Regex to match PEP440 compliant version strings

Question

PEP 440 lays out what is the accepted format for version strings of Python packages.

These can be simple, like: 0.0.1

Or complicated, like: 2016!1.0-alpha1.dev2

What is a suitable regex which could be used for finding and validating such strings?

Answer 1

I think this should comply with PEP440:

^(\d+!)?(\d+)(\.\d+)+([\.\-\_])?((a(lpha)?|b(eta)?|c|r(c|ev)?|pre(view)?)\d*)?(\.?(post|dev)\d*)?$

Explained

Epoch, e.g. 2016!:

(\d+!)?

Version parts (major, minor, patch, etc.):

(\d+)(\.\d+)+

Acceptable separators (., - or _):

([\.\-\_])?

Possible pre-release flags (and their normalisations; as well as post release flags r or rev), may have one or more digits following:

((a(lpha)?|b(eta)?|c|r(c|ev)?|pre(view)?)\d*)?

Post-release flags, and one or more digits:

(\.?(post|dev)\d*)?