len) itemchain = None if args: arg = args[0] if arg: itemchain = _iteritems_mapping_or_iterable(arg) if kw: iterkw = iteritems(kw) itemchain = chain(itemchain, iterkw) if itemchain else iterkw return itemchain or _NULL_IT
[docs]def inverted(arg): """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() return ((val, key) for (key, val) in _iteritems_mapping_or_iterable(arg))