Question about function IBAN._validate_iban_checksum()

[neimad1985]

Hello :)

Quick question please.
In the code of function IBAN._validate_iban_checksum(), located at this permalink:

schwifty/schwifty/iban.py

Line 239 in 1b66427

def _validate_iban_checksum(self) -> None:

I am wondering about the if condition:

if self.numeric % 97 != 1 or not checksum_algo.validate([self.bban, self.country_code], self.checksum_digits):

Aren't the two parts self.numeric % 97 != 1 and checksum_algo.validate([self.bban, self.country_code], self.checksum_digits) doing exactly the same check ?

The only difference I see is that for the first condition, many random types of iban generation could lead to obtaining one with 1 as the remainder of modulo 97, whereas in the second condition we explicitly check that the remainder was obtained with the proper iso7064 calculation method.
Am I right ? Would it be correct to keep only the second part of the if condition and get rid of the first part ? Or am I missing something ?

Thanks

[Natim]

I remember asking myself the same question, I believe if you try to remove it and run the test you will hit the case where it is needed.

[neimad1985]

I just run the full test suite as is: all green.
Then I removed the first condition: all green.
Then I put back the first condition and remove the second one: all green.
I didn't hit the case you were guessing about.
Any other insight on this ?
Not that this is very important actually, it's just for my comprehension of the code.
I felt that the two conditions were redundant and wanted to make sure whether I was right or wrong.