Extending piecwise to 2 variables (or a variable and a parameter)

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score can only be evaluated in the integers $0, 1, 2,...,\mathtt{ncand}-1$ and, in fact, $\mathtt{score}(i)=\mathtt{ncand}-i$. Is it intended? Anyway, if you have something like

ncand = some value
score = piecewise(list of cases depending on ncand)

you can redefine score to depend on ncand as follows:

def score(x,ncand):
    s = piecewise(list of cases depending on ncand)
    return s(x)

Juanjo it was intended

But you answer is not self evident. Even short it ananswer not a comment.

I have transformed my comment into an answer.