ISBN: Fixed linting

pydantic_extra_types/isbn.py

@@ -1,5 +1,5 @@
 """
-The `pydantic_extra_types.isbn` module provides functionality to recieve and validate ISBN 
+The `pydantic_extra_types.isbn` module provides functionality to recieve and validate ISBN
 (International Standard Book Number) in 10-digit and 13-digit formats. The output is always ISBN-13.
 """
 
@@ -14,19 +14,21 @@
 def isbn10_digit_calc(isbn: str) -> str:
     total = sum(int(digit) * (10 - idx) for idx, digit in enumerate(isbn[:9]))
 
-    for check_digit in range(1,11):
+    for check_digit in range(1, 11):
         if (total + check_digit) % 11 == 0:
             valid_check_digit = 'X' if check_digit == 10 else str(check_digit)
 
     return valid_check_digit
 
+
 def isbn13_digit_calc(isbn: str) -> str:
     total = sum(int(digit) * (1 if idx % 2 == 0 else 3) for idx, digit in enumerate(isbn[:12]))
 
     check_digit = (10 - (total % 10)) % 10
 
     return str(check_digit)
 
+
 class ISBN(str):
     """Represents a ISBN and provides methods for conversion, validation, and serialization.
 
@@ -74,17 +76,12 @@ def validate_isbn_format(value: str) -> None:
         isbn_length = len(value)
 
         if isbn_length not in (10, 13):
-            raise PydanticCustomError(
-                'isbn_length',
-                f'Length for ISBN must be 10 or 13 digits, not {isbn_length}'
-            )
+            raise PydanticCustomError('isbn_length', f'Length for ISBN must be 10 or 13 digits, not {isbn_length}')
 
         if isbn_length == 10:
 
             if not value[:-1].isdigit() or ((value[-1] != 'X') and (not value[-1].isdigit())):
-                raise PydanticCustomError(
-                    'isbn10_invalid_characters', 'First 9 digits of ISBN-10 must be integers'
-                )
+                raise PydanticCustomError('isbn10_invalid_characters', 'First 9 digits of ISBN-10 must be integers')
 
         if isbn_length == 13:
             if not value.isdigit():
@@ -94,8 +91,7 @@ def validate_isbn_format(value: str) -> None:
             if value[:3] not in ('978', '979'):
                 raise PydanticCustomError(
                     'isbn_invalid_early_characters', 'The first 3 digits of ISBN-13 must be 978 or 979'
-            )
-
+                )
 
     @staticmethod
     def validate_isbn_digits(value: str) -> None:
@@ -109,13 +105,16 @@ def validate_isbn_digits(value: str) -> None:
             PydanticCustomError: If the check digit is not valid.
         """
 
+        isbn_length = len(value)
+
+        if isbn_length not in (10, 13):
+            raise PydanticCustomError('isbn_length', f'Length for ISBN must be 10 or 13 digits, not {isbn_length}')
+
         validation_functions = {10: isbn10_digit_calc, 13: isbn13_digit_calc}
-        validate = validation_functions.get(len(value))
+        validate = validation_functions.get(isbn_length)
 
         if validate(value) != value[-1]:
-            raise PydanticCustomError(
-                'isbn_invalid_digit_check_isbn', 'Provided digit is invalid for given ISBN'
-            )
+            raise PydanticCustomError('isbn_invalid_digit_check_isbn', 'Provided digit is invalid for given ISBN')
 
     @staticmethod
     def convert_isbn10_to_isbn13(value: str) -> str:
@@ -132,6 +131,6 @@ def convert_isbn10_to_isbn13(value: str) -> str:
         if len(value) == 10:
             base_isbn = '978' + value[:-1]
             isbn13_digit = isbn13_digit_calc(base_isbn)
-            return f'{base_isbn}{isbn13_digit}'
+            return ISBN(f'{base_isbn}{isbn13_digit}')
 
