variable

(class from pyomo.core.kernel.variable)

class pyomo.core.kernel.variable.variable(domain_type=None, domain=None, lb=None, ub=None, value=None, fixed=False)[source]

Bases: IVariable

A decision variable

Decision variables are used in objectives and constraints to define an optimization problem.

Parameters:

domain_type – Sets the domain type of the variable. Must be one of RealSet or IntegerSet. Can be updated later by assigning to the domain_type property. The default value of None is equivalent to RealSet, unless the domain keyword is used.
domain – Sets the domain of the variable. This updates the domain_type, lb, and ub properties of the variable. The default value of None implies that this keyword is ignored. This keyword can not be used in combination with the domain_type keyword.
lb – Sets the lower bound of the variable. Can be updated later by assigning to the lb property on the variable. Default is None, which is equivalent to -inf.
ub – Sets the upper bound of the variable. Can be updated later by assigning to the ub property on the variable. Default is None, which is equivalent to +inf.
value – Sets the value of the variable. Can be updated later by assigning to the value property on the variable. Default is None.
fixed (bool) – Sets the fixed status of the variable. Can be updated later by assigning to the fixed property or by calling the fix() method. Default is False.

Examples

>>> import pyomo.kernel as pmo
>>> # A continuous variable with infinite bounds
>>> x = pmo.variable()
>>> # A binary variable
>>> x = pmo.variable(domain=pmo.Binary)
>>> # Also a binary variable
>>> x = pmo.variable(domain_type=pmo.IntegerSet, lb=0, ub=1)

__init__(domain_type=None, domain=None, lb=None, ub=None, value=None, fixed=False)[source]

Methods

`__init__`([domain_type, domain, lb, ub, ...])
`activate`()	Activate this object.
`clone`()	Returns a copy of this object with the parent pointer set to `None`.
`deactivate`()	Deactivate this object.
`fix`([value])	Fix the variable.
`free`()	Free the variable.
`getname`([fully_qualified, name_buffer, ...])	Dynamically generates a name for this object.
`has_lb`()	Returns `False` when the lower bound is `None` or negative infinity
`has_ub`()	Returns `False` when the upper bound is `None` or positive infinity
`is_binary`()	Returns `True` when the domain type is `IntegerSet` and the bounds are within [0,1].
`is_component_type`()	Return True if this class is a Pyomo component
`is_constant`()	Returns `False` because this is not a constant in an expression.
`is_continuous`()	Returns `True` when the domain type is `RealSet`.
`is_discrete`()	Returns `True` when the domain type is `IntegerSet`.
`is_expression_type`([expression_system])	Return True if this numeric value is an expression
`is_fixed`()	Returns `True` if this variable is fixed, otherwise returns `False`.
`is_indexed`()	Return True if this numeric value is an indexed object
`is_integer`()	Returns `True` when the domain type is `IntegerSet`.
`is_logical_type`()	Return True if this class is a Pyomo Boolean object.
`is_named_expression_type`()	Return True if this numeric value is a named expression
`is_numeric_type`()	Return True if this class is a Pyomo numeric object
`is_parameter_type`()	Returns `False` because this is not a parameter object.
`is_potentially_variable`()	Returns `True` because this is a variable.
`is_reference`()	Return True if this object is a reference.
`is_relational`()	DEPRECATED.
`is_variable_type`()	Returns `True` because this is a variable object.
`polynomial_degree`()	Return the polynomial degree of this expression
`set_value`(value[, skip_validation])
`to_string`([verbose, labeler, smap, ...])	Return a string representation of the expression tree.
`unfix`()	Free the variable.

Attributes

`active`	The active status of this object.
`bounds`	Get/Set the bounds as a tuple (lb, ub).
`ctype`	The object's category type.
`domain`	Set the domain of the variable.
`domain_type`	The domain type of the variable (`RealSet` or `IntegerSet`)
`fixed`	The fixed status of the variable
`lb`	Return the numeric value of the variable lower bound.
`local_name`	The object's local name within the context of its parent.
`lower`	The lower bound of the variable
`lslack`	Lower slack (value - lb).
`name`	The object's fully qualified name.
`parent`	The object's parent (possibly None).
`slack`	min(lslack, uslack).
`stale`	The stale status of the variable
`storage_key`	The object's storage key within its parent
`ub`	Return the numeric value of the variable upper bound.
`upper`	The upper bound of the variable
`uslack`	Upper slack (ub - value).
`value`	The value of the variable

Member Documentation

activate(): Activate this object.

clone()

Returns a copy of this object with the parent pointer set to None.

