ISO 3166-1 Alpha-3 Country Code Regex for Python

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching iso 3166-1 alpha-3 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-3 Country Code
# ReDoS-safe | RegexVault — Localization > Locale & Language

import re

iso_31661_alpha3_country_code_pattern = re.compile(r'^[A-Z]{3}$')

def validate_iso_31661_alpha3_country_code(value: str) -> bool:
    return bool(iso_31661_alpha3_country_code_pattern.fullmatch(value))

# Example
print(validate_iso_31661_alpha3_country_code("USA"))  # 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-3 maps to alpha-2: USA=US, GBR=GB, SGP=SG, AUS=AU, CHN=CN, DEU=DE, JPN=JP. Alpha-3 is used in passports (ICAO 9303), UN statistics, and some financial systems. Same 3-letter format as ISO 4217 currency codes — context determines which.