International Phone with Formatting (Liberal) Regex for Python

What this pattern does

This page provides a well-structured, multi-part regular expression for matching international phone with formatting (liberal), 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

# International Phone with Formatting (Liberal)
# ReDoS-safe | RegexVault — Localization > Phone Numbers

import re

international_phone_with_formatting_liberal_pattern = re.compile(r'^\+?[1-9][0-9]{0,2}[\s.()-]{0,2}[0-9][0-9\s.()-]{5,15}[0-9]$')

def validate_international_phone_with_formatting_liberal(value: str) -> bool:
    return bool(international_phone_with_formatting_liberal_pattern.fullmatch(value))

# Example
print(validate_international_phone_with_formatting_liberal("+1 (212) 555-0100"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Localization > Phone Numbers 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

Liberal pattern for accepting phone numbers from international forms. Strip all non-digits except leading + before storing. Normalize to E.164 for storage and comparison.