addGenConstrMax:'gurobipy.LinExpr' object has no attribute '__cindex__'

Answered

Yutong Zhang

November 27, 2022 09:15

I was trying to add a constraint as following:

for i in demand_list:
    maxVarsList = [data1.loc[i,j]*x[j] for j in truck_list]
    m.addGenConstrMax(sum(z[i,j] for j in truck_list), maxVarsList)

note: x[j] is a binary decision variable, z[i,j] is a decision variable, data1.loc[i,j] is a given variable.

AttributeError: 'gurobipy.LinExpr' object has no attribute '__cindex__'

How to add this max constraint correctly?

Related to

• General Constraints

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  Jonasz Staszek

  • Community Moderator

  November 28, 2022 07:08

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  Dear Yutong,

  could you please share a minimal reproducible example of the code which throws the error you mention?

  Best regards
  Jonasz

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  Jaromił Najman

  • Gurobi Staff

  November 28, 2022 09:37

  Dear Yutong,

  On top of providing a minimal reproducible example as noted by Jonasz, please note that the addGenConstrMax method does not accept an expression as its input. You have to provide a single optimization variable as first argument. Thus, you have to introduce an auxiliary variable \(aux\) and add the auxiliary equality constraint \(aux = \sum z_{ij}\), \(aux = \max(\dots)\).

  Best regards, 
  Jaromił

  0

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