-        return value
+        return ISBN(value)

tests/test_isbn.py

@@ -14,8 +14,8 @@ class Book(BaseModel):
     ('8537809667', '9788537809662', True),  # ISBN-10 as input
     ('9788537809662', '9788537809662', True),  # ISBN-13 as input
     ('080442957X', '9780804429573', True),  # ISBN-10 ending in "X" as input
-    ('9788584390670', '9788584390670', True), #ISBN-13 Starting with 978
-    ('9790306406156', '9790306406156', True), # ISBN-13 starting with 979
+    ('9788584390670', '9788584390670', True),  # ISBN-13 Starting with 978
+    ('9790306406156', '9790306406156', True),  # ISBN-13 starting with 979
     # Invalid ISBNs
     ('97885843906701', None, False),  # Length: 14 (Higher)
     ('978858439067', None, False),  # Length: 12 (In Between)
@@ -47,7 +47,7 @@ def test_isbn_length(input_isbn: Any, output_isbn: str, valid: bool):
     ('853780@667', None, False),  # Non Integer in [6] position
     ('8537809@67', None, False),  # Non Integer in [7] position
     ('85378096@7', None, False),  # Non Integer in [8] position
-    ('853780966@', None, False)  # Non Integer or X in [9] position
+    ('853780966@', None, False),  # Non Integer or X in [9] position
 ]
 
 
@@ -64,8 +64,8 @@ def test_isbn10_digits(input_isbn: Any, output_isbn: str, valid: bool):
     # Valid ISBNs
     ('9788537809662', '9788537809662', True),  # ISBN-13 as input
     ('9780306406157', '9780306406157', True),  # ISBN-13 as input
-    ('9788584390670', '9788584390670', True), # ISBN-13 Starting with 978
-    ('9790306406156', '9790306406156', True), # ISBN-13 starting with 979
+    ('9788584390670', '9788584390670', True),  # ISBN-13 Starting with 978
+    ('9790306406156', '9790306406156', True),  # ISBN-13 starting with 979
 
     # Invalid ISBNs
     ('@788537809662', None, False),  # Non Integer in [0] position
@@ -95,8 +95,8 @@ def test_isbn13_digits(input_isbn: Any, output_isbn: str, valid: bool):
 isbn13_early_digits_test_cases = [
     # Valid ISBNs
     ('9780306406157', '9780306406157', True),  # ISBN-13 as input
-    ('9788584390670', '9788584390670', True), # ISBN-13 Starting with 978
-    ('9790306406156', '9790306406156', True), # ISBN-13 starting with 979
+    ('9788584390670', '9788584390670', True),  # ISBN-13 Starting with 978
+    ('9790306406156', '9790306406156', True),  # ISBN-13 starting with 979
 
     # Invalid ISBNs
     ('1788584390670', None, False),  # Does not start with 978 or 979
@@ -119,15 +119,15 @@ def test_isbn13_early_digits(input_isbn: Any, output_isbn: str, valid: bool):
     ('8537809667', '9788537809662', True),  # ISBN-10 as input
     ('9788537809662', '9788537809662', True),  # ISBN-13 as input
     ('080442957X', '9780804429573', True),  # ISBN-10 ending in "X" as input
-    ('9788584390670', '9788584390670', True), # ISBN-13 Starting with 978
-    ('9790306406156', '9790306406156', True), # ISBN-13 starting with 979
+    ('9788584390670', '9788584390670', True),  # ISBN-13 Starting with 978
+    ('9790306406156', '9790306406156', True),  # ISBN-13 starting with 979
 
     # Invalid ISBNs
     ('8537809663', None, False),  # ISBN-10 as input with wrong last digit
     ('9788537809661', None, False),  # ISBN-13 as input with wrong last digit
     ('080442953X', None, False),  # ISBN-10 ending in "X" as input with wrong last digit
-    ('9788584390671', None, False), #ISBN-13 Starting with 978 with wrong last digit
-    ('9790306406155', None, False), # ISBN-13 starting with 979 with wrong last digit
+    ('9788584390671', None, False),  # ISBN-13 Starting with 978 with wrong last digit
+    ('9790306406155', None, False),  # ISBN-13 starting with 979 with wrong last digit
 ]
 
 
@@ -144,7 +144,7 @@ def test_isbn_last_digit(input_isbn: Any, output_isbn: str, valid: bool):
     ('8537809667', '9788537809662'), 
     ('080442957X', '9780804429573'), 
     ('9788584390670', '9788584390670'),
-    ('9790306406156', '9790306406156')
+    ('9790306406156', '9790306406156'),
 ]