Python attributes without boilerplate

https://github.com/hynek/characteristic

Universal encoding detector for Python

https://github.com/chardet/chardet/

Real First Universal Charset Detector

https://github.com/Ousret/charset_normalizer

HTML template engine for Python

https://cheetahtemplate.org/

Highly-optimized, pure-python HTTP server

https://github.com/cherrypy/cheroot

Python framework for command line utilities

https://liw.fi/cliapp/

Python package for creating command line interfaces

https://github.com/mitsuhiko/click

Extend click.Group to invoke a command without explicit subcommand name

https://github.com/click-contrib/click-default-group

Colorization of help messages in Click

https://github.com/click-contrib/click-help-colors

Minimal bindings to GitHub fork of cmark

https://github.com/theacodes/cmarkgfm

Black box testing of Unix programs

https://liw.fi/cmdtest/

Hosted coverage reports for Github, Bitbucket and Gitlab

https://github.com/codecov/codecov-python

Cross-platform API to print colored terminal text from Python apps

https://github.com/tartley/colorama

Command line argument to object parsing library

https://github.com/chrissimpkins/commandlines

CFF subroutinizer for fontTools

https://github.com/googlei18n/compreffor

Drop-in replacement for argparse

https://pypi.org/project/ConfigArgParse/

Simple but powerful config file reader and writer

https://github.com/DiffSK/configobj/

INI style configuration file parser

https://pypi.org/project/configparser/

Provides symbolic constant support to Python projects

https://pypi.org/project/constantly/

Backports and enhancements for the contextlib module

https://pypi.org/project/contextlib2/

Python API for ISO country, subdivision, language and currency

https://pypi.org/project/pycountry/

Coverage plugin to provide sensible default settings

https://github.com/asottile/covdefaults

Code coverage measurement for Python

https://coverage.readthedocs.io/

Enable python coverage for subprocesses

https://github.com/bukzor/python-coverage-enable-subprocess

Show coverage stats online via coveralls.io

https://github.com/TheKevJames/coveralls-python

Iteration support for datetime objects with cron like format

https://pypi.org/project/croniter/

Iteration support for datetime objects with cron like format(2.x)

https://pypi.org/project/croniter/

Cryptographic recipes and primitives for Python developers

https://github.com/pyca/cryptography

Cryptographic recipes and primitives for Python developers

https://github.com/pyca/cryptography

Test vectors for the cryptography package

https://github.com/pyca/cryptography/tree/main/vectors

Cssselect parses CSS3 Selectors and translates them to XPath 1.0

https://github.com/scrapy/cssselect

CSS selectors for Python ElementTree

https://github.com/Kozea/cssselect2

CSS Cascading Style Sheets library for Python

https://github.com/jaraco/cssutils

Cubic-to-quadratic bezier curve conversion

https://github.com/googlei18n/cu2qu

Coroutine-based library for concurrent Python systems programming

https://github.com/dabeaz/curio

Composable style cycles

https://github.com/matplotlib/cycler/

Trivial extension that just raises an exception

https://github.com/twisted/cython-test-exception-raiser

Well-behaved daemon framework for Python

https://pypi.org/project/python-daemon/

Datadog Python library

https://github.com/DataDog/datadogpy

Extensions to the standard Python datetime module

https://dateutil.readthedocs.io

Python bindings for the D-BUS messaging system

https://dbus.freedesktop.org/doc/dbus-python/

Data-Driven Tests for Python Unittest

https://readthedocs.org/projects/ddt/

Better living through Python with decorators

https://github.com/micheles/decorator

Set of flexible objects for representing UFO data

https://github.com/typesupply/defcon

XML bomb protection for Python stdlib modules

https://bitbucket.org/tiran/defusedxml

Library to handle automated deprecations

https://pypi.org/project/deprecation/

Run coverage and linting reports on diffs

https://github.com/Bachmann1234/diff_cover

In-depth comparison of files, archives, and directories

https://diffoscope.org/

Serialize all of python

https://pypi.org/project/dill/

Low-level components of distutils2 and higher-level APIs

https://github.com/pypa/distlib