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?

Agent

Where is your regex, and what is the problem with it? – Hieratic

Answer 1

I had the same question. This is the most thorough regex pattern I could find. PEP440 links to the codebase of the packaging library in it's references section.

pip install packaging

To access just the pattern string you can use the global

from packaging import version
version.VERSION_PATTERN

See: https://github.com/pypa/packaging/blob/21.3/packaging/version.py#L225-L254

VERSION_PATTERN = r"""
    v?
    (?:
        (?:(?P<epoch>[0-9]+)!)?                           # epoch
        (?P<release>[0-9]+(?:\.[0-9]+)*)                  # release segment
        (?P<pre>                                          # pre-release
            [-_\.]?
            (?P<pre_l>(a|b|c|rc|alpha|beta|pre|preview))
            [-_\.]?
            (?P<pre_n>[0-9]+)?
        )?
        (?P<post>                                         # post release
            (?:-(?P<post_n1>[0-9]+))
            |
            (?:
                [-_\.]?
                (?P<post_l>post|rev|r)
                [-_\.]?
                (?P<post_n2>[0-9]+)?
            )
        )?
        (?P<dev>                                          # dev release
            [-_\.]?
            (?P<dev_l>dev)
            [-_\.]?
            (?P<dev_n>[0-9]+)?
        )?
    )
    (?:\+(?P<local>[a-z0-9]+(?:[-_\.][a-z0-9]+)*))?       # local version
"""

Of course this example is specific to Python's flavor of regex.

Neutretto

Thank you, this is the answer I needed. – Agent

you've included your comments in a regular string, so I don't expect this to work as-is – Digression

While this may be comprehensive I cannot use it as branch matching pattern in Travis. – Bebebebeerine

It can be used with _regex = re.compile(r"^\s*" + VERSION_PATTERN + r"\s*$", re.VERBOSE | re.IGNORECASE) – Baese

2024 version is here: github.com/pypa/packaging/blob/24.1/src/packaging/… – Lennyleno

Answer 2

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*)?

Agent

It was a difficult problem to solve, and could very well be useful to someone working with Python packaging. Does that not make it a decent question? – Agent

More to the point, if anyone has a better solution I'd really like to know. – Agent

first thing first..ask the entire question..your regex has much more information than you pointed out in the question.. – Havener

This does not match examples stated in PEP440, for example 1.0+ubuntu.1 – Lennyleno