def calculate(data: str) -> str:
"""Calculates ISBN Check Digits.
Args:
data: A string of characters representing an ISBN code without the check digit
Returns:
str: The check digit that was missing
Examples:
>>> from checkdigit import isbn
>>> # ISBN-10
>>> isbn.calculate("043942089")
'X'
>>> # ISBN-13
>>> isbn.calculate("978-1-86197-876")
'9'
"""
data = cleanse(data)
if len(data) == 9:
# ISBN 10 (without the check digit)
# Multiply first digit by 10, second by 9, ... and take the sum
total_sum = sum(
int(digit) * weight for digit, weight in zip(data, range(10, 0, -1))
)
return convert(11 - (total_sum % 11))
# elif not required since return above (and makes pylint happy)
if len(data) == 12:
# ISBN weights is 1 for odd positions and 3 for even
# Since there are 12 digits, multiply weights by 6
weights = (1, 3) * 6
# Multiply each digit by its weight
total_sum = sum(int(digit) * weight for digit, weight in zip(data, weights))
# Return final check digit and type of barcode
return convert(10 - (total_sum % 10))
return "Invalid"
def calculate10(data: str) -> str:
"""Calculates ISBN-10 Check Digit.
Args:
data: A string of 9 characters
Returns:
str: The check digit that was missing
"""
data = cleanse(data)
# Multiply first digit by 10, second by 9, ... and take the sum
total_sum = sum(
int(digit) * weight for digit, weight in zip(data, range(10, 0, -1))
)
return convert(11 - (total_sum % 11))
def calculate10(data: str) -> str:
"""Calculates ISBN-10 Check Digit.
Args:
data: A string of 9 characters
Returns:
str: The check digit that was missing
"""
data = cleanse(data)
total_sum = 0
multiply_counter = 10
for item in data:
total_sum += int(item) * multiply_counter
multiply_counter -= 1 # Multiplies first digit by 10, second by 9...
check_digit = 11 - (total_sum % 11)
return convert(check_digit)
def calculate13(data: str, barcode: str = "isbn") -> str:
"""Calculates ISBN-13 Check Digit.
Args:
data: A string of 12 characters
barcode: The type of code (either isbn or upc)
Returns:
str: The check digit that was missing
"""
data = cleanse(data)
# ISBN weights is 1 for odd positions and 3 for even
# The opposite is true for upc
weights = (1, 3) * 6 if barcode == "isbn" else (3, 1) * 6
# Multiply each digit by its weight
total_sum = sum(int(digit) * weight for digit, weight in zip(data, weights))
# Return final check digit and type of barcode
return convert(10 - (total_sum % 10), barcode)
def missing(data: str) -> str:
"""Calculates a missing digit in a GS1 Code.
This method works for all fixed length numeric GS1 data structures
(including GDTI, GLN, GRAI, etc.) that require a check digit.
Args:
data: A string of characters representing a full ISBN code
with a question mark representing a missing character
Returns:
str: The missing value that should've been where the question mark was
"""
data = cleanse(data)
for poss_digit in range(10): # Brute Force the 10 options
option = convert(poss_digit)
# tests it with the generated number
# If this fails, the next number is tried
if validate(data.replace("?", option)):
return option
return "Invalid"
def missing(data: str) -> str:
"""Calculates a missing digit in an ISBN Code.
Args:
data: A string of characters representing a full ISBN code
with a question mark representing a missing character
Returns:
str: The missing value that should've been where the question mark was
"""
data = cleanse(data)
for poss_digit in range(11): # Brute Force the 11 options
option = convert(poss_digit)
# Depending on the size of the data, the relevant validating function
# tests it with the generated number
# If this fails, the next number is tried
if (len(data) == 10 and validate10(data.replace("?", option))) or (
len(data) == 13 and validate13(data.replace("?", option))
):
return option
return "Invalid"
def calculate(data: str) -> str:
"""Calculates GS1 Check Digit.
This method works for all fixed length numeric GS1 data structures
(including GDTI, GLN, GRAI, etc.) that require a check digit.
Args:
data: A string of characters
Returns:
str: The check digit that was missing
"""
data = cleanse(data)
data = data[::-1] # Reverse the barcode, as last digit is always multiplied by 3
total_sum = 0
for index, value in enumerate(data):
if index % 2 == 0:
total_sum += int(value) * 3
else:
total_sum += int(value)
next_multiple_of_ten = int(math.ceil(total_sum / 10.0)) * 10
check_digit = next_multiple_of_ten - total_sum
return convert(check_digit, "gs1")
def calculate13(data: str, barcode: str = "isbn") -> str:
"""Calculates ISBN-13 Check Digit.
Args:
data: A string of 12 characters
barcode: The type of code (either isbn or upc)
Returns:
str: The check digit that was missing
"""
data = cleanse(data)
mod_number = 0 if barcode == "isbn" else 1
total_sum = 0
position_counter = 1 # 1 based indexing for data
for item in data:
digit = int(item)
if position_counter % 2 == mod_number:
total_sum += digit * 3 # Multiplies by 3 if position is even
else:
total_sum += digit
position_counter += 1
final_value = 10 - (total_sum % 10)
return convert(final_value, barcode)