cnpj-cd 1.0.1

Utility resources to calculate check digits on CNPJ (Brazilian employer ID)

Utility class to calculate check digits on CNPJ (Brazilian employer ID).

Python Support

Passing ✔	Passing ✔	Passing ✔	Passing ✔	Passing ✔

Installation

$ pip install cnpj-cd

Import

from cnpj_cd import CnpjCheckDigits

Usage

Basic Usage

# Calculate check digits from a 12-digit CNPJ base
check_digits = CnpjCheckDigits("914157320007")

print(check_digits.first_digit)    # returns 9
print(check_digits.second_digit)   # returns 3
print(check_digits.to_string())    # returns '91415732000793'
print(check_digits.to_list())      # returns [9, 1, 4, 1, 5, 7, 3, 2, 0, 0, 0, 7, 9, 3]

Input Formats

The CnpjCheckDigits class accepts multiple input formats:

String Input

# Plain string (non-numeric characters are automatically stripped)
check_digits = CnpjCheckDigits("914157320007")
check_digits = CnpjCheckDigits("91.415.732/0007")  # formatting is ignored
check_digits = CnpjCheckDigits("914157320007")      # 12 digits
check_digits = CnpjCheckDigits("91415732000793")    # 14 digits (only first 12 are used)

List of Strings

# List of single-character strings
check_digits = CnpjCheckDigits(["9", "1", "4", "1", "5", "7", "3", "2", "0", "0", "0", "7"])

# List with multi-digit strings (automatically flattened)
check_digits = CnpjCheckDigits(["914157320007"])     # flattens to individual digits
check_digits = CnpjCheckDigits(["91", "415", "732", "0007"])  # also flattens

List of Integers

# List of single-digit integers
check_digits = CnpjCheckDigits([9, 1, 4, 1, 5, 7, 3, 2, 0, 0, 0, 7])

# List with multi-digit integers (automatically flattened)
check_digits = CnpjCheckDigits([914157320007])       # flattens to individual digits
check_digits = CnpjCheckDigits([914, 157, 320, 7])  # also flattens

Properties

first_digit: int

Returns the first check digit (13th digit of the CNPJ).

check_digits = CnpjCheckDigits("914157320007")
print(check_digits.first_digit)  # returns 9

second_digit: int

Returns the second check digit (14th digit of the CNPJ).

check_digits = CnpjCheckDigits("914157320007")
print(check_digits.second_digit)  # returns 3

Methods

to_list() -> list[int]

Returns the complete CNPJ as a list of integers (12 base digits + 2 check digits).

check_digits = CnpjCheckDigits("914157320007")
print(check_digits.to_list())  # returns [9, 1, 4, 1, 5, 7, 3, 2, 0, 0, 0, 7, 9, 3]

to_string() -> str

Returns the complete CNPJ as a string (12 base digits + 2 check digits).

check_digits = CnpjCheckDigits("914157320007")
print(check_digits.to_string())  # returns '91415732000793'

Examples

from cnpj_cd import CnpjCheckDigits

# Calculate check digits for a CNPJ base
base = "914157320007"
check_digits = CnpjCheckDigits(base)

# Get individual check digits
first = check_digits.first_digit    # 9
second = check_digits.second_digit   # 3

# Get complete CNPJ
complete = check_digits.to_string()  # '91415732000793'

# Work with formatted input
formatted = CnpjCheckDigits("91.415.732/0007")
print(formatted.to_string())  # '91415732000793'

# Work with list input
list_input = CnpjCheckDigits([9, 1, 4, 1, 5, 7, 3, 2, 0, 0, 0, 7])
print(list_input.to_string())  # '91415732000793'

Error Handling

The package raises specific exceptions for different error scenarios:

CnpjTypeError

Raised when the input type is not supported (must be str, list[str], or list[int]).

from cnpj_cd import CnpjCheckDigits, CnpjTypeError

try:
    CnpjCheckDigits(12345678901234)  # int not allowed
except CnpjTypeError as e:
    print(e)  # CNPJ input must be of type str, list[str] or list[int]. Got "int".

CnpjInvalidLengthError

Raised when the input does not contain 12 to 14 digits.

from cnpj_cd import CnpjCheckDigits, CnpjInvalidLengthError

try:
    CnpjCheckDigits("12345678901")  # only 11 digits
except CnpjInvalidLengthError as e:
    print(e)  # Parameter "12345678901" does not contain 12 to 14 digits. Got 11.

CnpjCheckDigitsCalculationError

Raised when the check digit calculation fails due to invalid sequence length.

from cnpj_cd import CnpjCheckDigits, CnpjCheckDigitsCalculationError

# This is an internal error that should not occur in normal usage
# It happens when the sequence passed to _calculate() has invalid length

Features

• ✅ Multiple Input Formats: Accepts strings, lists of strings, or lists of integers
• ✅ Format Agnostic: Automatically strips non-numeric characters from string input
• ✅ Auto-Expansion: Automatically expands multi-digit numbers in lists to individual digits
• ✅ Lazy Evaluation: Check digits are calculated only when accessed (via properties)
• ✅ Type Safety: Built with Python 3.10+ type hints
• ✅ Zero Dependencies: No external dependencies required
• ✅ Comprehensive Error Handling: Specific exceptions for different error scenarios

API Reference

CnpjCheckDigits Class

Constructor

CnpjCheckDigits(cnpj_digits: str | list[str] | list[int]) -> CnpjCheckDigits

Creates a new CnpjCheckDigits instance from the provided CNPJ base digits.

Parameters:

• cnpj_digits (str | list[str] | list[int]): The CNPJ base digits (12-14 digits). Can be:
  • A string with 12-14 digits (formatting characters are ignored)
  • A list of strings (each string can be a single digit or multi-digit number)
  • A list of integers (each integer can be a single digit or multi-digit number)

Raises:

• CnpjTypeError: If the input type is not supported
• CnpjInvalidLengthError: If the input does not contain 12-14 digits

Returns:

• CnpjCheckDigits: A new instance ready to calculate check digits

Properties

first_digit: int

The first check digit (13th digit of the CNPJ). Calculated lazily on first access.

second_digit: int

The second check digit (14th digit of the CNPJ). Calculated lazily on first access.

Methods

to_list() -> list[int]

Returns the complete CNPJ as a list of 14 integers (12 base digits + 2 check digits).

to_string() -> str

Returns the complete CNPJ as a string of 14 digits (12 base digits + 2 check digits).

Calculation Algorithm

The package calculates CNPJ check digits using the official Brazilian algorithm:

1. First Check Digit (13th position):

   • Uses digits 1-12 of the CNPJ base
   • Applies weights: 5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2 (from right to left)
   • Calculates: sum(digit × weight) % 11
   • Result: 0 if remainder < 2, otherwise 11 - remainder

2. Second Check Digit (14th position):

   • Uses digits 1-12 + first check digit
   • Applies weights: 6, 5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2 (from right to left)
   • Calculates: sum(digit × weight) % 11
   • Result: 0 if remainder < 2, otherwise 11 - remainder

Dependencies

• Python: >= 3.10

No external dependencies required.

Contribution & Support

We welcome contributions! Please see our Contributing Guidelines for details. But if you find this project helpful, please consider:

• ⭐ Starring the repository
• 🤝 Contributing to the codebase
• 💡 Suggesting new features
• 🐛 Reporting bugs

License

This project is licensed under the MIT License - see the LICENSE file for details.

Changelog

See CHANGELOG for a list of changes and version history.

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