grid.SetVar

class grid.SetVar(id, initial_value)[source]

Bases: Expr

Set-valued decision variable, with elements from the node-id universe.

Returned by RoutingModel.add_nodes_set_var() and VehicleType.add_nodes_set_var(). Provides set-algebra methods (add(), remove(), contains(), is_empty(), len()) that build Expr instances usable in constraints and transitions.

Instances are typically obtained via RoutingModel.add_nodes_set_var() and VehicleType.add_nodes_set_var(), not constructed directly.

Parameters:

id (int) – Unique identifier of the variable.
initial_value (set or list) – Initial contents of the set.

id

Variable identifier.

Type:: int

type

Always "setvar".

Type:: str

initial_value

Initial contents.

Type:: set or list

preference

Set variables do not carry a solver preference.

Type:: None

Examples

>>> import grid
>>> model = grid.RoutingModel()
>>> vehicle = model.add_vehicle_type(id=0, count=1, capacity=10)
>>> stations = vehicle.add_nodes_set_var(initial_value={3, 4})
>>> stations
SetVar_0
>>> stations.contains(3)
Expr(contains, SetVar_0, SetElem_3, boolean)
>>> stations.remove(3)
Expr(remove, SetVar_0, SetElem_3, set)

__init__(id, initial_value)[source]

Parameters:: id (int)

Methods

`__init__`(id, initial_value)
`add`(element)	Return an expression representing the set with `element` added.
`contains`(element)	Return a boolean expression testing membership of `element`.
`is_empty`()	Return a boolean expression testing whether the set is empty.
`len`()	Return an integer expression giving the cardinality of the set.
`remove`(element)	Return an expression representing the set with `element` removed.
`same`(other)	Return whether this set variable refers to the same id as `other`.

add(element)[source]

Return an expression representing the set with element added.

Parameters:: element (int or Expr) – Element to add.
Returns:: Expression of type "set".
Return type:: Expr

Examples

>>> import grid
>>> model = grid.RoutingModel()
>>> vehicle = model.add_vehicle_type(id=0, count=1, capacity=10)
>>> stations = vehicle.add_nodes_set_var(initial_value={3, 4})
>>> stations.add(5)
Expr(add, SetVar_0, SetElem_5, set)

contains(element)[source]

Return a boolean expression testing membership of element.

Parameters:: element (int or Expr) – Element to test.
Returns:: Boolean expression.
Return type:: Expr

Examples

>>> import grid
>>> model = grid.RoutingModel()
>>> vehicle = model.add_vehicle_type(id=0, count=1, capacity=10)
>>> stations = vehicle.add_nodes_set_var(initial_value={3, 4})
>>> stations.contains(3)
Expr(contains, SetVar_0, SetElem_3, boolean)

is_empty()[source]

Return a boolean expression testing whether the set is empty.

Returns:: Boolean expression.
Return type:: Expr

Examples

>>> import grid
>>> model = grid.RoutingModel()
>>> vehicle = model.add_vehicle_type(id=0, count=1, capacity=10)
>>> stations = vehicle.add_nodes_set_var(initial_value={3, 4})
>>> stations.is_empty()
Expr(empty, SetVar_0, None, boolean)

len()[source]

Return an integer expression giving the cardinality of the set.

Returns:: Integer expression.
Return type:: Expr

Examples

>>> import grid
>>> model = grid.RoutingModel()
>>> vehicle = model.add_vehicle_type(id=0, count=1, capacity=10)
>>> stations = vehicle.add_nodes_set_var(initial_value={3, 4})
>>> stations.len()
Expr(add, SetVar_0, None, integer)

remove(element)[source]

Return an expression representing the set with element removed.

Parameters:: element (int or Expr) – Element to remove.
Returns:: Expression of type "set".
Return type:: Expr

Examples

>>> import grid
>>> model = grid.RoutingModel()
>>> vehicle = model.add_vehicle_type(id=0, count=1, capacity=10)
>>> stations = vehicle.add_nodes_set_var(initial_value={3, 4})
>>> stations.remove(4)
Expr(remove, SetVar_0, SetElem_4, set)

same(other)[source]

Return whether this set variable refers to the same id as other.

Parameters:: other (SetVar)
Return type:: bool

Examples

>>> import grid
>>> model = grid.RoutingModel()
>>> vehicle = model.add_vehicle_type(id=0, count=1, capacity=10)
>>> s1 = vehicle.add_nodes_set_var(initial_value={1})
>>> s2 = vehicle.add_nodes_set_var(initial_value={2})
>>> s1.same(s1)
True
>>> s1.same(s2)
False