125 lines
4.0 KiB
Python
125 lines
4.0 KiB
Python
# Natural Language Toolkit: Text Trees
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#
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# Copyright (C) 2001-2023 NLTK Project
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# Author: Edward Loper <edloper@gmail.com>
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# Steven Bird <stevenbird1@gmail.com>
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# Peter Ljunglöf <peter.ljunglof@gu.se>
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# Tom Aarsen <>
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# URL: <https://www.nltk.org/>
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# For license information, see LICENSE.TXT
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from nltk.probability import ProbabilisticMixIn
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from nltk.tree.parented import MultiParentedTree, ParentedTree
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from nltk.tree.tree import Tree
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class ImmutableTree(Tree):
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def __init__(self, node, children=None):
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super().__init__(node, children)
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# Precompute our hash value. This ensures that we're really
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# immutable. It also means we only have to calculate it once.
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try:
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self._hash = hash((self._label, tuple(self)))
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except (TypeError, ValueError) as e:
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raise ValueError(
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"%s: node value and children " "must be immutable" % type(self).__name__
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) from e
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def __setitem__(self, index, value):
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raise ValueError("%s may not be modified" % type(self).__name__)
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def __setslice__(self, i, j, value):
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raise ValueError("%s may not be modified" % type(self).__name__)
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def __delitem__(self, index):
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raise ValueError("%s may not be modified" % type(self).__name__)
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def __delslice__(self, i, j):
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raise ValueError("%s may not be modified" % type(self).__name__)
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def __iadd__(self, other):
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raise ValueError("%s may not be modified" % type(self).__name__)
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def __imul__(self, other):
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raise ValueError("%s may not be modified" % type(self).__name__)
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def append(self, v):
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raise ValueError("%s may not be modified" % type(self).__name__)
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def extend(self, v):
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raise ValueError("%s may not be modified" % type(self).__name__)
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def pop(self, v=None):
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raise ValueError("%s may not be modified" % type(self).__name__)
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def remove(self, v):
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raise ValueError("%s may not be modified" % type(self).__name__)
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def reverse(self):
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raise ValueError("%s may not be modified" % type(self).__name__)
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def sort(self):
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raise ValueError("%s may not be modified" % type(self).__name__)
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def __hash__(self):
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return self._hash
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def set_label(self, value):
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"""
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Set the node label. This will only succeed the first time the
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node label is set, which should occur in ImmutableTree.__init__().
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"""
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if hasattr(self, "_label"):
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raise ValueError("%s may not be modified" % type(self).__name__)
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self._label = value
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class ImmutableProbabilisticTree(ImmutableTree, ProbabilisticMixIn):
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def __init__(self, node, children=None, **prob_kwargs):
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ImmutableTree.__init__(self, node, children)
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ProbabilisticMixIn.__init__(self, **prob_kwargs)
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self._hash = hash((self._label, tuple(self), self.prob()))
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# We have to patch up these methods to make them work right:
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def _frozen_class(self):
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return ImmutableProbabilisticTree
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def __repr__(self):
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return f"{Tree.__repr__(self)} [{self.prob()}]"
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def __str__(self):
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return f"{self.pformat(margin=60)} [{self.prob()}]"
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def copy(self, deep=False):
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if not deep:
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return type(self)(self._label, self, prob=self.prob())
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else:
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return type(self).convert(self)
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@classmethod
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def convert(cls, val):
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if isinstance(val, Tree):
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children = [cls.convert(child) for child in val]
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if isinstance(val, ProbabilisticMixIn):
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return cls(val._label, children, prob=val.prob())
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else:
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return cls(val._label, children, prob=1.0)
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else:
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return val
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class ImmutableParentedTree(ImmutableTree, ParentedTree):
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pass
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class ImmutableMultiParentedTree(ImmutableTree, MultiParentedTree):
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pass
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__all__ = [
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"ImmutableProbabilisticTree",
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"ImmutableTree",
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"ImmutableParentedTree",
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"ImmutableMultiParentedTree",
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]
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