def _dpow(x, y, n):
    if n < 0:
        raise ValueError("invalid derivative order")
    elif n > y:
        return 0
    else:
        return poch(y - n + 1, n) * x**(y - n)
d^n (x**y) / dx^n
dataset/ETHPy150Open scipy/scipy/scipy/interpolate/tests/test_interpolate.py/_dpow