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import keyword |
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3
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from ._not_in import not_in |
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5
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DISCARD = object() |
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6
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7
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8
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class Pattern(tuple): |
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"""A matcher that binds a value to a name.""" |
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11
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__slots__ = () |
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def __new__(cls, name: str): |
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if name == "_": |
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return DISCARD |
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if not name.isidentifier(): |
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raise ValueError |
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if keyword.iskeyword(name): |
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raise ValueError |
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return super().__new__(cls, (name,)) |
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@property |
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def name(self): |
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"""Return the name of the matcher.""" |
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return tuple.__getitem__(self, 0) |
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def __getitem__(self, other): |
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return AsPattern(self, other) |
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class AsPattern(tuple): |
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"""A matcher that contains further bindings.""" |
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__slots__ = () |
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def __new__(cls, matcher: Pattern, match): |
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if match is DISCARD: |
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return matcher |
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return super().__new__(cls, (matcher, match)) |
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@property |
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def matcher(self): |
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"""Return the left-hand-side of the as-match.""" |
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return self[0] |
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@property |
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def match(self): |
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"""Return the right-hand-side of the as-match.""" |
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return self[1] |
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51
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52
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class AttrPattern(tuple): |
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"""A matcher that destructures an object using attribute access.""" |
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__slots__ = () |
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def __new__(*args, **kwargs): |
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cls, *args = args |
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if args: |
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raise ValueError(args) |
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return super(AttrPattern, cls).__new__(cls, (tuple(kwargs.items()),)) |
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@property |
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def match_dict(self): |
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return self[0] |
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67
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68
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class DictPattern(tuple): |
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"""A matcher that destructures a dictionary by key.""" |
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__slots__ = () |
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73
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def __new__(cls, match_dict, *, exhaustive=False): |
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return super(DictPattern, cls).__new__( |
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cls, (tuple(match_dict.items()), exhaustive) |
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) |
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@property |
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def match_dict(self): |
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return self[0] |
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82
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@property |
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def exhaustive(self): |
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return self[1] |
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86
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87
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class Bind(tuple): |
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"""A wrapper that adds additional bindings to a successful match.""" |
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90
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__slots__ = () |
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91
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92
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def __new__(*args, **kwargs): |
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cls, structure = args |
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not_in(kwargs, "_") |
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return super(Bind, cls).__new__(cls, (structure, tuple(kwargs.items()))) |
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96
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97
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@property |
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def structure(self): |
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return self[0] |
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100
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101
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@property |
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def bindings(self): |
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return self[1] |
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mwchase /
python-structured-data
