ThinkPython2/code/has_duplicates.py at master · ProgrammerHuang/ThinkPython2 · GitHub

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"""This module contains a code example related to

Think Python, 2nd Edition
by Allen Downey
http://thinkpython2.com

Copyright 2015 Allen Downey

License: http://creativecommons.org/licenses/by/4.0/
"""

from __future__ import print_function, division


def has_duplicates(t):
    """Checks whether any element appears more than once in a sequence.

    Simple version using a for loop.

    t: sequence
    """
    d = {}
    for x in t:
        if x in d:
            return True
        d[x] = True
    return False


def has_duplicates2(t):
    """Checks whether any element appears more than once in a sequence.

    Faster version using a set.

    t: sequence
    """
    return len(set(t)) < len(t)


if __name__ == '__main__':
    t = [1, 2, 3]
    print(has_duplicates(t))
    t.append(1)
    print(has_duplicates(t))

    t = [1, 2, 3]
    print(has_duplicates2(t))
    t.append(1)
    print(has_duplicates2(t))