UFO font processing library

https://github.com/fonttools/ufoLib2

UFO source file linter

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

Script to normalize the XML and other data inside of a UFO

https://github.com/unified-font-object/ufoNormalizer

Read, write and generate UFOs with designspace data

https://github.com/LettError/ufoProcessor

Streamlined Cython bindings for the harfbuzz shaping engine

https://github.com/harfbuzz/uharfbuzz

Ultra fast JSON encoder and decoder for Python

https://github.com/esnme/ultrajson

Simple package

https://github.com/Carreau/undefined

Unicodedata backport updated to the latest Unicode version

https://github.com/fonttools/unicodedata2

ASCII transliterations of Unicode text

https://pypi.org/project/Unidecode/

Python library to parse and interact with unified diff data

https://github.com/matiasb/python-unidiff

New features in unittest backported to Python 2

https://github.com/garbas/unittest2

Cross-platform uptime library

https://github.com/Cairnarvon/uptime

Python implementation of URI Template

https://github.com/python-hyper/uritemplate

RFC 3986 compliant, Unicode-aware, scheme-agnostic replacement for urlparse

https://github.com/tkem/uritools

URL normalization for Python

https://github.com/niksite/url-normalize

HTTP library with thread-safe connection pooling, file post, and more

https://github.com/urllib3/urllib3

Python wrapper around libusb

http://pyusb.github.io/pyusb/

Verifies if an email address is valid and really exists

https://github.com/syrusakbary/validate_email

Python module to validate VAT numbers

http://code.google.com/p/vatnumber/

Easy VCS-based management of project version strings

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

Obtain package version from repo tags

https://github.com/jwodder/versioningit

User-friendlier way to use Harfbuzz in Python

https://github.com/simoncozens/vharfbuzz

Tool for creating isolated Python environments

https://virtualenv.pypa.io

Navigate HTTP resources using WADL files as guides

https://launchpad.net/wadllib

Python WSGI server

https://docs.pylonsproject.org/projects/waitress/en/latest/ https://github.com/Pylons/waitress

Python API library to monitor file system events

https://github.com/gorakhargosh/watchdog

Wildcard/glob file name matcher

https://pypi.org/project/wcmatch/

Determine the printable width of the terminal

https://github.com/jquast/wcwidth

Converts HTML/CSS documents to PDF

https://weasyprint.org/

Character encoding aliases for legacy web content

https://github.com/SimonSapin/python-webencodings

WSGI request and response Python object

https://webob.org/

Websocket client for python

https://github.com/websocket-client/websocket-client

Implementation of the WebSocket Protocol (RFC 6455 and 7692)

https://pypi.org/project/websockets/ https://github.com/python-websockets/websockets

Helper to test WSGI applications

https://docs.pylonsproject.org/projects/webtest/en/latest/ https://github.com/Pylons/webtest

Python utilities collection for building WSGI applications

https://palletsprojects.com/p/werkzeug/ https://github.com/pallets/werkzeug

Built-package format for Python

https://github.com/pypa/wheel

Decorators, wrappers and monkey patching

https://github.com/GrahamDumpleton/wrapt

WebSocket Accelerator for ws4py and AutobahnPython

https://github.com/methane/wsaccel

Sans-IO WebSocket protocol implementation

https://pypi.org/project/wsproto/

Xcffib is a replacement for xpyb, also is a XCB python binding

https://github.com/tych0/xcffib

Python library to access freedesktop.org standards

https://freedesktop.org/wiki/Software/pyxdg/

Implementation of XML Schema for Python

https://pypi.org/project/xmlschema/

XML parser that returns python dictionaries

https://pypi.org/project/xmltodict/

Python bindings for the xxHash library

https://github.com/ifduyue/python-xxhash

Python YAML parser

https://pyyaml.org/

Linter for YAML files

https://github.com/adrienverge/yamllint

Yet another URL library

https://github.com/aio-libs/yarl

Interface to the Unicode Character Database

https://github.com/simoncozens/youseedee

Python module to retrieve stock quote data from Yahoo Finance

https://github.com/cgoldberg/ystockquote

Basic inter-process locks

https://pypi.org/project/zc.lockfile/