def _pad(self, s):
    return s + (self.bs - len(s) % self.bs) * chr(self.bs - len(s) % self.bs)

def _unpad(self, s):
    return s[:-ord(s[len(s)-1:])]

def _pad(self, s):
    amount_of_padding = self.bs - len(s) % self.bs   # between 1 and self.bs, inclusive
    padding_char = chr(amount_of_padding)            # encode amount_of_padding in ASCII!
    return s + amount_of_padding * padding_char      # do string repetition with *

def _unpad(self, s):
    padding_char = s[-1]                     # last char is always part of the padding
    amount_of_padding = ord(padding_char)    # decode amount from ASCII value of char
    return s[:-amount_of_padding]            # slice to skip padding chars