Full Query String Regex for Python

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching full query string, 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

# Full Query String
# ReDoS-safe | RegexVault — Web & Network > URL

import re

full_query_string_pattern = re.compile(r'^\?(?:[a-zA-Z0-9_\-.~%+]+(?:=[a-zA-Z0-9_\-.~%+:@!$'()*,;/?]*)?(?:&[a-zA-Z0-9_\-.~%+]+(?:=[a-zA-Z0-9_\-.~%+:@!$'()*,;/?]*)?)*)?(?=$|#|\s)$')

def validate_full_query_string(value: str) -> bool:
    return bool(full_query_string_pattern.fullmatch(value))

# Example
print(validate_full_query_string("?key=value"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > URL 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

Bare ? (empty query string) is valid per RFC 3986. Key-only parameters without = are also valid (e.g., ?flag). Use in combination with URL host matching for full URL validation.