TypeError: object of type 'gurobipy.LinExpr' has no len()

[s.sch...@gmail.com]

Hi,

in my optimization code I get the error:

"TypeError: object of type 'gurobipy.LinExpr' has no len()"

I enclosed the full code in the appendix.

Does anyone know a solution to the problem?

[Robert Luce]

The error message is indeed a bit cryptic, but looking at the line

38: m.addConstrs((e[(p,t)] == max_((s[(p,t-1)] - s[(p,t)]), 0.0) for p in processsteps for t in range(1,T)), name="process_end")

I see that you are trying to feed an LinExpr object s[(p,t-1)] - s[(p,t)] into the max_ function, causing the error.  You can only pass in a list of variables as arguments for the max, see




http://www.gurobi.com/documentation/8.1/refman/py_max_.html




You could simply define auxiliary variables for each sum  s[(p,t-1)] - s[(p,t)], and use these variables as arguments for the max_ function.


Robert

[Sascha Scheef]

Thank you very much!

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