python fast square root

1from ctypes import c_float, c_int32, cast, byref, POINTER
2
3def ctypes_isqrt(number):
4    threehalfs = 1.5
5    x2 = number * 0.5
6    y = c_float(number)
7
8    i = cast(byref(y), POINTER(c_int32)).contents.value
9    i = c_int32(0x5f3759df - (i >> 1))
10    y = cast(byref(i), POINTER(c_float)).contents.value
11
12    y = y * (1.5 - (x2 * y * y))
13    return y
14