Class WeightedGrammar
source code
object --+
|
cfg.Grammar --+
|
WeightedGrammar
A probabilistic context-free grammar. A Weighted Grammar consists of
a start state and a set of weighted productions. The set of terminals
and nonterminals is implicitly specified by the productions.
PCFG productions should be WeightedProductions.
WeightedGrammars impose the constraint that the set of
productions with any given left-hand-side must have probabilities that
sum to 1.
If you need efficient key-based access to productions, you can use a
subclass to implement it.
|
|
__init__(self,
start,
productions)
Create a new context-free grammar, from the given start state and set
of WeightedProductions. |
source code
|
|
|
Inherited from cfg.Grammar:
__repr__,
__str__,
productions,
start
Inherited from object:
__delattr__,
__getattribute__,
__hash__,
__new__,
__reduce__,
__reduce_ex__,
__setattr__
|
float
|
EPSILON = 0.01
The acceptable margin of error for checking that productions with a
given left-hand side have probabilities that sum to 1.
|
__init__(self,
start,
productions)
(Constructor)
| source code
|
Create a new context-free grammar, from the given start state and set
of WeightedProductions.
- Parameters:
start (Nonterminal) - The start symbolproductions (list of Production) - The list of productions that defines the grammar - Raises:
ValueError - if the set of productions with any left-hand-side do not have
probabilities that sum to a value within EPSILON of 1. - Overrides:
cfg.Grammar.__init__
|