from scipy.interpolate import LinearNDInterpolator as LND

Ddump = pd.read_csv('C:....csv', header='infer', low_memory=False, dtype = np.float64)

X = Ddump.iloc[:,:4].values
Y = Ddump.iloc[:,4:].values

hull={}
List = Ddump.iloc[:,4:].head().columns.to_list()
for i in range(Y.shape[1]):
Fit = LND(X,Y[:,i])
hull[List[i].format(i)] = Fit

Set = 'S19'
PVec = np.array([0.1111 , 67.42, -.22, 1.97])

[in]  hull[Set](PVec)
[out] array([2179.0411926])

@xw.func
@xw.arg('Set', str)
@xw.arg('Prices', np.array, ndim=2)
def LND(Set,Prices):
    return hull[Set](Prices)