I would like to give some feedback about ...

From: http://www.checkio.org/mission/non-unique-elements/solve/

HTTP_USER_AGENT:

Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:33.0) Gecko/20100101 Firefox/33.0

When I ran:

def checkio(data): #Your code here #It's main function. Don't remove this function #It's used for auto-testing and must return a result for check.

#replace this for solution

for i in range(0, len(data)-1):
 if(data.count(data[i]) > 1):
    pass
 else:
    data.pop(i)
return data

x = [1, 2, 4, 2, 1, 3]

checkio(x) print x

on my linux it generates the correct output 1, 2, 2, 1 while when I use your system it generates 'Index out of range error'

Leo