I know this is quite an old question -
A = [[1, 2, 3],
[4, 5, 6],
[7, 8, 9]]
Let's say, you want to extract the first 2 rows and first 3 columns
A_NEW = A[0:2, 0:3]
A_NEW = [[1, 2, 3],
[4, 5, 6]]
Understanding the syntax
A_NEW = A[start_index_row : stop_index_row,
start_index_column : stop_index_column)]
If one wants row 2 and column 2 and 3
A_NEW = A[1:2, 1:3]
Reference the numpy indexing and slicing article - Indexing & Slicing