Modifying model data in amplpy with several indices

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Hi, I am moving my AMPL code to the module amplpy and I got stuck when modifying my model data, probably this is a simple question because I don’t have much expertise in python. So, what I need is to pass this assignment to amplpy:

let Vq_inc[t,d,h,j]:=1;

In https://amplpy.readthedocs.io/ I found examples when the parameter is not indexed (e.g. doing index.set_values([1]) and when it has one index (e.g., index.set_values({i:0})); thus, for my problem I tried:

Vq_inc.set_values({(t,d,h,j):1 for t in T for d in D for h in H for j in No})

but it doesn’t work. Please, help me with that issue.
Thanks in advance

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2

Hi @Jonathan,

Vq_inc.set_values({(t,d,h,j):1 for t in T for d in D for h in H for j in No}) seems correct. Was it giving some error?

The following snippet assigns a dictionary to a parameter with 4 indices:

ampl = AMPL()
ampl.eval('param p{1..10, 1..10, 1..10, 1..10};')
ampl.param['p'].set_values({(i, j, k, l): 1 for i in range(1, 10+1) for j in range(1, 10+1) for k in range(1, 10+1) for l in range(1, 10+1)})
ampl.display('p')

Note: For this case in particular, ampl.eval('let {t in ..., d in ..., h in ..., j in ...} Vq_inc[t,d,h,j] := 1;') (replacing ... by the corresponding sets if they exist in AMPL) would be the fastest way to perform this operation as it would avoid data transfer from Python completely.

3

Hi Filipe,
Thanks for your response. The error that I obtained with Vq_inc.set_values({(t,d,h,j):1 for t in T for d in D for h in H for j in No}) is TypeError: Failed to cast value to int/float/double/string. The suggested routine works well, but I would like to replace the ranges by their corresponding sets, and probably that is the cause of the error, since T, D, H and No are sets. Finally, the last method indicated in the note works very well, so I will use it, thanks for that.