Various ways to test if all members of a collection are unique in Python 2.7, with timing harness.

unique.py

import re
import array
import collections
import bisect

re_dup_g = re.compile(r'(.).*\1', re.DOTALL)
re_dup_ng = re.compile(r'(.).*?\1', re.DOTALL)


def isunique_reg(s, search=re_dup_g.search):
    return search(s) is None

def isunique_reng(s, search=re_dup_ng.search):
    return search(s) is None

def isunique_set(s, set=set, len=len):
    return len(s) == len(set(s))

def isunique_forset(s, set=set):
    seen = set()
    add = seen.add
    for c in s:
        if c in seen:
            return False
        add(c)
    return True

def isunique_array(s, array=array.array):
    seen = array('u')
    append = seen.append
    for c in s:
        if c in seen:
            return False
        append(c)
    return True

def isunique_deque(s, deque=collections.deque):
    seen = deque()
    append = seen.append
    for c in s:
        if c in seen:
            return False
        append(c)
    return True

def isunique_bisect(s, find=bisect.bisect_right, array=array.array):
    seen = array('u')
    insert = seen.insert
    for c in s:
        i = find(seen, c)
        if i and seen[i-1] == c:
            return False
        insert(i, c)
    return True

def isunique_bisectl(s, find=bisect.bisect_right):
    seen = []
    insert = seen.insert
    for c in s:
        i = find(seen, c)
        if i and seen[i-1] == c:
            return False
        insert(i, c)
    return True

def isunique_count(s, Counter=collections.Counter):
    return Counter(s).most_common(1)[0][1]==1

def isunique_list(s):
    seen = []
    append = seen.append
    for c in s:
        if c in seen:
            return False
        append(c)
    return True


def _test():
    funcs = [f for n,f in globals().items() if n.startswith('isunique_')]
    cases = [
        (u'string given', False),
        (u'string uoqzd', True),
    ]
    for func in funcs:
        for s,rv in cases:
            try:
                assert rv is func(s)
            except AssertionError, e:
                print "%s(%r) is not %r" % (func.__name__, s, rv)
                raise e

def _time():
    import timeit
    funcs = [f for n,f in globals().items() if n.startswith('isunique_')]
    funcs.sort(key=lambda f: f.__name__)
    cases = [
        ('!uniq', u'string given', False),
        ('uniq', u'string uoqzd', True),
    ]
    
    casenames = [name for name, _, _ in cases]
    fwidth = max(len(f.__name__) for f in funcs)
    timeitsetup = 's = {!r}; from __main__ import {} as u'
    
    print('{: <{fwidth}s}|{: >15s}|{: >15s}'.format('func', *casenames, fwidth=fwidth))
    print('-'*(fwidth+2+15+15))
    for f in funcs:
        times = [timeit.timeit('u(s)', setup=timeitsetup.format(input, f.__name__)) for _, input, _ in cases]
        print('{: <{fwidth}s}|{: >15.10f}|{: >15.10f}'.format(f.__name__, *times, fwidth=fwidth))

if __name__=='__main__':
    _test()
    _time()