/usr/lib/python2.7/dist-packages/stdnum/damm.py is in python-stdnum 1.5-1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 | # damm.py - functions for performing the Damm checksum algorithm
#
# Copyright (C) 2016 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
"""The Damm algorithm.
The Damm algorithm is a check digit algorithm that should detect all
single-digit errors and all adjacent transposition errors. Based on
anti-symmetric quasigroup of order 10 it uses a substitution table.
This implementation uses the table from Wikipedia by default but a custom
table can be provided.
More information:
* https://en.wikipedia.org/wiki/Damm_algorithm
>>> validate('572')
Traceback (most recent call last):
...
InvalidChecksum: ...
>>> calc_check_digit('572')
'4'
>>> validate('5724')
'5724'
"""
from stdnum.exceptions import *
_operation_table = (
(0, 3, 1, 7, 5, 9, 8, 6, 4, 2),
(7, 0, 9, 2, 1, 5, 4, 8, 6, 3),
(4, 2, 0, 6, 8, 7, 1, 3, 5, 9),
(1, 7, 5, 0, 9, 8, 3, 4, 2, 6),
(6, 1, 2, 3, 0, 4, 5, 9, 7, 8),
(3, 6, 7, 4, 2, 0, 9, 5, 8, 1),
(5, 8, 6, 9, 7, 2, 0, 1, 3, 4),
(8, 9, 4, 5, 3, 6, 2, 0, 1, 7),
(9, 4, 3, 8, 6, 1, 7, 2, 0, 5),
(2, 5, 8, 1, 4, 3, 6, 7, 9, 0))
def checksum(number, table=None):
"""Calculate the Damm checksum over the provided number. The checksum is
returned as an integer value and should be 0 when valid."""
table = table or _operation_table
i = 0
for n in str(number):
i = table[i][int(n)]
return i
def validate(number, table=None):
"""Checks to see if the number provided passes the Damm algorithm."""
if not bool(number):
raise InvalidFormat()
try:
valid = checksum(number, table=table) == 0
except Exception:
raise InvalidFormat()
if not valid:
raise InvalidChecksum()
return number
def is_valid(number, table=None):
"""Checks to see if the number provided passes the Damm algorithm."""
try:
return bool(validate(number), table=table)
except ValidationError:
return False
def calc_check_digit(number, table=None):
"""With the provided number, calculate the extra digit that should be
appended to make it pass the Damm check."""
return str(checksum(number, table=table))
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