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35 lines
996 B
Python
35 lines
996 B
Python
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from typing import ChainMap, MutableMapping, TypeVar, cast
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_KT = TypeVar("_KT")
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_VT = TypeVar("_VT")
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class DeepChainMap(ChainMap[_KT, _VT]):
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"""
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Variant of ChainMap that allows direct updates to inner scopes.
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Only works when all passed mapping are mutable.
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"""
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def __setitem__(self, key: _KT, value: _VT) -> None:
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for mapping in self.maps:
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mutable_mapping = cast(MutableMapping[_KT, _VT], mapping)
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if key in mutable_mapping:
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mutable_mapping[key] = value
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return
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cast(MutableMapping[_KT, _VT], self.maps[0])[key] = value
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def __delitem__(self, key: _KT) -> None:
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"""
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Raises
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------
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KeyError
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If `key` doesn't exist.
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"""
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for mapping in self.maps:
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mutable_mapping = cast(MutableMapping[_KT, _VT], mapping)
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if key in mapping:
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del mutable_mapping[key]
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return
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raise KeyError(key)
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