Is there a short way to check uniqueness of values without using 'if' and multiple 'and's?

Question

I am writing some code and I need to compare some values. The point is that none of the variables should have the same value as another. For example:

a=1 b=2 c=3 if a != b and b != c and a != c:     #do something  

Now, it is easy to see that in a case of code with more variables, the if statement becomes very long and full of ands. Is there a short way to tell Python that no 2 variable values should be the same.

Answer 1

You can try making sets.

a, b, c = 1, 2, 3 if len({a,b,c}) == 3:    # Do something 

If your variables are kept as a list, it becomes even more simple:

a = [1,2,3,4,4] if len(set(a)) == len(a):     # Do something 

Here is the official documentation of python sets.

This works only for hashable objects such as integers, as given in the question. For non-hashable objects, see @chepner's more general solution.

This is definitely the way you should go for hashable objects, since it takes O(n) time for the number of objects n. The combinatorial method for non-hashable objects take O(n^2) time.

Answer 2

Assuming hashing is not an option, use itertools.combinations and all.

from itertools import combinations  if all(x != y for x, y in combinations([a,b,c], 2)):     # All values are unique