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"""
This module is responsible for generating the check digit and formatting
SBN numbers.
"""
from typing import Any, Optional
class SBN:
MAX_LENGTH = 9
def __init__(
self,
registrant: Optional[str] = None,
publication: Optional[str] = None,
) -> None:
self.registrant = registrant
self.publication = publication
class SBN9(SBN):
def __init__(self, *args: Any, **kwargs: Any) -> None:
super().__init__(*args, **kwargs)
self.check_digit = self._check_digit()
def _check_digit(self) -> str:
"""Calculate the check digit for SBN-9.
SBNs use the same check digit calculation as ISBN. See
https://en.wikipedia.org/wiki/International_Standard_Book_Number
for calculation. Only modification is weights range from 1 to 9
instead of 1 to 10.
"""
weights = range(1, 9)
body = "".join([part for part in [self.registrant, self.publication] if part is not None])
remainder = sum(int(b) * w for b, w in zip(body, weights)) % 11
check_digit = "X" if remainder == 10 else str(remainder)
return str(check_digit)
def format(self, separator: str = "") -> str:
return separator.join(
[
part
for part in [
self.registrant,
self.publication,
self.check_digit,
]
if part is not None
]
)
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