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

My solution. I can't speak to how efficient it is; I think it runs in n^2 time.

>>> def fst_nr(s):
...     collection = []
...     for i in range(len(s)):
...             if not s[i] in collection and not s[i] in s[i+1:]:
...                     return s[i]
...             else:
...                     collection+=[s[i]]
... 
>>> fst_nr("teeter")
'r'
>>> fst_nr("floccinaucinihilipilification")
'u'
>>> fst_nr("floccinacinihilipilification")
'h'
>>> fst_nr("floccinaciniilipilification")
'p'
>>> fst_nr("floccinaciniiliilification")
't'
>>> fst_nr("floccinaciniiliilificaion")
>>> 

Any advice for a humble Stack noob?