Package nltk :: Module cfg :: Class Production

Class Production

object --+
         |
        Production

Known Subclasses:

WeightedProduction

A context-free grammar production. Each production expands a single Nonterminal (the left-hand side) to a sequence of terminals and Nonterminals (the right-hand side). terminals can be any immutable hashable object that is not a Nonterminal. Typically, terminals are strings representing word types, such as "dog" or "under".

Abstractly, a Grammar production indicates that the right-hand side is a possible instantiation of the left-hand side. Grammar productions are context-free, in the sense that this instantiation should not depend on the context of the left-hand side or of the right-hand side.

See Also:: Grammar, Nonterminal

Instance Methods

[hide private]

__init__(self, lhs, rhs)
Construct a new Production. source code

Nonterminal

lhs(self)
Returns: the left-hand side of this Production. source code

sequence of (Nonterminal and (terminal))

rhs(self)
Returns: the right-hand side of this Production. source code

string

__str__(self)
Returns: A verbose string representation of the Production. source code

string

__repr__(self)
Returns: A concise string representation of the Production. source code

boolean

__eq__(self, other)
Returns: true if this Production is equal to other. source code

__ne__(self, other)

source code

__cmp__(self, other)

source code

int

__hash__(self)
Returns: A hash value for the Production. source code

Inherited from object: __delattr__, __getattribute__, __new__, __reduce__, __reduce_ex__, __setattr__

Instance Variables

[hide private]

Nonterminal _lhs
The left-hand side of the production.

tuple of (Nonterminal and (terminal)) _rhs
The right-hand side of the production.

Properties

[hide private]

Inherited from object: __class__

Method Details

[hide private]

init(self, lhs, rhs)
(Constructor)

source code

Construct a new Production.

Parameters:

lhs (Nonterminal) - The left-hand side of the new Production.
rhs (sequence of (Nonterminal and (terminal))) - The right-hand side of the new Production.

Overrides: object.__init__