What is the difference between random.sample and random.shuffle in Python

Question

I have a list a_tot with 1500 elements and I would like to divide this list into two lists in a random way. List a_1 would have 1300 and list a_2 would have 200 elements. My

Answer 1

There are two major differences between shuffle() and sample():

1) Shuffle will alter data in-place, so its input must be a mutable sequence. In contrast, sample produces a new list and its input can be much more varied (tuple, string, xrange, bytearray, set, etc).

2) Sample lets you potentially do less work (i.e. a partial shuffle).

It is interesting to show the conceptual relationships between the two by demonstrating that is would have been possible to implement shuffle() in terms of sample():

def shuffle(p):
   p[:] = sample(p, len(p))

Or vice-versa, implementing sample() in terms of shuffle():

def sample(p, k):
   p = list(p)
   shuffle(p)
   return p[:k]

Neither of these are as efficient at the real implementation of shuffle() and sample() but it does show their conceptual relationships.