Find the first non-repeated character in a string

Question

I read of a job interview question to write some code for the following:

Write an efficient function to find the first nonrepeated character in a st

Answer 1

def non_repeating(given_string):
    try:
        item = [x for x in given_string[:] if given_string[:].count(x) == 1][0]
    except:
        return None
    else:
        return item

# NOTE: The following input values will be used for testing your solution.
print non_repeating("abcab") # should return 'c'
print non_repeating("abab") # should return None
print non_repeating("aabbbc") # should return 'c'
print non_repeating("aabbdbc") # should return 'd'