def f(t):
    (x, y, z, w) = t
    return x * y + z - w

def specialiser(f, constantes, positions):

    v = [0]*(len(t) + len(constantes))
    for i,c in zip(positions, constantes):
        v[i] = c
    variables_pos = [i for i in range(len(v)) if i not in positions]

    def specialisee(t):
        for i,p in enumerate(variables_pos):
            v[p] = t[i]
        return f(tuple(v))

    return specialisee


# On specialise f sur x et y (position 0 et 1) aux valeurs 5 et 6
g = specialiser(f, (5, 6), (0, 1))
optimise.minimize(g, [12.1, 121.5])