89 lines
2.8 KiB
Python
89 lines
2.8 KiB
Python
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# cusip.py - functions for handling CUSIP numbers
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#
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# Copyright (C) 2015 Arthur de Jong
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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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"""CUSIP number (financial security identification number).
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CUSIP (Committee on Uniform Securities Identification Procedures) numbers are
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used to identify financial securities. CUSIP numbers are a nine-character
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alphanumeric code where the first six characters identify the issuer,
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followed by two digits that identify and a check digit.
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More information:
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https://en.wikipedia.org/wiki/CUSIP
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https://www.cusip.com/
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>>> validate('DUS0421C5')
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'DUS0421C5'
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>>> validate('DUS0421CN')
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Traceback (most recent call last):
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...
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InvalidChecksum: ...
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>>> to_isin('91324PAE2')
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'US91324PAE25'
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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 valid separators and removes surrounding whitespace."""
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return clean(number, ' ').strip().upper()
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# O and I are not valid but are accounted for in the check digit calculation
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_alphabet = '0123456789ABCDEFGH JKLMN PQRSTUVWXYZ*@#'
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def calc_check_digit(number):
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"""Calculate the check digits for the number."""
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# convert to numeric first, then sum individual digits
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number = ''.join(
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str((i % 2 + 1) * _alphabet.index(n)) for i, n in enumerate(number))
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return str((10 - sum(int(n) for n in number)) % 10)
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def validate(number):
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"""Checks to see if the number provided is valid. This checks the length
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and check digit."""
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number = compact(number)
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if not all(x in _alphabet for x in number):
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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 valid. This checks the length
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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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def to_isin(number):
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"""Convert the number to an ISIN."""
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from stdnum import isin
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return isin.from_natid('US', number)
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