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from ._adt_constructor import ADTConstructor |
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from ._match_failure import MatchFailure |
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from ._not_in import not_in |
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from ._patterns import AsPattern |
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from ._patterns import AttrPattern |
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from ._patterns import Bind |
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from ._patterns import DictPattern |
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from ._patterns import Pattern |
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from ._unpack import unpack |
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class Destructurer: |
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def __init__(self, target): |
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self.target = target |
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def __call__(self, value): |
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return self.destructure(value) |
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def destructure(self, value): |
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raise NotImplementedError |
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type = None |
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class AsPatternDestructurer(Destructurer): |
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def destructure(self, value): |
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if isinstance(value, AsPattern): |
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if value is self.target: |
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return reversed(value) |
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return (value.match, value) |
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return (value, value) |
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type = AsPattern |
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class ADTDestructurer(Destructurer): |
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def destructure(self, value): |
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if value.__class__ is not self.target.__class__: |
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raise MatchFailure |
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return reversed(unpack(value)) |
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type = ADTConstructor |
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def guarded_getattr(value, target_key): |
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try: |
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return getattr(value, target_key) |
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except AttributeError: |
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raise MatchFailure |
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def value_cant_be_smaller(target_match_dict, value_match_dict): |
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if len(value_match_dict) < len(target_match_dict): |
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raise MatchFailure |
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def key_destructure(value, match_dict, getter): |
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return [getter(value, target_key) for (target_key, _) in reversed(match_dict)] |
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def same_type_destructure(target_match_dict, value_match_dict): |
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for (target_key, _), (value_key, value_value) in zip( |
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target_match_dict, value_match_dict |
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): |
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if target_key != value_key: |
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raise MatchFailure |
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yield value_value |
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class AttrPatternDestructurer(Destructurer): |
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def destructure(self, value): |
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if isinstance(value, AttrPattern): |
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value_cant_be_smaller(self.target.match_dict, value.match_dict) |
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return reversed( |
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list(same_type_destructure(self.target.match_dict, value.match_dict)) |
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) |
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return key_destructure(value, self.target.match_dict, guarded_getattr) |
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type = AttrPattern |
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def guarded_getitem(value, target_key): |
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try: |
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return value[target_key] |
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except KeyError: |
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raise MatchFailure |
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def exhaustive_length_must_match(target, value_match_dict): |
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if target.exhaustive and len(value_match_dict) != len(target.match_dict): |
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raise MatchFailure |
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class DictPatternDestructurer(Destructurer): |
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def destructure(self, value): |
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if isinstance(value, DictPattern): |
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value_cant_be_smaller(self.target.match_dict, value.match_dict) |
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exhaustive_length_must_match(self.target, value.match_dict) |
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return reversed( |
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list(same_type_destructure(self.target.match_dict, value.match_dict)) |
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) |
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exhaustive_length_must_match(self.target, value) |
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return key_destructure(value, self.target.match_dict, guarded_getitem) |
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type = DictPattern |
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class TupleDestructurer(Destructurer): |
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def destructure(self, value): |
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if isinstance(value, self.target.__class__) and len(self.target) == len(value): |
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return reversed(value) |
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raise MatchFailure |
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type = tuple |
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117
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class DestructurerList(tuple): |
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__slots__ = () |
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121
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def __new__(cls, *destructurers): |
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return super().__new__(cls, destructurers) |
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def get_destructurer(self, item): |
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for destructurer in self: |
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if isinstance(item, destructurer.type): |
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return destructurer(item) |
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return None |
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129
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@classmethod |
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def custom(cls, *destructurers): |
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return cls( |
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*destructurers, |
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AsPatternDestructurer, |
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ADTDestructurer, |
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AttrPatternDestructurer, |
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DictPatternDestructurer, |
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TupleDestructurer |
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) |
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141
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def names(self, target): |
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name_list = [] |
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names_seen = set() |
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extra_names = () |
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if isinstance(target, Bind): |
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extra_names = target.bindings |
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target = target.structure |
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to_process = [target] |
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while to_process: |
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item = to_process.pop() |
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if isinstance(item, Pattern): |
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not_in(names_seen, item.name) |
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names_seen.add(item.name) |
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name_list.append(item.name) |
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else: |
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destructurer = self.get_destructurer(item) |
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if destructurer: |
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to_process.extend(destructurer(item)) |
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for (name, _) in extra_names: |
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not_in(names_seen, name) |
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names_seen.add(name) |
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name_list.append(name) |
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return name_list |
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164
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165
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166
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DESTRUCTURERS = DestructurerList.custom() |
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167
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mwchase /
python-structured-data
