CODEWITHSUNDEEP
pyomo
adowling
adowling

Reputation: 47

How to get all variables in a constraint in Pyomo?

My question is simple. Given a Pyomo constraint, how can I easily extract the variables that appear in the constraint?

This question has been asked a few times already. I believe the Pyomo internals have been modified and the proposed solutions no longer work.

How to get variables of a constraint in Pyomo

Access all variables occurring in a pyomo constraint

Minimum working test problem:

from pyomo.environ import *

m = ConcreteModel()

m.I = Set(initialize=[i for i in range(5)])

m.x = Var(m.I,bounds=(-10,10),initialize=1.0)
m.z = Var(bounds=(-100,100), initialize=5.0)

m.con1 = Constraint(expr=m.x[0] + m.x[1] - m.x[3] >= 10)
m.con2 = Constraint(expr=m.x[0]*m.x[3] + m.x[1] >= 0)
m.con3 = Constraint(expr=m.x[4]*m.x[3] + m.x[0]*m.x[3] - m.x[4] == 0)

m.obj = Objective(expr=sum(m.x[i]**2 for i in m.I))

m.pprint()

opt = SolverFactory('ipopt')
opt.options['max_iter'] = 0
opt.solve(m, tee=True)

In this example, I would like to programmatically inspect the variables in con1.

Upvotes: 0

Views: 175

Answers (1)

Qi Chen
Qi Chen

Reputation: 1718

The second link has the correct solution: Access all variables occurring in a pyomo constraint

identify_variables() still exists, but it looks like it was moved to pyomo.core.expr.visitor. It might be worth promoting it into the pyomo.core.expr namespace.

Upvotes: 1

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