old_contents: # vat.py - functions for handling Maltese VAT numbers
  #
  # Copyright (C) 2012 Arthur de Jong
  #
  # This library is free software; you can redistribute it and/or
  # modify it under the terms of the GNU Lesser General Public
  # License as published by the Free Software Foundation; either
  # version 2.1 of the License, or (at your option) any later version.
  #
  # This library 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
  # Lesser General Public License for more details.
  #
  # You should have received a copy of the GNU Lesser General Public
  # License along with this library; if not, write to the Free Software
  # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  # 02110-1301 USA
  
  """VAT (Maltese VAT number).
  
  The Maltese VAT registration number contains 8 digits and uses a simple
  weigted checksum.
  
  >>> compact('MT 1167-9112')
  '11679112'
  >>> is_valid('1167-9112')
  True
  >>> is_valid('1167-9113')  # invalid check digits
  False
  """
  
  from stdnum.util import clean
  
  
  def compact(number):
      """Convert the number to the minimal representation. This strips the
      number of any valid separators and removes surrounding whitespace."""
      number = clean(number, ' -').upper().strip()
      if number.startswith('MT'):
          number = number[2:]
      return number
  
  
  def checksum(number):
      """Calculate the checksum."""
      weights = (3, 4, 6, 7, 8, 9, 10, 1)
      return sum(weights[i] * int(n) for i, n in enumerate(number)) % 37
  
  
  def is_valid(number):
      """Checks to see if the number provided is a valid VAT number. This
      checks the length, formatting and check digit."""
      try:
          number = compact(number)
      except:
          return False
      return number.isdigit() and len(number) == 8 and \
             number[0] != '0' and checksum(number) == 0
  
new_contents: # vat.py - functions for handling Maltese VAT numbers
  #
  # Copyright (C) 2012, 2013 Arthur de Jong
  #
  # This library is free software; you can redistribute it and/or
  # modify it under the terms of the GNU Lesser General Public
  # License as published by the Free Software Foundation; either
  # version 2.1 of the License, or (at your option) any later version.
  #
  # This library 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
  # Lesser General Public License for more details.
  #
  # You should have received a copy of the GNU Lesser General Public
  # License along with this library; if not, write to the Free Software
  # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  # 02110-1301 USA
  
  """VAT (Maltese VAT number).
  
  The Maltese VAT registration number contains 8 digits and uses a simple
  weigted checksum.
  
  >>> validate('MT 1167-9112')
  '11679112'
  >>> validate('1167-9113')  # invalid check digits
  Traceback (most recent call last):
      ...
  InvalidChecksum: ...
  """
  
  from stdnum.exceptions import *
  from stdnum.util import clean
  
  
  def compact(number):
      """Convert the number to the minimal representation. This strips the
      number of any valid separators and removes surrounding whitespace."""
      number = clean(number, ' -').upper().strip()
      if number.startswith('MT'):
          number = number[2:]
      return number
  
  
  def checksum(number):
      """Calculate the checksum."""
      weights = (3, 4, 6, 7, 8, 9, 10, 1)
      return sum(weights[i] * int(n) for i, n in enumerate(number)) % 37
  
  
  def validate(number):
      """Checks to see if the number provided is a valid VAT number. This
      checks the length, formatting and check digit."""
      number = compact(number)
      if not number.isdigit() or number[0] == '0':
          raise InvalidFormat()
      if len(number) != 8:
          raise InvalidLength()
      if checksum(number) != 0:
          raise InvalidChecksum()
      return number
  
  
  def is_valid(number):
      """Checks to see if the number provided is a valid VAT number. This
      checks the length, formatting and check digit."""
      try:
          return bool(validate(number))
      except ValidationError:
          return False
  
subject: Implement validate() for Maltese numbers