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# uid.py - functions for handling Swiss business identifiers
# coding: utf-8
#
# Copyright (C) 2015 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
"""UID (Unternehmens-Identifikationsnummer, Swiss business identifier).
The Swiss UID is used to uniquely identify businesses for taxation purposes.
The number consists of a fixed "CHE" prefix, followed by 9 digits that are
protected with a simple checksum.
This module only supports the "new" format that was introduced in 2011 which
completely replaced the "old" 6-digit format in 2014.
More information:
* https://www.uid.admin.ch/
* https://de.wikipedia.org/wiki/Unternehmens-Identifikationsnummer
>>> validate('CHE-100.155.212')
'CHE100155212'
>>> validate('CHE-100.155.213')
Traceback (most recent call last):
...
InvalidChecksum: ...
>>> format('CHE100155212')
'CHE-100.155.212'
"""
from stdnum.exceptions import *
from stdnum.util import clean, isdigits
def compact(number):
"""Convert the number to the minimal representation. This strips
surrounding whitespace and separators."""
return clean(number, ' -.').strip().upper()
def calc_check_digit(number):
"""Calculate the check digit for organisations. The number passed should
not have the check digit included."""
weights = (5, 4, 3, 2, 7, 6, 5, 4)
s = sum(w * int(n) for w, n in zip(weights, number))
return str((11 - s) % 11)
def validate(number):
"""Check if the number is a valid UID. This checks the length, formatting
and check digit."""
number = compact(number)
if len(number) != 12:
raise InvalidLength()
if not number.startswith('CHE'):
raise InvalidComponent()
if not isdigits(number[3:]):
raise InvalidFormat()
if number[-1] != calc_check_digit(number[3:-1]):
raise InvalidChecksum()
return number
def is_valid(number):
"""Check if the number is a valid UID."""
try:
return bool(validate(number))
except ValidationError:
return False
def format(number):
"""Reformat the number to the standard presentation format."""
number = compact(number)
return number[:3] + '-' + '.'.join(
number[i:i + 3] for i in range(3, len(number), 3))
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