problem in modeling "keyerror = 0"

Answered

Azmi Jundan Taqiy

November 25, 2021 04:45

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I got troubled with an error stating "KeyError = 0" on the model objective function

 

from gurobipy import *

# SET
RM = 7
RAW = range(RM) # index r
CE = 3
COMP = range(CE) # index c

# PARAMETER
PMIN_c = [2, 0.4, 1.2]
PMAX_c = [3, 0.6, 1.65]

P_rc = [[2.5, 0, 1.3],
[3, 0, 0.8],
[0, 0.3, 0],
[0, 90, 0],
[0, 96, 4],
[0, 0.4, 1.2],
[0, 0.6, 0]]

AVAIL_r = [400, 300, 600, 500, 200, 300, 250, 500]

COST_r = [200, 250, 150, 220, 240, 200, 165]

DEM = 500

# MODEL
m = Model()

# DECISION VARIABLE
use_r = m.addVars(RAW, COMP, vtype=GRB.CONTINUOUS, name="materials used")

# OBJECTIVE FUNCTION
m.setObjective(quicksum(COST_r[r] * use_r[r] for r in RAW), GRB.MINIMIZE)

0

• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  June 23, 2025 02:44 Edited

  This post is more than three years old. Some information may not be up to date. For current information, please check the Gurobi Documentation or Knowledge Base. If you need more help, please create a new post in the community forum. Or why not try our AI Gurobot?.
• 

  Jaromił Najman

  • Gurobi Staff

  November 26, 2021 09:05

  Your variables are defined over 2 lists \(\texttt{RAW}\) and \(\texttt{COMP}\). Thus, you have to access variables \(\texttt{use_r}\) via

  m.setObjective(quicksum(COST_r[r] * use_r[r,c] for r in RAW for c in COMP), GRB.MINIMIZE)

  Best regards,
  Jaromił

  0

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