Checking if all elements in a list are unique

python algorithm list unique
user225312 picture user225312 · Mar 11, 2011 · Viewed 90.8k times · Source

What is the best way (best as in the conventional way) of checking whether all elements in a list are unique?

My current approach using a Counter is:

>>> x = [1, 1, 1, 2, 3, 4, 5, 6, 2]
>>> counter = Counter(x)
>>> for values in counter.itervalues():
        if values > 1: 
            # do something

Can I do better?

Answer

yan picture yan · Mar 11, 2011

Not the most efficient, but straight forward and concise:

if len(x) > len(set(x)):
   pass # do something

Probably won't make much of a difference for short lists.

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