TypeError when using gurobipy.Model.addGenConstrIndicator
AnsweredHi,
I am encountering a problem with a logical constraint. I get the same error when trying ".addGenConstrIndicator". I posted the code below including the error message. I am grateful for any kind of help. Note that this is a test case because I encountered problems in my main model applying a similar logic. The overall goal is to indicate (finish = 1) when beets are finished (beet = 0).
Thank you!
from gurobipy import Model, GRB, quicksum
# Define the sets I and T
I = [1, 2]
T = [0, 1, 2, 3, 4]
# Create a new Gurobi model
model = Model("test_model")
# Define fixed beet_flow values
beet_flow = {
(1, 0, 0, 0): 1500.0,
(1, 0, 0, 1): 5.1,
(1, 0, 0, 2): 5.0,
(1, 0, 0, 3): 0.0,
(1, 0, 0, 4): 0.0,
(2, 0, 0, 0): 100.5,
(2, 0, 0, 1): 10.1,
(2, 0, 0, 2): 10.0,
(2, 0, 0, 3): 10.0,
(2, 0, 0, 4): 0.0
}
finish = model.addVars(I, T, vtype=GRB.BINARY, name="finish")
# Ensure the 'finish' variable is 1 when beets are 0 using indicator constraints
for i in I:
for t in T:
beet = (beet_flow[i, 0, 0, t])
model.addConstr((finish[i, t] == 1) >> (beet <= 1))
# Optimize the model
model.optimize()
# Check and print the results
if model.status == GRB.OPTIMAL:
for i in I:
for t in T:
print(f"finish[{i},{t}] = {finish[i, t].x}")
print(f"Beets [{i}, {t}]: {beet_flow[i,0,0,t]}")
Output:
Traceback (most recent call last):
File "/Users/...", line 36, in <module>
model.addConstr((finish[i, t] == 1) >> (beet <= 1))
File "src/gurobipy/model.pxi", line 3637, in gurobipy.Model.addConstr
File "src/gurobipy/model.pxi", line 4714, in gurobipy.Model.addGenConstrIndicator
TypeError: unsupported operand type(s) for =: 'NoneType' and 'float'

Hi Ludwig,
it seems that "beet" is not a variable, so you also cannot use it to construct the constraint "beet <= 1". You may have to add another call to addVariable() to do something with those beet values.
I hope that helps.
Cheers,
Matthias1 
Thank you that solved the problem
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