Discussion on: Whiteboarding in Python: Can You Solve This Simple String Problem?

[Jason C. McDonald]

Another approach, throwing out the "no other data structures" rule, is to strip the string down to letters-only, convert to a set, and compare lengths:

def unique_only(s):
    s = ''.join(c.lower() for c in s if c.isalpha())
    return len(set(s)) == len(s)

unique_only("My and his bot")  # True
unique_only("These are some words")  # False