Constraint Programming
OpenHi, i need to program this constraint and i have this code line:

As the error suggests, your code attempts to access variable \(\texttt{X[0, 25, 0]}\), which does not exist. I suspect the issue is as follows:
 The outer \(\texttt{for}\) loop of the \(\texttt{R4}\) constraints iterates over \( \texttt{t} \) in \(\texttt{range(1, len(T)  2)}\). Consequently, a constraint will be added for \( \texttt{t = len(T)  3} \).
 The inner \(\texttt{for}\) loop sums over \(\texttt{X[e, t_prima, s]}\) for \(\texttt{t_prima} = \texttt{t}\), \(\texttt{t+1}\), \(\texttt{t+2}\), and \(\texttt{t+3}\). When \( \texttt{t = len(T)  3} \), this means the code attempts to access \(\texttt{x[e, len(T), s]}\), which does not exist in Python's zerobased indexing.
Try changing your outer \(\texttt{for}\) loop to stop at \( \texttt{t} = \texttt{len(T)  4} \):
for t in range(1, len(T)  3)
(EDIT: or possibly \(\texttt{range(len(T)  3)}\), as Michel suggests below.)
Once the code is working, you can inspect the model for correctness by writing an LP file to disk with Model.write():
model.write("model.lp")
Lastly, the mathematical formulation of the constraint isn't totally clear. There are constraints for all \( t \in \{1, \ldots, T3\} \), but \( t \) is also used as the summation index in the constraint. From your code, it looks like the summation should instead sum over \(t'\): \( \sum_{t'=t}^{t+3} x_{e,t,s} \leq 3 \).
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It seems to me like there is a small confusion between the modelling (1indexed) and the code (python is 0indexed). It might make more sense to use range(0, len(T)3) in your constraint.
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