Cant Get a result form random.shuffle in python

Question

I have never had this problem before but when i try and shuffle a list i get a return of 'None'

import random
c=[1,4,67,3]
c=random.shuffle(c)
print c

The print statement returns 'None' and i dont know why, I have looked around for an answer to this problem but there doesent seem to be anything. I hope i am not making an obvious mistake.

Answer 1

The random.shuffle function sorts the list in-place, and to avoid causing confusion on that point, it doesn't return the shuffled list. Try just:

 random.shuffle(c)
 print(c)

This is a nice bit of API design, I think - it means that if you misunderstand what random.shuffle is doing, then you'll get a obvious problem immediately, rather than a more subtle bug that's difficult to track down later on...

Answer 2

Remember that random.shuffle() shuffles in-place. So it updates the object named “c”. But then you rebind “c” with None, the output of the function, and the list gets lost.

Answer 3

From the doc :

Shuffle the sequence x in place.

So

import random
c=[1,4,67,3]
random.shuffle(c)
print c

works as expected.

Answer 4

Try like this

import random c=[1,4,67,3] random.shuffle(c) print c