Python3: String Reordering

Introduction

Kata – https://www.codewars.com/kata/string-reordering/train/python

Instructions

The input will be an array of dictionaries.

Return the values as a string-seperated sentence in the order of their keys’ integer equivalent (increasing order).

The keys are not reoccurring and their range is -999 < key < 999. The dictionaries’ keys & values will always be strings and will always not be empty.

Example

Input:
List = [
        {'4': 'dog' }, {'2': 'took'}, {'3': 'his'},
        {'-2': 'Vatsan'}, {'5': 'for'}, {'6': 'a'}, {'12': 'spin'}
       ]
Output:
'Vatsan took his dog for a spin'

My Solution

def sentence(List):
    return ' '.join([list(a.items())[0][1] for a in sorted(List, key=lambda k: int(list(k.items())[0][0]))])