I have a variable b_i. b is a binary variable which indicates whether to buy a product i or not. i has a value ranging from 1 to 3.

In mathematical format, the binary variable I want to declare looks like follows:

b_i ∈ {0, 1} i = 1, 2, 3

I know variable can be declared using following code in Pyomo

from pyomo.environ import *
b = Var(domain = Binary)

But I am not sure how I can show that b is binary only for given values of i. How can I represent the above binary variable for given values using Pyomo in Python?

CodePudding user response：

You simply need to declare the index set and then the index set (or multiple sets, if multi-indexed) reference is the first argument to the variable creation. There are several examples in the dox and this section on Sets.

import pyomo.environ as pyo

m = pyo.ConcreteModel('example')

m.I = pyo.Set(initialize=[1, 2, 3])
m.b = pyo.Var(m.I, domain=pyo.Binary)

# some nonsense objective...
m.obj = pyo.Objective(expr=sum(m.b[i] for i in m.I))

m.pprint()

CodePudding user response：

Alternative way to do it seems to be as follows:

from pyomo.environ import *

model = ConcreteModel()
    
model.i = RangeSet(1,3)
model.b = Var(model.i, domain = Binary)