ISO 3166-1 Alpha-2 Country Code Regex for Python

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching iso 3166-1 alpha-2 country 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

# ISO 3166-1 Alpha-2 Country Code
# ReDoS-safe | RegexVault — Localization > Locale & Language

import re

iso_31661_alpha2_country_code_pattern = re.compile(r'^[A-Z]{2}$')

def validate_iso_31661_alpha2_country_code(value: str) -> bool:
    return bool(iso_31661_alpha2_country_code_pattern.fullmatch(value))

# Example
print(validate_iso_31661_alpha2_country_code("US"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Localization > Locale & Language 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

ISO 3166-1 alpha-2 uses uppercase. Exceptions: UK is not a valid code (GB is used for the United Kingdom). XK is used for Kosovo informally. EU is a special supranational code. Validate against the official ISO 3166 Maintenance Agency list.