Contents

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

Installation

At the command line:

pip install reagex

Reference

reagex

reagex.reagex(pattern, **group_patterns)

Utility function for writing regular expressions with many capturing groups in a readable, clean and hierarchical way. It is just a wrapper of str.format and it works in the same way. A minimal example:

pattern = reagex(
    '{name} "{nickname}" {surname}',
    name='[A-Z][a-z]+',
    nickname='[a-z]+',
    surname='[A-Z][a-z]+'
)

Parameters:

• pattern (str) – a pattern where you can use str.format syntax for groups {group_name}. Groups are capturing unless they starts with '_'. For each group in this argument, this function expects a keyword argument with the same name containing the pattern for the group.
• **group_patterns (str) – patterns associated to groups; for each group in pattern of the kind {group_name} this function expects a keyword argument.

Returns:

a pattern you can pass to re functions

reagex.repeated(pattern, sep, least=1, most=None)

Returns a pattern that matches a sequence of strings that match pattern separated by strings that match sep.

For example, for matching a sequence of '{key}={value}' pairs separated by '&', where key and value contains only lowercase letters:

repeated('[a-z]+=[a-z]+', '&') == '[a-z]+=[a-z]+(?:&[a-z]+=[a-z]+)*'

Parameters:

• pattern (str) – a pattern
• sep (str) – a pattern for the separator (usually just a character/string)
• least (int, positive) – minimum number of strings matching pattern; must be positive
• most (Optional[int]) – maximum number of strings matching pattern; must be greater or equal to least

Returns:

a pattern

Contributing

Contributions are welcome, and they are greatly appreciated! Every little bit helps, and credit will always be given.

Bug reports

When reporting a bug please include:

• Your operating system name and version.
• Any details about your local setup that might be helpful in troubleshooting.
• Detailed steps to reproduce the bug.

Documentation improvements

reagex could always use more documentation, whether as part of the official reagex docs, in docstrings, or even on the web in blog posts, articles, and such.

Feature requests and feedback

The best way to send feedback is to file an issue at https://github.com/janluke/python-reagex/issues.

If you are proposing a feature:

• Explain in detail how it would work.
• Keep the scope as narrow as possible, to make it easier to implement.
• Remember that this is a volunteer-driven project, and that code contributions are welcome :)

Development

To set up python-reagex for local development:

1. Fork python-reagex (look for the “Fork” button).

2. Clone your fork locally:

   git clone git@github.com:your_name_here/python-reagex.git
   

3. Create a branch for local development:

   git checkout -b name-of-your-bugfix-or-feature
   

   Now you can make your changes locally.

4. When you’re done making changes, run all the checks, doc builder and spell checker with tox one command:

   tox
   

5. Commit your changes and push your branch to GitHub:

   git add .
   git commit -m "Your detailed description of your changes."
   git push origin name-of-your-bugfix-or-feature
   

6. Submit a pull request through the GitHub website.

Pull Request Guidelines

If you need some code review or feedback while you’re developing the code just make the pull request.

For merging, you should:

1. Include passing tests (run tox) [1].
2. Update documentation when there’s new API, functionality etc.
3. Add a note to CHANGELOG.rst about the changes.
4. Add yourself to AUTHORS.rst.

[1]	If you don’t have all the necessary python versions available locally you can rely on Travis - it will run the tests for each change you add in the pull request. It will be slower though …

Tips

To run a subset of tests:

tox -e envname -- pytest -k test_myfeature

To run all the test environments in parallel (you need to pip install detox):

detox

Authors

• Gianluca Gippetto

Changelog

0.1.2 (2018-12-16)

• Fix little mistake in the example (which is showed in PyPI, so a release was necessary to update the PyPI page).

0.1.1 (2018-12-12)

• Minor fixes and modifications to documentation

0.1.0 (2018-12-08)

• First release on PyPI.

Indices and tables

• Index
• Module Index
• Search Page