def calculate(data: str) -> str:
"""Calculates the luhn check digit
Args:
data: A block of data without the check digit
Returns:
str: A string representing the missing check digit
"""
data = cleanse(data)
position_counter = 1 # 1-based indexing
total_sum = 0
for item in data[::-1]: # Reverses String
digit = int(item)
if position_counter % 2: # If position number is odd with reversed string
add_value = digit * 2
if add_value > 9:
for number in str(
add_value): # Adds individual digits together
total_sum += int(number)
else:
total_sum += add_value
else:
total_sum += digit
position_counter += 1
return convert(10 - (total_sum % 10), "luhn")
def validate13(data: str) -> bool:
"""Validates ISBN-13
Args:
data: A string of characters representing a full ISBN-13 code
Returns:
bool: A boolean representing whether the check digit validates the data
"""
data = cleanse(data)
return calculate13(data[:-1]) == data[-1]
def validate(data: str) -> bool:
"""Validates a luhn check digit
Args:
data: A string of characters representing a full luhn code
Returns:
bool: A boolean representing whether the check digit validates the data or not
"""
data = cleanse(data)
return (
calculate(data[:-1]) == data[-1]
) # Determines if calculated Check Digit of the data is the last digit given
def calculate(data: str, even: bool = True) -> str:
"""Adds a parity bit onto the end of a block of data
Args:
data: A string containing binary digits
even: Whether to use even parity (otherwise uses odd parity)
Returns:
str: The original data with the parity bit added to the end
"""
data = cleanse(data)
if (even and not data.count("1") % 2) or (not even
and data.count("1") % 2):
return data + "0"
return data + "1"
def missing(data: str) -> str:
"""Calculates a missing digit in a luhn code
Args:
data: A string of characters representing a full luhn code with a question mark for 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
if validate(data.replace("?", str(poss_digit))):
return str(poss_digit)
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)
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 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 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)