Collection length checking before determining duplicate items

duplicate_perf.py

import timeit

NO_DUPLICATES = (
    'one', 'two', 'three', 'four', 'five', 'six',
    'seven', 'eight', 'nine', 'ten', 'eleven', 'twelve')
WITH_DUPLICATES = (
    'one', 'two', 'three', 'four', 'five', 'six',
    'seven', 'one', 'nine', 'two', 'eleven', 'three')


def check_length_first(collection):
    if len(collection) != len(set(collection)):
        return {x for x in collection if collection.count(x) > 1}


def immediate_duplicates(collection):
    return {x for x in collection if collection.count(x) > 1}


def seen_set_duplicates(collection):
  """Builds a set of unique entries, returns items already contained. O(n)"""
  seen = set()
  return {x for x in collection if x in seen or seen.add(x)}


def call_latency(collection):
  pass


if __name__ == '__main__':
    print 'Just the function calls: {}'.format(timeit.timeit(
        'call_latency(NO_DUPLICATES)',
        setup='from __main__ import call_latency, NO_DUPLICATES'))
    print '\nLength check first, no dupes: {}'.format(timeit.timeit(
        'check_length_first(NO_DUPLICATES)',
        setup='from __main__ import check_length_first, NO_DUPLICATES'))
    print 'Length check first, dupes: {}'.format(timeit.timeit(
        'check_length_first(WITH_DUPLICATES)',
        setup='from __main__ import check_length_first, WITH_DUPLICATES'))
    print '\nNo length check, no dupes: {}'.format(timeit.timeit(
        'immediate_duplicates(NO_DUPLICATES)',
        setup='from __main__ import immediate_duplicates, NO_DUPLICATES'))
    print 'No Length check, dupes: {}'.format(timeit.timeit(
        'immediate_duplicates(WITH_DUPLICATES)',
        setup='from __main__ import immediate_duplicates, WITH_DUPLICATES'))
    print '\nSeen-set based, no dupes: {}'.format(timeit.timeit(
        'seen_set_duplicates(NO_DUPLICATES)',
        setup='from __main__ import seen_set_duplicates, NO_DUPLICATES'))
    print 'Seen-set based, dupes: {}'.format(timeit.timeit(
        'seen_set_duplicates(WITH_DUPLICATES)',
        setup='from __main__ import seen_set_duplicates, WITH_DUPLICATES'))

# Example timings from a Core i5-6200U
# Just the function calls: 0.0743689537048

# Length check first, no dupes: 0.500941991806
# Length check first, dupes: 3.38291621208

# No length check, no dupes: 2.72766900063
# No Length check, dupes: 2.82286787033

# Seen-set based, no dupes: 1.60548996925
# Seen-set based, dupes: 1.44544911385