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/

Create projects from cookiecutters (project templates)

https://pypi.org/project/cookiecutter/

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

Collection of C++ headers to write Python C extension modules

https://pypi.python.org/pypi/cppy

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

CSS related utilities (parsing, serialization, etc) for python

https://github.com/ebook-utils/css-parser

Python port of YUI CSS Compressor

https://github.com/sprymix/csscompressor

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

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

Remove TrueType instruction sets (hints) in fonts

https://github.com/source-foundry/dehinter

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/

Do dirty (but extremely useful) things with equals

https://dirty-equals.helpmanual.io/latest/ https://github.com/samuelcolvin/dirty-equals

Low-level components of distutils2 and higher-level APIs

https://github.com/pypa/distlib

Linux OS platform information API

https://github.com/nir0s/distro

User registration with social account authentication

https://allauth.org/ https://docs.allauth.org/en/latest/ https://github.com/pennersr/django-allauth

Configurable set of panels to display debug information

https://django-debug-toolbar.readthedocs.io/en/latest/ https://github.com/jazzband/django-debug-toolbar

Lightweight app for interacting with gravatars

https://github.com/twaddington/django-gravatar

Django library to help interaction with Mailman

https://gitlab.com/mailman/django-mailman3

Django Debug Toolbar panel for Requests

https://github.com/marceltschoppch/django-requests-debug-toolbar

High-level Python Web Framework

https://www.djangoproject.com/

High-level Python Web Framework

https://www.djangoproject.com/

Python library for DKIM email signing and verification

https://launchpad.net/dkimpy

Manipulate DNS records on various DNS providers in a standardized way

https://github.com/AnalogJ/lexicon