A clone is almost equivalent to deepcopy except that any categorized objects encountered that are not descendents of this object will reference the same object on the clone.

deactivate(): Deactivate this object.

fix(value=NOTSET): Fix the variable. Sets the fixed indicator to True. An optional value argument will update the variable’s value before fixing.

free(): Free the variable. Sets the fixed indicator to False.

getname(fully_qualified=False, name_buffer={}, convert=<class 'str'>, relative_to=None)

Dynamically generates a name for this object.

Parameters:

fully_qualified (bool) – Generate a full name by iterating through all ancestor containers. Default is False.
convert (function) – A function that converts a storage key into a string representation. Default is the built-in function str.
relative_to (object) – When generating a fully qualified name, generate the name relative to this block.

Returns:

If a parent exists, this method returns a string representing the name of the object in the context of its parent; otherwise (if no parent exists), this method returns None.

has_lb(): Returns False when the lower bound is None or negative infinity

has_ub(): Returns False when the upper bound is None or positive infinity

is_binary(): Returns True when the domain type is IntegerSet and the bounds are within [0,1].

is_component_type(): Return True if this class is a Pyomo component

is_constant(): Returns False because this is not a constant in an expression.

is_continuous(): Returns True when the domain type is RealSet.

is_discrete(): Returns True when the domain type is IntegerSet.

is_expression_type(expression_system=None): Return True if this numeric value is an expression

is_fixed(): Returns True if this variable is fixed, otherwise returns False.

is_indexed(): Return True if this numeric value is an indexed object

is_integer(): Returns True when the domain type is IntegerSet.

is_logical_type()

Return True if this class is a Pyomo Boolean object.

Boolean objects include constants, variables, or logical expressions.

is_named_expression_type(): Return True if this numeric value is a named expression

is_numeric_type(): Return True if this class is a Pyomo numeric object

is_parameter_type(): Returns False because this is not a parameter object.

is_potentially_variable(): Returns True because this is a variable.

is_reference(): Return True if this object is a reference.

is_relational()

DEPRECATED.

Return True if this numeric value represents a relational expression.

Deprecated since version 6.4.3: is_relational() is deprecated in favor of is_expression_type(ExpressionType.RELATIONAL)

is_variable_type(): Returns True because this is a variable object.

polynomial_degree(): Return the polynomial degree of this expression

to_string(verbose=None, labeler=None, smap=None, compute_values=False)

Return a string representation of the expression tree.

Parameters:

verbose (bool) – If True, then the string representation consists of nested functions. Otherwise, the string representation is an infix algebraic equation. Defaults to False.
labeler – An object that generates string labels for non-constant in the expression tree. Defaults to None.
smap – A SymbolMap instance that stores string labels for non-constant nodes in the expression tree. Defaults to None.
compute_values (bool) – If True, then fixed expressions are evaluated and the string representation of the resulting value is returned.

Returns:

A string representation for the expression tree.

unfix(): Free the variable. Sets the fixed indicator to False.

property active: The active status of this object.

property bounds: Get/Set the bounds as a tuple (lb, ub).

property ctype: The object’s category type.

property domain: Set the domain of the variable. This method updates the domain_type property and overwrites the lb and ub properties with the domain bounds.

property domain_type: The domain type of the variable (RealSet or IntegerSet)

property fixed: The fixed status of the variable

property lb: Return the numeric value of the variable lower bound.

property local_name: The object’s local name within the context of its parent. Alias for obj.getname(fully_qualified=False).

property lower: The lower bound of the variable

property lslack: Lower slack (value - lb). Returns None if the variable value is None.

property name: The object’s fully qualified name. Alias for obj.getname(fully_qualified=True).

property parent: The object’s parent (possibly None).

property slack: min(lslack, uslack). Returns None if the variable value is None.

property stale: The stale status of the variable

property storage_key: The object’s storage key within its parent

property ub: Return the numeric value of the variable upper bound.

property upper: The upper bound of the variable

property uslack: Upper slack (ub - value). Returns None if the variable value is None.

property value: The value of the variable