Define an objective

To set an objective for your optimization problem, assign an expression to either the .minimize or .maximize attribute of the Model. For example:

m.minimize = capital_costs + operating_costs

Note that the objective expression must be dimensionless (it makes no sense to have multiple objectives with different labels). You can use .sum() to collapse a dimensioned expression into a dimensionless one.

Define an objective incrementally

For larger models, it is often convenient to define the objective function incrementally. To do so, use the += operator:

m = pf.Model()
m.minimize = 0

# Later in your code
m.minimize += capital_costs

# Somewhere else in your code
m.minimize += operating_costs

Alternative approach

Alternatively, rather than use .minimize or .maximize, you can use .objective and define the direction using the sense argument during model creation:

m = pf.Model(sense="min")
m.objective = capital_costs + operating_costs

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