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62 lines
1.9 KiB
62 lines
1.9 KiB
# -*- coding: utf-8 -*-
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# Copyright 2009-2019 Joshua Bronson. All Rights Reserved.
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#
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# This Source Code Form is subject to the terms of the Mozilla Public
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# License, v. 2.0. If a copy of the MPL was not distributed with this
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# file, You can obtain one at http://mozilla.org/MPL/2.0/.
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"""Useful functions for working with bidirectional mappings and related data."""
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from itertools import chain, repeat
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from .compat import iteritems, Mapping
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_NULL_IT = repeat(None, 0) # repeat 0 times -> raise StopIteration from the start
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def _iteritems_mapping_or_iterable(arg):
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"""Yield the items in *arg*.
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If *arg* is a :class:`~collections.abc.Mapping`, return an iterator over its items.
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Otherwise return an iterator over *arg* itself.
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"""
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return iteritems(arg) if isinstance(arg, Mapping) else iter(arg)
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def _iteritems_args_kw(*args, **kw):
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"""Yield the items from the positional argument (if given) and then any from *kw*.
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:raises TypeError: if more than one positional argument is given.
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"""
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args_len = len(args)
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if args_len > 1:
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raise TypeError('Expected at most 1 positional argument, got %d' % args_len)
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itemchain = None
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if args:
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arg = args[0]
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if arg:
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itemchain = _iteritems_mapping_or_iterable(arg)
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if kw:
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iterkw = iteritems(kw)
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itemchain = chain(itemchain, iterkw) if itemchain else iterkw
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return itemchain or _NULL_IT
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def inverted(arg):
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"""Yield the inverse items of the provided object.
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If *arg* has a :func:`callable` ``__inverted__`` attribute,
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return the result of calling it.
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Otherwise, return an iterator over the items in `arg`,
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inverting each item on the fly.
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*See also* :attr:`bidict.BidirectionalMapping.__inverted__`
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"""
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inv = getattr(arg, '__inverted__', None)
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if callable(inv):
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return inv()
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return ((val, key) for (key, val) in _iteritems_mapping_or_iterable(arg))
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