Python Package Version (PEP 440) Regex for JavaScript

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching python package version (pep 440), ported and verified for JavaScript. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your JavaScript project — whether you're validating in an Express middleware, a Next.js API route, or a client-side form.

Javascript Implementation

// Python Package Version (PEP 440)
// ReDoS-safe | RegexVault — Dev & Systems > SemVer

const pythonPackageVersionPep440Regex = /^(?:([0-9]+)!)?([0-9]+(?:\.[0-9]+)*)(?:[-_.]?(?:a|alpha|b|beta|c|rc|preview)[-_.]?([0-9]+))?(?:[-_.]?post[-_.]?([0-9]+))?(?:[-_.]?dev[-_.]?([0-9]+))?(?:\+([a-zA-Z0-9]+(?:[-_.][a-zA-Z0-9]+)*))?$/i;

function validatePythonPackageVersionPep440(input: string): boolean {
  return pythonPackageVersionPep440Regex.test(input);
}

// Example
console.log(validatePythonPackageVersionPep440("1.0")); // 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 JavaScript developers because especially critical in long-running Node.js event loops where a ReDoS vulnerability can block the entire process. 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

PEP 440 allows epoch (1!), pre-release suffixes (a/alpha/b/beta/rc), post-releases (.post1), dev releases (.dev1), and local version labels (+local). Use packaging.version.Version() in Python for canonical parsing.