Implements BE BBAN checksum check

schwifty/checksum/__init__.py

@@ -37,3 +37,4 @@ def register(algorithm_cls: Type[Algorithm], prefix: Optional[str] = None) -> Ty
 
 from schwifty.checksum import germany  # noqa
 from schwifty.checksum import italy  # noqa
+from schwifty.checksum import belgium  # noqa

schwifty/checksum/belgium.py

@@ -0,0 +1,18 @@
+import functools
+
+from schwifty import checksum
+
+
+register = functools.partial(checksum.register, prefix="BE")
+
+
+@register
+class DefaultAlgorithm(checksum.Algorithm):
+    name = "default"
+    accepts = checksum.InputType.BBAN
+
+    def compute(self, bban: str) -> str:
+        return str(int(bban[:-2]) % 97)
+
+    def validate(self, bban: str) -> bool:
+        return bban[-2:] == self.compute(bban)

schwifty/iban.py

@@ -43,6 +43,20 @@ def add_bban_checksum(country_code: str, bban: str) -> str:
     if country_code == "IT":
         checksum = algorithms["IT:default"].compute(bban[1:])
         bban = checksum + bban[1:]
+    elif country_code == "BE":
+        """
+        The Belgian account format is XXX-YYYYYYY-ZZ where:
+            - XXX: bank code
+            - YYYYYYY: account number
+            - ZZ: mod 97 remainder of XXYYYYYYY
+        """
+        # The BBAN as passed in does not have the checksum yet
+        bank_code, account_number = bban[:3], bban[3:]
+        # Remove extra zeroes and fill up to 7 spaces again
+        account_number = account_number.lstrip("0").zfill(7)
+        # Concatenate again, leave space for the checksum digits
+        checksum = algorithms["BE:default"].compute(f"{bank_code}{account_number}??")
+        bban = f"{bank_code}{account_number}{checksum}"
     return bban
 
 

tests/test_checksum.py

@@ -89,3 +89,11 @@ def test_german_checksum_success(account_code, algorithm_name):
 )
 def test_german_checksum_failure(account_code, algorithm_name):
     assert algorithms[algorithm_name].validate(account_code) is False
+
+
+def test_belgium_checksum():
+    assert algorithms["BE:default"].validate("539007547034") is True
+
+
+def test_belgium_checksum_failure():
+    assert algorithms["BE:default"].validate("050000123456") is False

tests/test_iban.py

@@ -1,6 +1,5 @@
 import pytest
 from pycountry import countries
-
 from schwifty import IBAN
 from schwifty.exceptions import SchwiftyException
 
@@ -152,6 +151,9 @@ def test_iban_properties():
         (("GB", "NWBK", "31926819", "601613"), "GB29NWBK60161331926819"),
         (("GB", "NWBK", "31926819"), "GB66NWBK00000031926819"),
         (("GB", "NWBK601613", "31926819"), "GB29NWBK60161331926819"),
+        (("BE", "050", "123"), "BE66050000012343"),
+        (("BE", "050", "123456"), "BE45050012345689"),
+        (("BE", "539", "0075470"), "BE68539007547034"),
     ],
 )
 def test_generate_iban(components, compact):
@@ -206,3 +208,8 @@ def test_bic_from_iban(iban, bic):
 
 def test_unknown_bic_from_iban():
     assert IBAN("SI72000001234567892").bic is None
+
+
+def test_be_generated_iban_valid():
+    iban = IBAN.generate("BE", bank_code="050", account_code="123456")
+    assert iban.validate(validate_bban=True)