How to print the dual solutions?

[Swaprava Nath]

I have set up the primal LP in the model and solved the optimization using Gurobi. However, it is important to print the dual variables for my understanding. Can this be printed in Gurobi? If yes, then how? For the primal: I can call the primal variable (say k) as

k.getAttr('x')

But how to do it for duals (for which I don't know the variable names)?

Thanks,
Swaprava

[Renan Garcia]

Duals are constraint (not variable) attributes. In particular, you should use the Pi constraint attribute (see https://www.gurobi.com/documentation/6.5/refman/pi.html#attr:Pi).

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[Swaprava Nath]

Can you provide an example of getting the attribute?

I was tending to do: m.getConstr() which is not a right thing apparently.

[Renan Garcia]

Please see https://www.gurobi.com/documentation/6.5/refman/python_attribute_examples.html#PythonAttributeExamples for general guidance on querying attributes in Python. For example, you could use

  for c in m.getConstrs():

    print(c.pi)