penjee . com and non-pythonic code

[buran]

for me for number in numbers loop is the best and most pythonic in this case. while numbers is better than while len(numbers)>0, but still you still need to use pop() (inefficient compared to the for loop - it will make difference if long list, because you change and reindex the list with every iteration). if you HAVE TO, then use collections.deque, especially for long lists.
also I don't like comparison to 0.

key = 'odd' if num % 2 else 'even'

By the way, I don't like ternary conditional operator and use it only in really trivial cases (e.g. in this case it is OK).

numbers = [12, 37, 5, 42, 8, 3]
odd=[]
even=[]
for num in numbers:
    if num % 2:
        odd.append(num)
    else:
        even.append(num)

following is also nice, but maybe not that explicit

from collections import defaultdict
numbers = [12, 37, 5, 42, 8, 3]
separated = defaultdict(list)
for num in numbers:
    separated[num%2].append(num)