Generate a random list of numbers

[Seymore4Head]

Why does a work and b doesn't?  What I was trying to accomplish with b
is to get a random list (of random length) that could have digits
repeat.  

I got idea for both methods from the Internet.  I do see that one uses
brackets and the other doesn't, but I don't know the difference.

import random
for i in range (5):
    a = random.sample(range(10), random.randrange(3,6))
    print a

for i in range (5):    
    b = [random.randrange (10), random.randrange(4,8)]
    print b