Python fast square root

python fast square root

from ctypes import c_float, c_int32, cast, byref, POINTER

def ctypes_isqrt(number):
    threehalfs = 1.5
    x2 = number * 0.5
    y = c_float(number)

    i = cast(byref(y), POINTER(c_int32)).contents.value
    i = c_int32(0x5f3759df - (i >> 1))
    y = cast(byref(i), POINTER(c_float)).contents.value

    y = y * (1.5 - (x2 * y * y))
    return y