Adding data to a nested list in Python

Question

I have a nested list e.g.:

nlist = [
         [1, 2, 3], 
         [4, 5, 6], 
         [7, 8, 9],
        ]

Before I insert this list into

Answer 1

Why not change the original list (if that is all you want to do):

for row in nlist:
    row.insert(0, a)

Answer 2

Iterate over your outer list. For each inner list use list method insert(0, new_data).

Answer 3

If you are looking to create a new list then this will work as well...

nlistnew = [[a]+row for row in nlist]

EDIT: Fixed code as per Felix Kling's comment. Thanks!