Google Foobar Level 1 - Minion Task Schedule
if len(data) &gt; 99:
    exit('List contains more than 100 elements')

I'd change that error message to something like 'List contains a hundred or more elements'. I might also raise a ValueError instead of calling exit. I think that's more appropriate for an error that the user may want to catch.

You can get rid of your call to setdefault by using a defaultdict instead:
from collections import defaultdict

. . .

count = defaultdict(int)  # int is a function that returns 0 when no args are given to it
for i in data:
    count[i] += 1

The gain here isn't huge, but they're handy in many cases.
collections.Counter would probably be appropriate here as well, but I've only used it once, so I can't show a good example of it.