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?

Where is your regex, and what is the problem with it? – jonrsharpe Jun 22 '16 at 15:14 — jonrsharpe, Jun 22 '16 at 15:14

score 7 · Accepted Answer · answered Jun 24 '16 at 18:55

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/16.7/packaging/version.py#L159

# Deliberately not anchored to the start and end of the string, to make it
# easier for 3rd party code to reuse
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.

you've included your _comments_ in a regular string, so I don't expect this to work as-is — axolotl, Jan 26 '19 at 19:12
While this may be comprehensive I cannot use it as branch matching pattern in Travis. — sorin, Oct 25 '19 at 19:03

score 4 · Answer 2 · answered Jun 22 '16 at 15:12

4

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*)?

answered Jun 22 '16 at 15:12

Leo

779
8
19

1

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? – Leo Jun 22 '16 at 15:20
More to the point, if anyone has a better solution I'd really like to know. – Leo Jun 22 '16 at 15:21
first thing first..ask the entire question..your regex has much more information than you pointed out in the question.. – rock321987 Jun 22 '16 at 15:26

Regex to match PEP440 compliant version strings

2 Answers2

Explained