convert single list(flatten list) to double list

Question

I have a list like this:

df = ['1 90 80', '2 70 50', '3 60 60']

and I want to convert the list like this:

result = [[1, 90, 80], [2, 70, 50], [3, 60, 60]]

I tried with for loop and append() function, but I found that I can not append list as it is.

Is there any way to solve this? Thanks