Implementation of a custom non-punctuated and purely alphabetic string object.

alpha_string.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
#  pure_string.py
#  
#  Copyright 2015 Ericson Willians (Rederick Deathwill) <EricsonWRP@ERICSONWRP-PC>
#  
#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; either version 2 of the License, or
#  (at your option) any later version.
#  
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#  
#  You should have received a copy of the GNU General Public License
#  along with this program; if not, write to the Free Software
#  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
#  MA 02110-1301, USA.
#  
#  
 
from string import ascii_letters
 
class astr(str):
       
        """
        astr is a custom non-punctuated and purely alphabetic string
        that returns a string of zeros if an impure string is provided.
        """
       
        def __new__(self, content):
                if (lambda s: True if False not in [False for c in s if c not in ascii_letters] else False)(content):
                        return str.__new__(self, content)
                else:
                        return str.__new__(self, ''.join([str(0) for c in content]))
 
if __name__ == '__main__':

        x = astr("Normalstring")
        y = astr("alphanumeric7234852fsd36asd4fgh232")
        z = astr("Ácçènts")

        print(x)
        print(y)
        print(z)