Python Memory Model

I have a very large list Suppose I do that (yeah, I know the code is very unpythonic, but for the example's sake..):

n = (2**32)**2
for i in xrange(10**7)
  li[i] = n

works fine. however:

for i in xrange(10**7)
  li[i] = i**2

consumes a significantly larger amount of memory. I don't understand why that is - storing the big number takes more bits, and in Java, the the second option is indeed more memory-efficient...

Does anyone have an explanation for this?