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Accept uppercase X as the ISBN-10 check digit #32

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Accept uppercase X as the ISBN-10 check digit #32

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3 changes: 2 additions & 1 deletion string_utils/validation.py
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Original file line number Diff line number Diff line change
Expand Up @@ -68,7 +68,8 @@ def is_isbn_10(self) -> bool:

try:
for index, digit in enumerate(self.input_string):
product += int(digit) * (index + 1)
value = 10 if index == 9 and digit == 'X' else int(digit)
product += value * (index + 1)

return product % 11 == 0

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16 changes: 15 additions & 1 deletion tests/test_is_isbn_10.py
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
from unittest import TestCase

from string_utils.errors import InvalidInputError
from string_utils.validation import is_isbn_10
from string_utils.validation import is_isbn, is_isbn_10


class IsISBN10TestCase(TestCase):
Expand All @@ -26,6 +26,20 @@ def test_returns_true_for_valid_isbn_10(self):
self.assertTrue(is_isbn_10('0718079183'))
self.assertTrue(is_isbn_10('8830102180'))

def test_x_check_digit(self):
for isbn in ('080442957X', '0-8044-2957-X', '097522980X'):
with self.subTest(isbn=isbn):
self.assertTrue(is_isbn_10(isbn))
self.assertTrue(is_isbn(isbn))
self.assertTrue(is_isbn_10('080442957X', normalize=False))
self.assertFalse(is_isbn_10('0-8044-2957-X', normalize=False))

def test_invalid_x_check_digit(self):
for isbn in ('080442958X', 'X804429570', '08044295XX', '080442957x'):
with self.subTest(isbn=isbn):
self.assertFalse(is_isbn_10(isbn))
self.assertFalse(is_isbn(isbn))

def test_dashes_are_not_considered_by_default(self):
# isbn numbers have been taken from actual books on amazon
self.assertTrue(is_isbn_10('150-6715214'))
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