Normalizing A Vector

[Terry Reedy]

On 7/30/2010 7:46 AM, Lawrence D'Oliveiro wrote:
> Say a vector V is a tuple of 3 numbers, not all zero. You want to normalize
> it (scale all components by the same factor) so its magnitude is 1.
>
> The usual way is something like this:
>
>      L = math.sqrt(V[0] * V[0] + V[1] * V[1] + V[2] * V[2])
>      V = (V[0] / L, V[1] / L, V[2] / L)
>
> What I don’t like is having that intermediate variable L leftover after the
> computation.

So, instead of fooling around with error-prone, hard-to-type 
constructions, just delete the damn thing!

def L

Compare those foolproof 5 chars to what at first did not work right and 
even what did.  And, as other said, in most real applications, you will 
normalize in more than one place. In fact, you may well want a vlen 
function.

def vlen(seq): return math.sqrt(sum(x*x for x in seq))

-- 
Terry Jan Reedy