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# bankaccount.py - functions for handling Czech bank account numbers
# coding: utf-8
#
# Copyright (C) 2022 Petr Přikryl
#
# 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
"""Czech bank account number.
The Czech bank account numbers consist of up to 20 digits:
UUUUUK-MMMMMMMMKM/XXXX
The first part is prefix that is up to 6 digits. The following part is from 2 to 10 digits.
Both parts could be filled with zeros from left if missing.
The final 4 digits represent the bank code.
More information:
* https://www.penize.cz/osobni-ucty/424173-tajemstvi-cisla-uctu-klicem-pro-banky-je-11
* https://www.zlatakoruna.info/zpravy/ucty/cislo-uctu-v-cr
>>> validate('34278-0727558021/0100')
'034278-0727558021/0100'
>>> validate('4278-727558021/0100') # invalid check digits (prefix)
Traceback (most recent call last):
...
InvalidChecksum: ...
>>> validate('34278-727558021/0000') # invalid bank
Traceback (most recent call last):
...
InvalidComponent: ...
>>> format('34278-727558021/0100')
'034278-0727558021/0100'
>>> to_bic('34278-727558021/0100')
'KOMBCZPP'
"""
from __future__ import annotations
import re
from stdnum.exceptions import *
from stdnum.util import clean
_bankaccount_re = re.compile(
r'((?P<prefix>[0-9]{0,6})-)?(?P<root>[0-9]{2,10})\/(?P<bank>[0-9]{4})')
def compact(number: str) -> str:
"""Convert the number to the minimal representation. This strips the
number of any valid separators and removes surrounding whitespace."""
number = clean(number).strip()
match = _bankaccount_re.match(number)
if match:
# zero-pad valid numbers
prefix = (match.group('prefix') or '').zfill(6)
root = match.group('root').zfill(10)
number = ''.join((prefix, '-', root, '/', match.group('bank')))
return number
def _split(number: str) -> tuple[str | None, str, str]:
"""Split valid numbers into prefix, root and bank parts of the number."""
match = _bankaccount_re.match(number)
if not match:
raise InvalidFormat()
return match.group('prefix'), match.group('root'), match.group('bank')
def _info(bank: str) -> dict[str, str]:
"""Look up information for the bank."""
from stdnum import numdb
info = {}
for _nr, found in numdb.get('cz/banks').info(bank):
info.update(found)
return info
def info(number: str) -> dict[str, str]:
"""Return a dictionary of data about the supplied number. This typically
returns the name of the bank and branch and a BIC if it is valid."""
prefix, root, bank = _split(compact(number))
return _info(bank)
def to_bic(number: str) -> str | None:
"""Return the BIC for the bank that this number refers to."""
return info(number).get('bic')
def _calc_checksum(number: str) -> int:
weights = (6, 3, 7, 9, 10, 5, 8, 4, 2, 1)
return sum(w * int(n) for w, n in zip(weights, number.zfill(10))) % 11
def validate(number: str) -> str:
"""Check if the number provided is a valid bank account number."""
number = compact(number)
prefix, root, bank = _split(number)
# guaranteed to be present because compacts adds a missing prefix
assert prefix
if _calc_checksum(prefix) != 0:
raise InvalidChecksum()
if _calc_checksum(root) != 0:
raise InvalidChecksum()
if 'bank' not in _info(bank):
raise InvalidComponent()
return number
def is_valid(number: str) -> bool:
"""Check if the number provided is a valid bank account number."""
try:
return bool(validate(number))
except ValidationError:
return False
def format(number: str) -> str:
"""Reformat the number to the standard presentation format."""
return compact(number)
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