slicing list of lists in Python

Question

I need to slice a list of lists in python.

A = [[1,2,3,4,5],[1,2,3,4,5],[1,2,3,4,5]]
idx = slice(0,4)
B = A[:][idx]

The code above isn\'t

Answer 1

With numpy it is very simple - you could just perform the slice:

In [1]: import numpy as np

In [2]: A = np.array([[1,2,3,4,5],[1,2,3,4,5],[1,2,3,4,5]])

In [3]: A[:,:3]
Out[3]: 
array([[1, 2, 3],
       [1, 2, 3],
       [1, 2, 3]])

You could, of course, transform numpy.array back to the list:

In [4]: A[:,:3].tolist()
Out[4]: [[1, 2, 3], [1, 2, 3], [1, 2, 3]]