npm Version Range (Caret ^) Regex for Python

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching npm version range (caret ^), 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

# npm Version Range (Caret ^)
# ReDoS-safe | RegexVault — Dev & Systems > SemVer

import re

npm_version_range_caret_pattern = re.compile(r'^\^(0|[1-9][0-9]*)\.(0|[1-9][0-9]*|x|\*)\.(0|[1-9][0-9]*|x|\*)(?:-((?:0|[1-9][0-9]*|[0-9]*[a-zA-Z\-][a-zA-Z0-9\-]*)(?:\.(?:0|[1-9][0-9]*|[0-9]*[a-zA-Z\-][a-zA-Z0-9\-]*))*))?$')

def validate_npm_version_range_caret(value: str) -> bool:
    return bool(npm_version_range_caret_pattern.fullmatch(value))

# Example
print(validate_npm_version_range_caret("^1.2.3"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Dev & Systems > SemVer 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

^1.2.3 allows >=1.2.3 <2.0.0. ^0.2.3 allows >=0.2.3 <0.3.0. ^0.0.3 allows >=0.0.3 <0.0.4. This reflects npm's caret range semantics.