List comprehension list of lists
Solution 1:
Use this:
[[number+1 for number in group] for group in x]
Or use this if you know map:
[map(lambda x:x+1 ,group) for group in x]
Solution 2:
Starting from the structure of your data:
x = [[1,2,3],[4,5,6],[7,8,9]]
Every group is a triplet [a,b,c], so I consider for readability a solution like:
«take every group [a,b,c] from the list and provide me the list of [a+1,b+1,c+1] »
x_increased = [ [a+1,b+1,c+1] for [a,b,c] in x ]