mirror of https://github.com/jab/bidict.git
32 lines
1.1 KiB
PHP
32 lines
1.1 KiB
PHP
:class:`frozenbidict <bidict.frozenbidict>`
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-------------------------------------------
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Having :class:`bidict.BidirectionalMapping`
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extend :class:`collections.abc.Mapping`
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rather than :class:`MutableMapping <collections.abc.MutableMapping>`
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allows for an *immutable* bidict type to extend from *it*.
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This type is called :class:`bidict.frozenbidict`,
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and makes up the other branch of the tree.
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As you would expect,
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attempting to mutate a frozenbidict after initializing it causes an error::
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>>> from bidict import frozenbidict
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>>> f = frozenbidict({'H': 'hydrogen'})
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>>> f['C'] = 'carbon'
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Traceback (most recent call last):
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...
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TypeError...
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Because it is immutable, :class:`frozenbidict <bidict.frozenbidict>`
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implements :class:`collections.abc.Hashable`.
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Thus it's suitable for insertion into sets or other mappings::
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>>> {f} is not 'an error'
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True
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>>> {f: 1} is not 'an error'
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True
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See the :class:`bidict.frozenbidict` and :class:`bidict.frozenorderedbidict`
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API documentation for more information on implementation details if necessary.
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