numpy col slicing

This is the code

import sys
import math
import numpy as np


def encryption(a):
    square=[]
    #a="if man was meant to stay on the ground god would have given us roots"
    a=a.replace(" ","")
    cols=int(math.sqrt(len(a)))
    rows=round(len(a)/cols)
    a=a+" "*int(cols-len(a)%cols)

    sq=np.reshape(np.array(list(a)),(rows,cols))

    s=""
    for n in range(cols-1):
        s=s+"".join(sq[:,n])+" "
    return s

To slice the array

2darray[:,2]

The : means each Row ,2 Col number 2