Iteration over recursion?

[MTD]

Hello all,

I've been messing about for fun creating a trial division factorizing
function and I'm naturally interested in optimising it as much as
possible.

I've been told that iteration in python is generally more
time-efficient than recursion. Is that true?

Here is my algorithm as it stands. Any suggestions appreciated!

from math import *

def factorize(x):
    """ Return factors of x """
    factors = []
    lim = int(sqrt(x))
    y = divmod(x,2)
    if y[1] == 0: # x is even
        factors = factors + [2] + factorize(y[0])
    else:   # x is odd
        i = 3
        while i <= lim:
            y = divmod(x,i)
            if y[1] == 0:
                factors = factors + [i] + factorize(y[0])
                i = lim+1
            else:
                i += 2

    if factors == []: # necessary step for correct recursion
        factors = [x]
        
    return factors