Restriction on gurobipy problem

Question

The main problem is the optimization of the filling of a tank, filling it in cheap periods and extracting in expensive periods to sell. I am using Python and gurobipy.

I am not able to model this constraint: the daily injection should be less than an expression depending on the previous day's filling.

\begin{align}X_i&\le C_i*(\sum_{j=0}^{j=i-1} X_j )\end{align}

I have tried with this expression:

m.addConstrs((x[i]<= C[i]*v1) for i in index)    
v1=sum(x[j] for j in range(1,i-1))

But it does not work. Note that $C_i$ is a constant.

Answer 1

Try

m.addConstrs(x[i] <= C[i] * sum(x[j] for j in range(i)) for i in index)

Python's range(n) yields an iterator from 0 to n-1. I also think that defining v1 after the constraint won't work (moreover, i ist not known to v1) and even if, I think the code becomes more legible if you avoid this.