15. Add Border

Task

Given a rectangular matrix of characters, add a border of asterisks(*) to it.

Example

For

picture = ["abc",
           "ded"]

the output should be

addBorder(picture) = ["*****",
                      "*abc*",
                      "*ded*",
                      "*****"]

Input/Output

• [execution time limit]
  4 seconds (py3)

• [input] array.string picture
  A non-empty array of non-empty equal-length strings.
  Guaranteed constraints: 1 ≤ picture.length ≤ 100, 1 ≤ picture[i].length ≤ 100.

• [output] array.string
  The same matrix of characters, framed with a border of asterisks of width 1.

My Solution

def addBorder(picture):
    border = ['*' + element + '*' for element in picture]
    border.insert(0, '*' * (len(picture[0]) + 2))
    border.append('*' * (len(picture[0]) + 2))
    return border