IBAN.generate not working for DK ?

[AriMaritano]

Hey, thanks a lot for the library, it's been of huge help! :)

I'm not sure if there's a bug here or if I'm using schiwfty.IBAN.generate wrong for DK bank account. I check the specs for DK IBAN on swift, and they use '00400440116243' as an example. If I'm not mistaken: - '0040' should be the bank code - '0440116243' should be the bank account number

(venv)
┌─[✓]─[usuario@dellari]─[~]
└──╼ pip show schwifty
Name: schwifty
Version: 2024.1.1.post0
Summary: 
Home-page: 
Author: 
Author-email: Martin Domke <mail@martindomke.net>
License: 
Location: /home/usuario/Shuttle99/venv/lib/python3.10/site-packages
Requires: iso3166, pycountry
Required-by: 
(venv) 
┌─[✓]─[usuario@dellari]─[~]
└──╼ python3
Python 3.10.12 (main, Nov 20 2023, 15:14:05) [GCC 11.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> bank_code = '0040'
>>> account_number = '0440116243'
>>> country = 'DK'
>>> import schwifty
>>> schwifty.IBAN.generate('DK', bank_code, account_number)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/usuario/Shuttle99/venv/lib/python3.10/site-packages/schwifty/iban.py", line 111, in generate
    bban = BBAN.from_components(
  File "/home/usuario/Shuttle99/venv/lib/python3.10/site-packages/schwifty/bban.py", line 101, in from_components
    raise exceptions.InvalidAccountCode(
schwifty.exceptions.InvalidAccountCode: Account code exceeds maximum size 9
>>> 

[mdomke]

The domestic account number for Denmark seems to be 9 digits long, so that in your example it would be 044011624 the trailing 3 is actually the national check digit. There is however a problem with the current implementation of the IBAN generation in that regard.

1. The national checksum digit for Denmark is not automatically calculated (I still have to find a source for the algorithm to use)
2. It is currently not possible to provide the national check digit by hand to the IBAN.generate-method.

I will try to address both issues in the upcoming release.

[mdomke]

On the other hand it would be good to understand if the Danish bank codes in the wild are in fact 9 digits long and the check digit ist only added when calculating the BBAN.

[mdomke]

After reading through this document from the ECBS again, I think it is a legit idea to assume that the account numbers are actually provided as 10-digit long strings. It seems there is no official documentation on the actual algorithms begin used. I think I will just adapt the spec in the IBAN registry accordingly...

[mdomke]

The release 2024.04.0 does now assume that Danish account numbers are always 10-digits long.

[AriMaritano]

That's great, thanks @mdomke ! :)