Feedback from user Columpio
http://www.checkio.org/mission/common-words
Right solution, bad tests (doesn't pass).
def checkio(first, second):
    from operator import and_
    return ",".join(and_(*map(lambda x: set(x.split(',')), (first, second))))
"""
 Your result: "two,one,three"
Right result: "one,three,two"
Fail: checkio("one,two,three", "four,five,one,two,six,three")
"""
Where's difference between mine and right?
URL from: http://www.checkio.org/mission/common-words/solve/
HTTP_USER_AGENT: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/35.0.1916.114 Safari/537.36
Right solution, bad tests (doesn't pass).
def checkio(first, second):
    from operator import and_
    return ",".join(and_(*map(lambda x: set(x.split(',')), (first, second))))
"""
 Your result: "two,one,three"
Right result: "one,three,two"
Fail: checkio("one,two,three", "four,five,one,two,six,three")
"""
Where's difference between mine and right?
URL from: http://www.checkio.org/mission/common-words/solve/
HTTP_USER_AGENT: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/35.0.1916.114 Safari/537.36