🇱🇰 Sri Lanka NIC Decoder

Decode Sri Lankan National Identity Card (NIC) numbers into birth date, gender, and NIC type.

This package provides a simple and accurate way to decode both:

• Old NIC format (10 characters → YYDDDxxxxV)
• New NIC format (12 digits → YYYYDDDxxxx)

The decoder uses Python's datetime module to correctly compute dates, including leap years and month boundaries.
It also implements the correct NIC day-number offset discovered from real NIC examples.

✨ Features

✔ Supports Old and New Sri Lankan NIC formats
✔ Extracts full Date of Birth
✔ Determines Gender (Male / Female)
✔ Automatically identifies NIC type
✔ Correct leap-year handling
✔ Configurable NIC day-code offset (default = 2)
✔ Clean, reusable functions
✔ Includes a structured NICInfo dataclass

📦 Installation

pip install lka-nic-decoder

🔧 Usage Example

from lka_nic_decoder import decode_nic

# Decode an old NIC
info = decode_nic("912680444V")

print(info.nic_type)      # Old NIC
print(info.gender)        # Male
print(info.birth_year)    # 1991
print(info.birth_date)    # 1991-09-24

# Decode a new NIC
info_new = decode_nic("199253600001")

print(info_new.nic_type)      # New NIC
print(info_new.gender)        # Female
print(info_new.birth_year)    # 1992
print(info_new.birth_date)    # 1992-02-05

📋 Import Methods

1. Import Specific Function (Recommended)

from lka_nic_decoder import decode_nic
info = decode_nic("912680444V")

2. Import Entire Module

import lka_nic_decoder
info = lka_nic_decoder.decode_nic("912680444V")

3. Import Multiple Functions

from lka_nic_decoder import decode_nic, parse_nic_base, nic_to_date
info = decode_nic("912680444V")
nic_type, year, day_code = parse_nic_base("912680444V")

4. Import with Alias

from lka_nic_decoder import decode_nic as decode
info = decode("912680444V")

5. Import Validation Function

from lka_nic_decoder import is_valid_nic, decode_nic

if is_valid_nic("912680444V"):
    info = decode_nic("912680444V")
    print(f"Valid NIC: {info.birth_date}")

6. Import Dataclass for Type Hints

from lka_nic_decoder import NICInfo, decode_nic

def process_nic(nic: str) -> NICInfo:
    return decode_nic(nic)

7. Import Constants

from lka_nic_decoder import DEFAULT_NIC_DAY_OFFSET, nic_to_date
custom_date = nic_to_date(1991, 268, offset=DEFAULT_NIC_DAY_OFFSET)

8. Error Handling Pattern

from lka_nic_decoder import decode_nic, is_valid_nic

try:
    if is_valid_nic("912680444V"):
        info = decode_nic("912680444V")
        print(f"Birth Date: {info.birth_date}")
except ValueError as e:
    print(f"Error: {e}")

📘 What the Decoder Extracts

Field	Example Value	Description
NIC Type	Old NIC,New NIC	Old (10 chars) or New (12 chars)
Birth Year	1991	Parsed from NIC digits
Gender	Male,Female	Based on day code (>500 → Female)
Birth Date	1991-09-24	Fully computed using datetime
Raw Day Code	268	Original 3-digit day component
Day Code	268 / -500	Adjusted for females

🧠 How NIC Decoding Works

1. NIC Type

• Old NIC (10 chars)

• Year = 1900/2000 + YY

• Day-of-year = DDD

• New NIC (12 digits)

• Year = YYYY

• Day-of-year = DDD

2. Gender

• If day code > 500 → Female
• Else → Male
• Female NICs subtract 500 from day code

3. Date Calculation

The NIC system has a known offset of +2 days, so decoding uses:

Date calculation uses:

from datetime import datetime, timedelta

start_of_year = datetime(year, 1, 1)
birth_date = start_of_year + timedelta(days=actual_day_of_year)

This ensures:

• Leap years handled properly
• Month boundaries handled
• No manual month/day mapping needed

📚 Full API Documentation

decode_nic(nic: str, offset: int = 2) -> NICInfo

Main high-level function — decodes a Sri Lankan NIC and returns a NICInfo dataclass.

Parameters:

• nic (str): The NIC number to decode (10-character old NIC or 12-digit new NIC).
• offset (int, optional): Day-of-year offset. Default is 2.

Returns:

• NICInfo object containing:
  • nic_type (str): "Old NIC" or "New NIC"
  • gender (str): "Male" or "Female"
  • birth_year (int): Year of birth
  • raw_day_code (int): Original 3-digit day code from NIC
  • day_code (int): Adjusted day code (after gender correction)
  • birth_date (date): Full date of birth as datetime.date

Example:

from lka_nic_decoder import decode_nic

info = decode_nic("912680444V")
print(info.birth_date)  # 1991-09-24

### `parse_nic_base(nic: str) -> tuple`
Parses NIC type, birth year, and raw day code without computing the full date.

**Returns:**
```python
(nic_type, birth_year, raw_day_code)

from lka_nic_decoder import parse_nic_base

nic_type, birth_year, day_code = parse_nic_base("912680444V")
print(nic_type)    # Old NIC
print(birth_year)  # 1991
print(day_code)    # 268

nic_to_date(birth_year: int, day_code: int, offset: int = 2) -> date

Converts the day-of-year code to an actual datetime.date.

Parameters:

• birth_year (int): Year of birth
• day_code (int): Adjusted day-of-year code
• offset (int, optional): NIC system day offset (default 2)

Example:

from lka_nic_decoder import nic_to_date
from datetime import date

birth_date = nic_to_date(1991, 268)
print(birth_date)  # 1991-09-24

is_valid_nic(nic: str) -> bool

Checks if a NIC string is a valid format (10-character old NIC or 12-digit new NIC).

Example:

from lka_nic_decoder import is_valid_nic

print(is_valid_nic("912680444V"))  # True
print(is_valid_nic("1234567890"))  # True
print(is_valid_nic("ABCDE"))       # False

NICInfo Dataclass

Stores all decoded NIC information in a structured object.

from dataclasses import dataclass
from datetime import date

@dataclass(frozen=True)
class NICInfo:
    nic_type: str
    gender: str
    birth_year: int
    raw_day_code: int
    day_code: int
    birth_date: date


from lka_nic_decoder import decode_nic

info = decode_nic("912680444V")
print(info.nic_type)      # Old NIC
print(info.gender)        # Male
print(info.birth_year)    # 1991
print(info.birth_date)    # 1991-09-24

🏷️ Versioning

Follows Semantic Versioning (SemVer):

1.0.18

📄 License

MIT License — permits both personal and commercial use.

🤝 Contributing

Pull requests welcome!
Open issues for improvements, validation rules, or new features.