nltk.grammar.ProbabilisticProduction

class nltk.grammar.ProbabilisticProduction[source]

Bases: Production, ImmutableProbabilisticMixIn

A probabilistic context free grammar production. A PCFG ProbabilisticProduction is essentially just a Production that has an associated probability, which represents how likely it is that this production will be used. In particular, the probability of a ProbabilisticProduction records the likelihood that its right-hand side is the correct instantiation for any given occurrence of its left-hand side.

See

Production

__init__(lhs, rhs, **prob)[source]

Construct a new ProbabilisticProduction.

Parameters

  • lhs (Nonterminal) – The left-hand side of the new ProbabilisticProduction.

  • rhs (sequence(Nonterminal and terminal)) – The right-hand side of the new ProbabilisticProduction.

  • prob – Probability parameters of the new ProbabilisticProduction.

is_lexical()

Return True if the right-hand contain at least one terminal token.

Return type

bool

is_nonlexical()

Return True if the right-hand side only contains Nonterminals

Return type

bool

lhs()

Return the left-hand side of this Production.

Return type

Nonterminal

logprob()

Return log(p), where p is the probability associated with this object.

Return type

float

prob()

Return the probability associated with this object.

Return type

float

rhs()

Return the right-hand side of this Production.

Return type

sequence(Nonterminal and terminal)

set_logprob(prob)

Set the log probability associated with this object to logprob. I.e., set the probability associated with this object to 2**(logprob).

Parameters

logprob (float) – The new log probability

set_prob(prob)

Set the probability associated with this object to prob.

Parameters

prob (float) – The new probability