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104 lines
3.9 KiB
104 lines
3.9 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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"""Provides :func:`bidict.namedbidict`."""
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import re
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from ._abc import BidirectionalMapping
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from ._bidict import bidict
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from .compat import PY2
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_isidentifier = ( # pylint: disable=invalid-name
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re.compile('[A-Za-z_][A-Za-z0-9_]*$').match if PY2 else str.isidentifier
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)
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def namedbidict(typename, keyname, valname, base_type=bidict):
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r"""Create a new subclass of *base_type* with custom accessors.
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Analagous to :func:`collections.namedtuple`.
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The new class's ``__name__`` and ``__qualname__``
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will be set based on *typename*.
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Instances of it will provide access to their
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:attr:`inverse <BidirectionalMapping.inverse>`\s
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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 subclass of
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:class:`BidirectionalMapping`.
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(This function requires slightly more of *base_type*,
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e.g. the availability of an ``_isinv`` attribute,
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but all the :ref:`concrete bidict types
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<other-bidict-types:Bidict Types Diagram>`
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that the :mod:`bidict` module provides can be passed in.
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Check out the code if you actually need to pass in something else.)
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"""
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# Re the `base_type` docs above:
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# The additional requirements (providing _isinv and __getstate__) do not belong in the
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# BidirectionalMapping interface, and it's overkill to create additional interface(s) for this.
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# On the other hand, it's overkill to require that base_type be a subclass of BidictBase, since
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# that's too specific. The BidirectionalMapping check along with the docs above should suffice.
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if not issubclass(base_type, BidirectionalMapping):
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raise TypeError(base_type)
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names = (typename, keyname, valname)
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if not all(map(_isidentifier, names)) or keyname == valname:
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raise ValueError(names)
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class _Named(base_type): # pylint: disable=too-many-ancestors
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__slots__ = ()
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def _getfwd(self):
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return self.inverse if self._isinv else self
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def _getinv(self):
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return self if self._isinv else self.inverse
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@property
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def _keyname(self):
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return valname if self._isinv else keyname
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@property
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def _valname(self):
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return keyname if self._isinv else valname
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def __reduce__(self):
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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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names = dict(typename=typename, bname=bname, keyname=keyname, valname=valname)
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fdoc = u'{typename} forward {bname}: {keyname} → {valname}'.format(**names)
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idoc = u'{typename} inverse {bname}: {valname} → {keyname}'.format(**names)
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setattr(_Named, fname, property(_Named._getfwd, doc=fdoc)) # pylint: disable=protected-access
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setattr(_Named, iname, property(_Named._getinv, doc=idoc)) # pylint: disable=protected-access
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if not PY2:
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_Named.__qualname__ = _Named.__qualname__[:-len(_Named.__name__)] + typename
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_Named.__name__ = typename
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return _Named
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def _make_empty(typename, keyname, valname, base_type):
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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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