Package nltk_lite :: Module featurestructure :: Class FeatureBindings

Class FeatureBindings

object --+
         |
        FeatureBindings

A partial mapping from feature variables to values. Simple variables can be either bound (i.e., assigned a value), or unbound (i.e., left unspecified). Aliased variables can additionally be inconsistant (i.e., assigned multiple incompatible values).

Instance Methods

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__init__(self, initial_bindings=None)
Construct a new set of bindings.

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list of FeatureVariable

bound_variables(self)
Returns: A list of all simple variables that have been assigned values.

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bool

is_bound(self, variable)
Returns: True if the given variable is bound.

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lookup(self, variable, update_aliased_bindings=True)
Returns: The value that it assigned to the given variable, if it's bound; or the variable itself if it's unbound.

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bind(self, variable, value)
Assign a value to a variable.

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copy(self)
Returns: a copy of this set of bindings.

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__repr__(self)
Returns: a string representation of this set of bindings.

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__cmp__(self, other)

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

Instance Variables

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_bindings
A dictionary mapping from bound variables to their values.

Properties

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Inherited from object: __class__

Method Details

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init(self, initial_bindings=None)
(Constructor)

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Construct a new set of bindings.

Parameters:

initial_bindings - A dictionary from variables to values, specifying the initial assignments for the bound variables.

Overrides: object.__init__

bound_variables(self)

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Returns: list of FeatureVariable: A list of all simple variables that have been assigned values.

is_bound(self, variable)

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Returns: bool: True if the given variable is bound. A simple variable is bound if it has been assigned a value. An aliased variable is bound if at least one of its aliases is bound and all of its bound aliases are assigned the same value.

lookup(self, variable, update_aliased_bindings=True)

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Parameters:

update_aliased_bindings - If true, then looking up a bound aliased variable will cause any unbound aliases it has to be bound to its value. E.g., if ?x is bound to 1 and ?y is unbound, then looking up ?x=y will cause ?y to be bound to 1.

Returns:

The value that it assigned to the given variable, if it's bound; or the variable itself if it's unbound. The value assigned to an aliased variable is defined as the value that's assigned to its bound aliases.

Raises:

ValueError - If variable is an aliased variable with an inconsistant value (i.e., if two or more of its bound aliases are assigned different values).

bind(self, variable, value)

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Assign a value to a variable. If variable is an aliased variable, then the value is assigned to all of its aliases. Variables can only be bound to values; they may not be bound to other variables.

Raises:

ValueError - If value is a variable.

copy(self)

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Returns:: a copy of this set of bindings.

repr(self)
(Representation operator)

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repr(x)

Returns:: a string representation of this set of bindings.
Overrides: object.__repr__

Class FeatureBindings

__init__(self, initial_bindings=None) (Constructor)

bound_variables(self)

is_bound(self, variable)

lookup(self, variable, update_aliased_bindings=True)

bind(self, variable, value)

copy(self)

__repr__(self) (Representation operator)

init(self, initial_bindings=None)
(Constructor)

repr(self)
(Representation operator)