What3Words Address Regex for Python

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching what3words address, ported and verified for Python. Identity and credential patterns need both correctness and safety, since they're frequent targets for adversarial input. The snippet below is ready to drop into your Python project — whether you're validating in a Django view, a FastAPI endpoint, or a standalone data processing script.

Python Implementation

# What3Words Address
# ReDoS-safe | RegexVault — Identity & PII > Location PII

import re

what3words_address_pattern = re.compile(r'^[a-z]+(?:\.[a-z]+){2}$')

def validate_what3words_address(value: str) -> bool:
    return bool(what3words_address_pattern.fullmatch(value))

# Example
print(validate_what3words_address("filled.count.soap"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Identity & PII > Location PII category and carries a ReDoS-safe certification. That matters for Python developers because particularly important in Python web servers where CPU-bound regex operations can stall concurrent request handling. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

What3Words divides the world into 3m × 3m squares, each with a unique 3-word address. The API is proprietary. Format validation can check the 3-word pattern but validity of the address requires the W3W API. 57 trillion unique combinations globally.