text: # grid.py - functions for handling Global Release Identifier (GRid) numbers
  #
  # Copyright (C) 2010, 2011, 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
  
  """GRid (Global Release Identifier).
  
  The Global Release Identifier is used to identify releases of digital
  sound recordings and uses the ISO 7064 Mod 37, 36 algorithm to verify the
  correctness of the number.
  
  >>> validate('A12425GABC1234002M')
  'A12425GABC1234002M'
  >>> validate('Grid: A1-2425G-ABC1234002-M')
  'A12425GABC1234002M'
  >>> validate('A1-2425G-ABC1234002-Q') # incorrect check digit
  Traceback (most recent call last):
      ...
  InvalidChecksum: ...
  >>> compact('A1-2425G-ABC1234002-M')
  'A12425GABC1234002M'
  >>> format('A12425GABC1234002M')
  'A1-2425G-ABC1234002-M'
  """
  
  from stdnum.exceptions import *
  from stdnum.util import clean
  
  
  def compact(number):
      """Convert the GRid to the minimal representation. This strips the
      number of any valid separators and removes surrounding whitespace."""
      number = clean(number, ' -').strip().upper()
      if number.startswith('GRID:'):
          number = number[5:]
      return number
  
  
  def validate(number):
      """Check if the number is a valid GRid."""
      from stdnum.iso7064 import mod_37_36
      number = compact(number)
      if len(number) != 18:
          raise InvalidLength()
      return mod_37_36.validate(number)
  
  
  def is_valid(number):
      """Check if the number is a valid GRid."""
      try:
          return bool(validate(number))
      except ValidationError:
          return False
  
  
  def format(number, separator='-'):
      """Reformat the number to the standard presentation format."""
      number = compact(number)
      number = (number[0:2], number[2:7], number[7:17], number[17:])
      return separator.join(x for x in number if x)
  