Pyomo default parameters

default_params.py

"""Looking parameter defaults based on another parameter in Pyomo.

We have a model described as:

min sum(x * Y[s] for s in S)

Where Y[s] has a default value of x if not supplied.
"""
import pyomo.environ as pyo

if __name__ == "__main__":
    model = pyo.AbstractModel()
    # S is our set which indexes Y
    model.S = pyo.Set()

    # x is a scalar param, and our default value.    
    model.x = pyo.Param(domain=pyo.Reals)
    # Y is our vector param which defaults to x if there is any missing data.
    model.Y = pyo.Param(model.S, default=lambda model, s: model.x)

    def objective(model):
        return pyo.quicksum(model.x * model.Y[s] for s in model.S)

    model.obj = pyo.Objective(rule=objective)

    solver = pyo.SolverFactory("glpk")

    instance = model.create_instance({None: {"S": [1, 2], "x": {None: 2.0}, "Y": {1: 10.0}}})
    solver.solve(instance).write()
    # 24.0

    instance = model.create_instance({None: {"S": [1, 2], "x": {None: 2.0}}})
    solver.solve(instance).write()
    # 8.0

    instance = model.create_instance({None: {"S": [1, 2], "x": {None: 2.0}, "Y": {1: -2}}})
    solver.solve(instance).write()
    # 0.0