Variable¶
Variable objects are used to represents each variable of the optimization problem. When the optimization is performed, the combination of variable values that optimizes the objective function, while not violating any constraints will be identified.
The type of a variable (‘continuous’, ‘integer’ or ‘binary’) can be set using the type
keyword of the constructor or it can be changed after initialization by var.type = 'binary'
.
The variable class subclasses the sympy.Symbol
class, which means that symbolic expressions of variables can be constructed by using regular python syntax, e.g. my_expression = 2 * var1 + 3 * var2 ** 2
. Expressions like this are used when constructing Constraint and Objective objects.
Once a problem has been optimized, the primal and dual values of a variable can be accessed from the primal
and dual
attributes, respectively.

class
optlang.interface.
Variable
(name, lb=None, ub=None, type='continuous', problem=None, *args, **kwargs)[source]¶ Bases:
sympy.core.symbol.Symbol
Optimization variables.
Variable objects are used to represents each variable of the optimization problem. When the optimization is performed, the combination of variable values that optimizes the objective function, while not violating any constraints will be identified. The type of a variable (‘continuous’, ‘integer’ or ‘binary’) can be set using the type keyword of the constructor or it can be changed after initialization by
var.type = 'binary'
.The variable class subclasses the
sympy.Symbol
class, which means that symbolic expressions of variables can be constructed by using regular python syntax, e.g.my_expression = 2 * var1 + 3 * var2 ** 2
. Expressions like this are used when constructing Constraint and Objective objects. Once a problem has been optimized, the primal and dual values of a variable can be accessed from the primal and dual attributes, respectively.Examples
>>> Variable('x', lb=10, ub=10) '10 <= x <= 10'
Attributes
name: str The variable’s name. lb: float or None, optional The lower bound, if None then inf. ub: float or None, optional The upper bound, if None then inf. type: str, optional The variable type, ‘continuous’ or ‘integer’ or ‘binary’. problem: Model or None, optional A reference to the optimization model the variable belongs to. Methods

classmethod
clone
(variable, **kwargs)[source]¶ Make a copy of another variable. The variable being copied can be of the same type or belong to a different solver interface.

default_assumptions
= {}¶

dual
¶ The dual of variable (None if no solution exists).

lb
¶ Lower bound of variable.

name
¶ Name of variable.

primal
¶ The primal of variable (None if no solution exists).

to_json
()[source]¶ Returns a jsoncompatible object from the Variable that can be saved using the json module.

type
¶ Variable type (‘either continuous, integer, or binary’.)

ub
¶ Upper bound of variable.

classmethod