nltk.chunk.regexp.RegexpChunkRule

class documentation

class RegexpChunkRule(object): (source)

Known subclasses: nltk.chunk.regexp.ChunkRule, nltk.chunk.regexp.ChunkRuleWithContext, nltk.chunk.regexp.ExpandLeftRule, nltk.chunk.regexp.ExpandRightRule, nltk.chunk.regexp.MergeRule, nltk.chunk.regexp.SplitRule, nltk.chunk.regexp.StripRule, nltk.chunk.regexp.UnChunkRule

Constructor: RegexpChunkRule(regexp, repl, descr)

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A rule specifying how to modify the chunking in a ChunkString, using a transformational regular expression. The RegexpChunkRule class itself can be used to implement any transformational rule based on regular expressions. There are also a number of subclasses, which can be used to implement simpler types of rules, based on matching regular expressions.

Each RegexpChunkRule has a regular expression and a replacement expression. When a RegexpChunkRule is "applied" to a ChunkString, it searches the ChunkString for any substring that matches the regular expression, and replaces it using the replacement expression. This search/replace operation has the same semantics as re.sub.

Each RegexpChunkRule also has a description string, which gives a short (typically less than 75 characters) description of the purpose of the rule.

This transformation defined by this RegexpChunkRule should only add and remove braces; it should not modify the sequence of angle-bracket delimited tags. Furthermore, this transformation may not result in nested or mismatched bracketing.

Static Method	`fromstring`	Create a RegexpChunkRule from a string description. Currently, the following formats are supported:
Method	`__init__`	Construct a new RegexpChunkRule.
Method	`__repr__`	Return a string representation of this rule. It has the form:
Method	`apply`	Apply this rule to the given `ChunkString`. See the class reference documentation for a description of what it means to apply a rule.
Method	`descr`	Return a short description of the purpose and/or effect of this rule.
Instance Variable	`_descr`	Undocumented
Instance Variable	`_regexp`	Undocumented
Instance Variable	`_repl`	Undocumented

@staticmethod
def fromstring(s): (source) ¶

Create a RegexpChunkRule from a string description. Currently, the following formats are supported:

{regexp}         # chunk rule
}regexp{         # strip rule
regexp}{regexp   # split rule
regexp{}regexp   # merge rule

Where regexp is a regular expression for the rule. Any text following the comment marker (#) will be used as the rule's description:

>>> from nltk.chunk.regexp import RegexpChunkRule
>>> RegexpChunkRule.fromstring('{<DT>?<NN.*>+}')
<ChunkRule: '<DT>?<NN.*>+'>

def __init__(self, regexp, repl, descr): (source) ¶

overridden in nltk.chunk.regexp.ChunkRule, nltk.chunk.regexp.ChunkRuleWithContext, nltk.chunk.regexp.ExpandLeftRule, nltk.chunk.regexp.ExpandRightRule, nltk.chunk.regexp.MergeRule, nltk.chunk.regexp.SplitRule, nltk.chunk.regexp.StripRule, nltk.chunk.regexp.UnChunkRule

Construct a new RegexpChunkRule.

Parameters
regexp:regexp or str	The regular expression for this `RegexpChunkRule`. When this rule is applied to a `ChunkString`, any substring that matches `regexp` will be replaced using the replacement string `repl`. Note that this must be a normal regular expression, not a tag pattern.
repl:str	The replacement expression for this `RegexpChunkRule`. When this rule is applied to a `ChunkString`, any substring that matches `regexp` will be replaced using `repl`.
descr:str	A short description of the purpose and/or effect of this rule.

def __repr__(self): (source) ¶

Return a string representation of this rule. It has the form:

<RegexpChunkRule: '{<IN|VB.*>}'->'<IN>'>

Note that this representation does not include the description string; that string can be accessed separately with the descr() method.

Returns
str	Undocumented

def apply(self, chunkstr): (source) ¶

Apply this rule to the given ChunkString. See the class reference documentation for a description of what it means to apply a rule.

Parameters
chunkstr:ChunkString	The chunkstring to which this rule is applied.
Returns
None	Undocumented
Raises
`ValueError`	If this transformation generated an invalid chunkstring.

def descr(self): (source) ¶

Return a short description of the purpose and/or effect of this rule.

Returns
str	Undocumented

_descr = (source) ¶

Undocumented

_regexp = (source) ¶

Undocumented

_repl = (source) ¶

Undocumented