Yes sample is choosing unique numbers

Have a look here

random.sample(population, k)

Return a k length list of unique elements chosen from the population sequence. Used for random sampling without replacement.

To choose a sample from a range of integers, use an range() object as an argument

>>> import random
>>> print random.sample(range(1,100),3)
[77, 29, 45]
>>> 

https://docs.python.org/2/library/random.html#random.sample