I am working on a Pyomo model with indexed variables, expressions, and constraints, and I am getting some warnings regarding the ComponentData class. The model still runs smoothly, and the results are correct, but the warnings are now accumulating, which is why I wanted to get to the bottom of this. I noticed that I only get the warnings when I work with indexed values. Without indexed values, they do not appear.

Minimal Example with indexes values produce warnings

Here is a small minimal example:

import pyomo.environ as pyo

model = pyo.ConcreteModel()
model.s = pyo.Set(initialize=[1, 2, 3])  # with indexes = with warnings
model.v1 = pyo.Var(model.s, bounds=(0.1, 1.0))
model.v2 = pyo.Var(model.s, bounds=(0.2, 1.0))


def x_rule(m: pyo.Model, s: int):
    return m.v1[s] * m.v2[s]
model.x = pyo.Expression(model.s, rule=x_rule)

def objective(m: pyo.Model):
    return sum(m.x[s] for s in m.s)
model.obj = pyo.Objective(rule=objective)

pyo.SolverFactory("ipopt").solve(model)

In this example, PyCharm (version 2025.3) gives me the following warnings:

• In the x_rule (specifically for the multiplication operator “*”): "Class 'ComponentData' does not define '_mul_', so the '*' operator cannot be used on its instances"

• In the objective function (specifically for the code inside the sum function): "Unexpected type(s): Generator[ComponentData, Any, None]) Possible type(s): [...]"

Minimal Example without indexes values do not produce warnings

Here is a small minimal example without indexes values:

import pyomo.environ as pyo

model = pyo.ConcreteModel()
model.v1 = pyo.Var(bounds=(0.1, 1.0))
model.v2 = pyo.Var(bounds=(0.2, 1.0))


def x_rule(m: pyo.Model):
    return m.v1 * m.v2
model.x = pyo.Expression(rule=x_rule)

def objective(m: pyo.Model):
    return m.x
model.obj = pyo.Objective(rule=objective)

pyo.SolverFactory("ipopt").solve(model)

This is a very similar example, only without indexes, and I don't get any warnings here.

In both cases, I get the same results (just once for all three values of v1 and v2, and once for the single variable). My own project with significantly more variables (and unfortunately also more warnings...) also runs through and produces meaningful results.

Am I using the indexed values in the functions incorrectly or uncleanly, which is why I am getting these warnings, or is it due to “false positive” warnings that Pyomo sometimes issues? In a similar case (Why does PyCharm give me a warning when using Pyomo's .fix() method?), I also got warnings from Pyomo for functionalities that are described in their documentation as I use them and have probably not yet been smoothed out.

Thank you for your help and best regards!

Schicko