nltk.parse.chart.TreeEdge

class documentation

class TreeEdge(EdgeI): (source)

Known subclasses: nltk.parse.featurechart.FeatureTreeEdge, nltk.parse.pchart.ProbabilisticTreeEdge

Constructor: TreeEdge(span, lhs, rhs, dot)

An edge that records the fact that a tree is (partially) consistent with the sentence. A tree edge consists of:

A span, indicating what part of the sentence is consistent with the hypothesized tree.
A left-hand side, specifying the hypothesized tree's node value.
A right-hand side, specifying the hypothesized tree's children. Each element of the right-hand side is either a terminal, specifying a token with that terminal as its leaf value; or a nonterminal, specifying a subtree with that nonterminal's symbol as its node value.
A dot position, indicating which children are consistent with part of the sentence. In particular, if dot is the dot position, rhs is the right-hand size, (start,end) is the span, and sentence is the list of tokens in the sentence, then tokens[start:end] can be spanned by the children specified by rhs[:dot].

For more information about edges, see the EdgeI interface.

Static Method	`from_production`	Return a new `TreeEdge` formed from the given production. The new edge's left-hand side and right-hand side will be taken from `production`; its span will be `(index,index)`; and its dot position will be `0`.
Method	`__init__`	Construct a new `TreeEdge`.
Method	`__repr__`	Undocumented
Method	`__str__`	Undocumented
Method	`dot`	Return this edge's dot position, which indicates how much of the hypothesized structure is consistent with the sentence. In particular, `self.rhs[:dot]` is consistent with `tokens[self.start():self.end()]`...
Method	`end`	Return the end index of this edge's span.
Method	`is_complete`	Return True if this edge's structure is fully consistent with the text.
Method	`is_incomplete`	Return True if this edge's structure is partially consistent with the text.
Method	`length`	Return the length of this edge's span.
Method	`lhs`	Return this edge's left-hand side, which specifies what kind of structure is hypothesized by this edge.
Method	`move_dot_forward`	Return a new `TreeEdge` formed from this edge. The new edge's dot position is increased by `1`, and its end index will be replaced by `new_end`.
Method	`nextsym`	Return the element of this edge's right-hand side that immediately follows its dot.
Method	`rhs`	Return this edge's right-hand side, which specifies the content of the structure hypothesized by this edge.
Method	`span`	Return a tuple `(s, e)`, where `tokens[s:e]` is the portion of the sentence that is consistent with this edge's structure.
Method	`start`	Return the start index of this edge's span.
Instance Variable	`_comparison_key`	Undocumented
Instance Variable	`_dot`	Undocumented
Instance Variable	`_lhs`	Undocumented
Instance Variable	`_rhs`	Undocumented
Instance Variable	`_span`	Undocumented

Inherited from EdgeI:

Method	`__eq__`	Undocumented
Method	`__hash__`	Undocumented
Method	`__lt__`	Undocumented
Method	`__ne__`	Undocumented
Instance Variable	`_hash`	Undocumented

@staticmethod
def from_production(production, index): (source) ¶

overridden in nltk.parse.featurechart.FeatureTreeEdge, nltk.parse.pchart.ProbabilisticTreeEdge

Return a new TreeEdge formed from the given production. The new edge's left-hand side and right-hand side will be taken from production; its span will be (index,index); and its dot position will be 0.

Returns
TreeEdge	Undocumented

def __init__(self, span, lhs, rhs, dot=0): (source) ¶

overrides nltk.parse.chart.EdgeI.__init__

overridden in nltk.parse.featurechart.FeatureTreeEdge, nltk.parse.pchart.ProbabilisticTreeEdge

Construct a new TreeEdge.

Parameters
span:tuple(int, int)	A tuple `(s, e)`, where `tokens[s:e]` is the portion of the sentence that is consistent with the new edge's structure.
lhs:Nonterminal	The new edge's left-hand side, specifying the hypothesized tree's node value.
rhs:list(Nonterminal and str)	The new edge's right-hand side, specifying the hypothesized tree's children.
dot:int	The position of the new edge's dot. This position specifies what prefix of the production's right hand side is consistent with the text. In particular, if `sentence` is the list of tokens in the sentence, then `okens[span[0]:span[1]]` can be spanned by the children specified by `rhs[:dot]`.

def __repr__(self): (source) ¶

Undocumented

def __str__(self): (source) ¶

overridden in nltk.parse.featurechart.FeatureTreeEdge

Undocumented

def dot(self): (source) ¶

overrides nltk.parse.chart.EdgeI.dot

Return this edge's dot position, which indicates how much of the hypothesized structure is consistent with the sentence. In particular, self.rhs[:dot] is consistent with tokens[self.start():self.end()].

Returns
int	Undocumented

def end(self): (source) ¶

overrides nltk.parse.chart.EdgeI.end

Return the end index of this edge's span.

Returns
int	Undocumented

def is_complete(self): (source) ¶

overrides nltk.parse.chart.EdgeI.is_complete

Return True if this edge's structure is fully consistent with the text.

Returns
bool	Undocumented

def is_incomplete(self): (source) ¶

overrides nltk.parse.chart.EdgeI.is_incomplete

Return True if this edge's structure is partially consistent with the text.

Returns
bool	Undocumented

def length(self): (source) ¶

overrides nltk.parse.chart.EdgeI.length

Return the length of this edge's span.

Returns
int	Undocumented

def lhs(self): (source) ¶

overrides nltk.parse.chart.EdgeI.lhs

Return this edge's left-hand side, which specifies what kind of structure is hypothesized by this edge.

See Also
`TreeEdge` and `LeafEdge` for a description of the left-hand side values for each edge type.

def move_dot_forward(self, new_end): (source) ¶

overridden in nltk.parse.featurechart.FeatureTreeEdge

Return a new TreeEdge formed from this edge. The new edge's dot position is increased by 1, and its end index will be replaced by new_end.

Parameters
new_end:int	The new end index.
Returns
TreeEdge	Undocumented

def nextsym(self): (source) ¶

overrides nltk.parse.chart.EdgeI.nextsym

Return the element of this edge's right-hand side that immediately follows its dot.

Returns
Nonterminal or terminal or None	Undocumented

def rhs(self): (source) ¶

overrides nltk.parse.chart.EdgeI.rhs

Return this edge's right-hand side, which specifies the content of the structure hypothesized by this edge.

See Also
`TreeEdge` and `LeafEdge` for a description of the right-hand side values for each edge type.

def span(self): (source) ¶

overrides nltk.parse.chart.EdgeI.span

Return a tuple (s, e), where tokens[s:e] is the portion of the sentence that is consistent with this edge's structure.

Returns
tuple(int, int)	Undocumented

def start(self): (source) ¶

overrides nltk.parse.chart.EdgeI.start

Return the start index of this edge's span.

Returns
int	Undocumented

_comparison_key = (source) ¶

overridden in nltk.parse.featurechart.FeatureTreeEdge, nltk.parse.pchart.ProbabilisticTreeEdge

Undocumented

_dot = (source) ¶

Undocumented

_lhs = (source) ¶

Undocumented

_rhs = (source) ¶

Undocumented

_span = (source) ¶

Undocumented