bw-mutley/pregex

PRegEx - Programmable Regular Expressions

PRegEx - Programmable Regular Expressions

PRegEx is a Python module that can be used in order to construct Regular Expression patterns in a more human-friendly way.

Installation

You can start using PRegEx by installing it via pip:

pip install pregex

Usage

In PRegEx, everything is a Programmable Regular Expression, or "Pregex" for short. This makes it easy for simple Pregex instances to be combined into more complex ones! Within the code snippet below, we construct a Pregex instance that will match any URL that ends with either ".com" or ".org" as well as any IP address for which a 4-digit port number is specified. Furthermore, in the case that a match is a URL it's domain name will be separately captured as well.

from pregex.classes import AnyFrom, AnyDigit, AnyWhitespace
from pregex.quantifiers import Optional, Enforced
from pregex.groups import CapturingGroup
from pregex.tokens import Backslash
from pregex.operators import Either
from pregex.pre import Pregex

pre: Pregex = \
        Optional("http" + Optional('s') + "://") + \
        Optional("www.") + \
        Either(
            Enforced(AnyDigit() | AnyFrom(".")) +
            ":" + 
            4 * AnyDigit(),
            
            CapturingGroup(
                Enforced(~ (AnyWhitespace() | AnyFrom(":", Backslash())))
            ) +
            Either(".com", ".org")
        )

We can then easily fetch the resulting Pregex instance's underlying RegEx pattern.

regex = pre.get_pattern()

This is the RegEx pattern that the above method returns. Yikes!

(?:https?\:\/\/)?(?:www\.)?(?:[0-9\.]+\:[0-9]{4}|([^\r\:\n\x0c\\ \t\x0b]+)(?:\.com|\.org))

Besides from having access to its underlying pattern, we can use a Pregex instance to find matches within a string. Consider for example the following piece of text:

text = "text--192.168.1.1:8000--text--http://www.wikipedia.orghttps://youtube.com--text"

We can scan the above string for any possible matches by invoking the instance's "get_matches" method:

matches = pre.get_matches(text)

Looks like there were three matches:

['192.168.1.1:8000', 'http://www.wikipedia.org', 'https://youtube.com']

Likewise, we can invoke the instance's "get_groups" method to get any captured groups.

groups = pre.get_groups(text)

As expected, there were only two captured groups as the first match is not a URL and therefore there did not exist a domain name to capture.

[(None,), ('wikipedia',), ('youtube',)]