Less (?) elegant way of finding empty indices of source list, using itertools

find_empties2.py

import random
from itertools import compress, count

# Initial list of references
source = [0, 1, 3, 4, 0, 5, 7, 0]
print source

# Build list of indices of source where content is zero
empty = compress(count(), [not x for x in source])
emptylist = list(empty)
print emptylist

# Select one of those indices at random
select = random.choice(emptylist)
print select

# Assign a value to the previously-empty element of the source list
source[select] = "TADA!"
print source