Add DE Leitweg-ID

stdnum/de/leitweg.py

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+# leitweg.py - functions for handling Leitweg-ID
+# coding: utf-8
+#
+# Copyright (C) 2025 Holvi Payment Services Oy
+#
+# 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
+
+"""Leitweg-ID, a buyer reference or routing identifier for electronic invoices.
+
+For the successful transmission of an electronic invoice as invoicing party or
+sender, a unique identification and addressing of the invoice recipient is
+required. The Leitweg-ID must be transmitted as a mandatory requirement for
+electronic invoicing to public contracting authorities in the federal
+administration.
+
+More information:
+
+* https://leitweg-id.de/
+* https://de.wikipedia.org/wiki/Leitweg-ID
+* https://xeinkauf.de/app/uploads/2022/11/Leitweg-ID-Formatspezifikation-v2-0-2-1.pdf
+
+>>> validate('991-03730-19')
+'991-03730-19'
+>>> validate('1-03730-19')
+Traceback (most recent call last):
+    ...
+InvalidFormat: ...
+"""
+
+from __future__ import annotations
+
+import re
+
+from stdnum.exceptions import *
+
+
+pattern = re.compile(r'[0-9]{2,12}(-[0-9A-Z]{,30})?-[0-9]{2}')
+
+
+def compact(number: str) -> str:
+    """
+    Convert the number to the minimal representation. This strips the
+    number of any valid separators and removes surrounding whitespace.
+    """
+    return number.strip().upper()  # no valid separators, dashes part of the format
+
+
+def validate(number: str) -> str:
+    """
+    Check if the number provided is valid. This checks the format, state or
+    federal government code, and check digits.
+    """
+    if not isinstance(number, str):
+        raise InvalidFormat()
+
+    number = compact(number)
+
+    # 2.1 Bestandteile der Leitweg-ID
+    if not 5 <= len(number) <= 46:
+        raise InvalidLength()
+
+    # 2.1 Bestandteile der Leitweg-ID
+    if not re.fullmatch(pattern, number):
+        raise InvalidFormat()
+
+    # 2.2.1 Kennzahl des Bundeslandes/des Bundes
+    if not number[:2] in {
+        '01', '02', '03', '04', '05', '06', '07', '08', '09', '10',
+        '11', '12', '13', '14', '15', '16', '99',
+    }:
+        raise InvalidComponent()
+
+    # 2.4 Prüfziffer
+    indices = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'
+    if int(''.join(str(indices.index(c)) for c in number if c != '-')) % 97 != 1:
+        raise InvalidChecksum()
+
+    return number
+
+
+def is_valid(number: str) -> bool:
+    """Check if the number provided is valid. This checks the length and
+    check digit."""
+    try:
+        return bool(validate(number))
+    except ValidationError:
+        return False

tests/test_de_leitweg.doctest

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+test_de_leitweg.doctest - more detailed doctests for the stdnum.de.leitweg module
+
+Copyright (C) 2025 Holvi Payment Services Oy
+
+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
+
+
+This file contains more detailed doctests for the stdnum.de.leitweg module. It
+tries to validate a number of numbers that have been found online.
+
+>>> from stdnum.de import leitweg
+>>> from stdnum.exceptions import *
+
+
+These are present in the verzeichnis.leitweg-id.de directory and should all be valid numbers.
+
+>>> valid_numbers = '''
+...
+... 16066069-0001-38
+... 13-L75810002000-60
+... 057660004004-31001-55
+... 991-03730-19
+... 992-90009-96
+... 08315033-ESCHBACH6626-66
+... 09274154-NFH-05
+... 05370032-WDF5271-06
+... 09778137-ETTRINGEN868331262-55
+... 08325024-787394066-26
+... 15088205-LEUNA6877-16
+... 09471131-GDEFD96158-46
+... 09780119-RATHAUSDIETMANNSRIED7247-90
+... 09176111-ADELSCHLAG-11
+... 09274193-WHM-62
+... 09177127-GEMEINDELENGDORF-24
+... 09176122-EGWEIL-38
+... 06533010-L357921748-84
+... 09176149-NASSENFELS-39
+... 09177131-NEUCHING-08
+...
+... '''
+>>> [x for x in valid_numbers.splitlines() if x and not leitweg.is_valid(x)]
+[]
+
+
+Unknown Kennzahl des Bundes(landes).
+
+>>> leitweg.validate('55-55-20')
+Traceback (most recent call last):
+    ...
+InvalidComponent: ...
+
+
+Invalid checksum.
+
+>>> leitweg.validate('992-90009-97')
+Traceback (most recent call last):
+    ...
+InvalidChecksum: ...