Having trouble making a list of lists of a designated size [duplicate]

I am trying to make a list of lists of about 5000 lists and it keeps messing up.
right now I just do this:

array = [[]]*5000
for line in f2:
    a = line.split()
    grid = int(a[0])
    array[grid].append(a[1])

print Counter(array[0]).most_common(10)

the problem is when I make the counter it does it as if the whole array of lists was actually just one list. Is there something obvious that I am doing wrong? Thanks

Using [[]]*5000, you are creating 5000 reference to the same list in your outer list. So, if you modify any list, it will modify all of them.

You can get different lists like this:

a = [[] for _ in xrange(5000)]