100 lines
3.7 KiB
Python
100 lines
3.7 KiB
Python
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# -*- coding: utf-8 -*-
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# Copyright 2009-2020 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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"""Provide :func:`bidict.namedbidict`."""
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import typing as _t
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from sys import _getframe
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from ._abc import BidirectionalMapping, KT, VT
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from ._bidict import bidict
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def namedbidict(
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typename: str,
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keyname: str,
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valname: str,
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*,
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base_type: _t.Type[BidirectionalMapping[KT, VT]] = bidict,
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) -> _t.Type[BidirectionalMapping[KT, VT]]:
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r"""Create a new subclass of *base_type* with custom accessors.
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Like :func:`collections.namedtuple` for bidicts.
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The new class's ``__name__`` and ``__qualname__`` will be set to *typename*,
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and its ``__module__`` will be set to the caller's module.
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Instances of the new class will provide access to their
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:attr:`inverse <BidirectionalMapping.inverse>` instances
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via the custom *keyname*\_for property,
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and access to themselves
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via the custom *valname*\_for property.
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*See also* the :ref:`namedbidict usage documentation
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<other-bidict-types:\:func\:\`~bidict.namedbidict\`>`
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:raises ValueError: if any of the *typename*, *keyname*, or *valname*
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strings is not a valid Python identifier, or if *keyname == valname*.
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:raises TypeError: if *base_type* is not a :class:`BidirectionalMapping` subclass
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that provides ``_isinv`` and :meth:`~object.__getstate__` attributes.
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(Any :class:`~bidict.BidictBase` subclass can be passed in, including all the
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concrete bidict types pictured in the :ref:`other-bidict-types:Bidict Types Diagram`.
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"""
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if not issubclass(base_type, BidirectionalMapping) or not all(hasattr(base_type, i) for i in ('_isinv', '__getstate__')):
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raise TypeError(base_type)
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names = (typename, keyname, valname)
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if not all(map(str.isidentifier, names)) or keyname == valname:
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raise ValueError(names)
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class _Named(base_type): # type: ignore
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__slots__ = ()
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def _getfwd(self) -> '_Named':
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return self.inverse if self._isinv else self # type: ignore
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def _getinv(self) -> '_Named':
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return self if self._isinv else self.inverse # type: ignore
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@property
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def _keyname(self) -> str:
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return valname if self._isinv else keyname
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@property
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def _valname(self) -> str:
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return keyname if self._isinv else valname
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def __reduce__(self) -> '_t.Tuple[_t.Callable[[str, str, str, _t.Type[BidirectionalMapping]], BidirectionalMapping], _t.Tuple[str, str, str, _t.Type[BidirectionalMapping]], dict]':
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return (_make_empty, (typename, keyname, valname, base_type), self.__getstate__())
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bname = base_type.__name__
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fname = valname + '_for'
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iname = keyname + '_for'
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fdoc = f'{typename} forward {bname}: {keyname} → {valname}'
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idoc = f'{typename} inverse {bname}: {valname} → {keyname}'
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setattr(_Named, fname, property(_Named._getfwd, doc=fdoc))
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setattr(_Named, iname, property(_Named._getinv, doc=idoc))
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_Named.__name__ = typename
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_Named.__qualname__ = typename
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_Named.__module__ = _getframe(1).f_globals.get('__name__') # type: ignore
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return _Named
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def _make_empty(
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typename: str,
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keyname: str,
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valname: str,
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base_type: _t.Type[BidirectionalMapping] = bidict,
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) -> BidirectionalMapping:
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"""Create a named bidict with the indicated arguments and return an empty instance.
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Used to make :func:`bidict.namedbidict` instances picklable.
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"""
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cls = namedbidict(typename, keyname, valname, base_type=base_type)
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return cls()
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