Overview

docs
tests
package

The goal of reagex (from “readable regular expression”) is to suggest a way for writing complex regular expressions with many capturing groups in a readable way.

At the moment, it contains just one very simple function (called reagex) and an utility function, but any function which could be useful for writing readable patterns is welcome.

Note: Publishing this ridiculously small project is an excuse to familiarize with python packaging, DevOps tools and the entire workflow behind the publication of an open-source project. The project template was generated using https://github.com/ionelmc/cookiecutter-pylibrary/ which is obviously an overkill for a “one-function-project”.

• Free software: BSD 2-Clause License

Usage

The core function reagex is just a wrapper of str.format and it works in the same way. See the example

import re
from reagex import reagex

# A sloppy pattern for an italian address (just to show how it works)
pattern = reagex(
    '{_address}, {postcode} {city} {province}',
    # groups starting with "_" are non-capturing
    _address = reagex(
        '{street} {number}',
        street = '(via|contrada|c/da|c[.]da|piazza|p[.]za|p[.]zza) [a-zA-Z]+',
        number = 'snc|[0-9]+'
    ),
    postcode = '[0-9]{5}',
    city = '[A-Za-z]+',
    province = '[A-Z]{2}'
)

matcher = re.compile(pattern)
match = matcher.fullmatch('via Roma 123, 12345 Napoli NA')
print(match.groupdict())

# prints:
#   {'city': 'Napoli',
#    'number': '123',
#    'postcode': '12345',
#    'province': 'NA',
#    'street': 'via Roma'}

Groups starting by '_' are non-capturing. The rest are all named capturing groups.

Why not…

Why not using just re.VERBOSE?

I think reagex is easier to write and to read:

• with reagex, you first describe the structure of the pattern in terms of groups, then you provide a pattern for each group; with re.VERBOSE you have to define the groups in the exact position they must be matched: to get the high-level structure of the pattern you may need to read multiple lines at the same indentation level
• with re.VERBOSE you just write a big string; with reagex you get syntax highlighting which helps readability
• white-spaces don’t need any special treatment
• “{group_name}” is nicer than “(?P<group_name>)”

Installation

pip install reagex

Documentation

https://python-reagex.readthedocs.io/

Development

Possible improvements:

1. make some meaningful use of the format_spec in {group_name:format_spec}
2. add utility functions like repeated to help writing common patterns in a readable way

Testing

To run all the tests:

tox

Note, to combine the coverage data from all the tox environments run:

Windows	set PYTEST_ADDOPTS=--cov-append tox
Other	PYTEST_ADDOPTS=--cov-append tox