88 lines
2.6 KiB
Python
88 lines
2.6 KiB
Python
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# rtn.py - functions for handling banking routing transit numbers
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#
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# Copyright (C) 2014 Lifealike Ltd
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#
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301 USA
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"""RTN (Routing transport number).
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The routing transport number is a nine digit number used in the US banking
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system for processing deposits between banks.
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The last digit is a checksum.
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>>> calc_check_digit('11100002')
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'5'
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>>> validate('111000025')
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'111000025'
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>>> validate('11100002') # Not nine digits
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Traceback (most recent call last):
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...
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InvalidLength: ..
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>>> validate('11100002B') # Not all numeric
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Traceback (most recent call last):
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...
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InvalidFormat: ..
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>>> validate('112000025') # bad checksum
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Traceback (most recent call last):
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...
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InvalidChecksum: ..
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"""
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from stdnum.exceptions import *
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from stdnum.util import clean
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def compact(number):
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"""Convert the number to the minimal representation. This strips the
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number of any surrounding whitespace."""
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number = clean(number).strip()
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return number
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def calc_check_digit(number):
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"""Calculate the check digit. The number passed should not have the
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check digit included."""
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digits = [int(c) for c in number]
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checksum = (
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7 * (digits[0] + digits[3] + digits[6]) +
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3 * (digits[1] + digits[4] + digits[7]) +
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9 * (digits[2] + digits[5])
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) % 10
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return str(checksum)
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def validate(number):
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"""Checks to see if the number provided is a valid routing number. This
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checks the length and check digit."""
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number = compact(number)
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if not number.isdigit():
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raise InvalidFormat()
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if len(number) != 9:
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raise InvalidLength()
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if calc_check_digit(number[:-1]) != number[-1]:
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raise InvalidChecksum()
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return number
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def is_valid(number):
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"""Checks to see if the number provided is a valid RTN. This checks the
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length and check digit."""
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try:
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return bool(validate(number))
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except ValidationError:
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return False
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