Writing a Constraint using quicksum

Answered

Abhishek Bajpai

September 15, 2022 10:14

Hi team,

I am new to Gurobi.

I am using it for some cost optimisation.

Can someone guide me with writing this constraint?

i & t are the values inside my Variable list.

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Official comment
Simranjit Kaur

Gurobi Staff

November 16, 2025 23:28
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Jaromił Najman

Gurobi Staff

September 15, 2022 10:55 Edited
One way would be
```
import gurobipy as gp
from gurobipy import GRB

T = list(range(0,10))
I = list(range(0,10))

m = gp.Model()

N = m.addVars(I,T)

constraints = m.addConstrs((gp.quicksum(N[i,t] for t in T) == 1 for i in I), name="constraint")
```
Here are a few good resources to get you started with nested summations:
- Python I: Introduction to Modeling with Python - Gurobi. This is your best place to start. It includes a video tutorial and examples with jupyter notebooks for you to follow. It also includes an example of using nested summations.
- netflow.py: This is a Gurobi example of how to do nested summations in two different ways: (a) using quicksum and (b) using tupledict.sum()
- quicksum() documentation
Best regards,
Jaromił
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