Canadian Postal Code Regex for Python

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching canadian postal code, ported and verified for Python. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. 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

# Canadian Postal Code
# ReDoS-safe | RegexVault — Localization > Postal Codes

import re

canadian_postal_code_pattern = re.compile(r'^([ABCEGHJKLMNPRSTVXY][0-9][ABCEGHJKLMNPRSTVWXYZ])\s?([0-9][ABCEGHJKLMNPRSTVWXYZ][0-9])$')

def validate_canadian_postal_code(value: str) -> bool:
    return bool(canadian_postal_code_pattern.fullmatch(value))

# Example
print(validate_canadian_postal_code("K1A 0B1"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Localization > Postal Codes 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

First letter identifies the province. Invalid first letters: D, F, I, O, Q, U, W (excluded because they resemble digits in some fonts or were reserved). The letter D and I are also excluded from all positions for readability.