uu and the uu encoding

The uu module provides uuencode format, an old binary encoding format for email from 1980. The uu format has been replaced by MIME. The uu codec is provided by the binascii module. There’s also encodings/uu_codec.py which is a codec for the same encoding; it should also be deprecated.

xdrlib

The xdrlib module supports the Sun External Data Representation Standard. XDR is an old binary serialization format from 1987. These days it’s rarely used outside specialized domains like NFS.

aifc

The aifc module provides support for reading and writing AIFF and AIFF-C files. The Audio Interchange File Format is an old audio format from 1988 based on Amiga IFF. It was most commonly used on the Apple Macintosh. These days only few specialized application use AIFF.

A user disclosed [6] that the post production film industry makes heavy use of the AIFC file format. The usage of the aifc module in closed source and internal software was unknown prior to the first posting of this PEP. This may be a compelling argument to keep the aifc module in the standard library. The file format is stable and the module does not require much maintenance. The strategic benefits for Python may outmatch the burden.

audioop

The audioop module contains helper functions to manipulate raw audio data and adaptive differential pulse-code modulated audio data. The module is implemented in C without any additional dependencies. The aifc, sunau, and wave modules depend on audioop for some operations.

The byteswap operation in the wave module can be substituted with little extra work. In case aifc is not deprecated as well, a reduced version of the audioop module is converted into a private implementation detail, e.g. _audioop with byteswap, alaw2lin, ulaw2lin, lin2alaw, lin2ulaw, and lin2adpcm.

chunk

The chunk module provides support for reading and writing Electronic Arts’ Interchange File Format. IFF is an old audio file format originally introduced for Commodore and Amiga. The format is no longer relevant.

imghdr

The imghdr module is a simple tool to guess the image file format from the first 32 bytes of a file or buffer. It supports only a limited number of formats and neither returns resolution nor color depth.

ossaudiodev

The ossaudiodev module provides support for Open Sound System, an interface to sound playback and capture devices. OSS was initially free software, but later support for newer sound devices and improvements were proprietary. Linux community abandoned OSS in favor of ALSA [1]. Some operating systems like OpenBSD and NetBSD provide an incomplete [2] emulation of OSS.

To best of my knowledge, FreeBSD is the only widespread operating system that uses Open Sound System as of today. The ossaudiodev hasn’t seen any improvements or new features since 2003. All commits since 2003 are project-wide code cleanups and a couple of bug fixes. It would be beneficial for both FreeBSD community and core development, if the module would be maintained and distributed by people that care for it and use it.

The standard library used to have more audio-related modules. The other audio device interfaces (audiodev, linuxaudiodev, sunaudiodev) were removed in 2007 as part of the PEP 3108 stdlib re-organization.

sndhdr

The sndhdr module is similar to the imghdr module but for audio formats. It guesses file format, channels, frame rate, and sample widths from the first 512 bytes of a file or buffer. The module only supports AU, AIFF, HCOM, VOC, WAV, and other ancient formats.

sunau

The sunau module provides support for Sun AU sound format. It’s yet another old, obsolete file format.

asynchat

The asynchat module is built on top of asyncore and has been deprecated since Python 3.6.

asyncore

The asyncore module was the first module for asynchronous socket service clients and servers. It has been replaced by asyncio and is deprecated since Python 3.6.

The asyncore module is also used in stdlib tests. The tests for ftplib, logging, smptd, smtplib, and ssl are partly based on asyncore. These tests must be updated to use asyncio or threading.

cgi

The cgi module is a support module for Common Gateway Interface (CGI) scripts. CGI is deemed as inefficient because every incoming request is handled in a new process. PEP 206 considers the module as:

“[…] designed poorly and are now near-impossible to fix (cgi) […]”

Replacements for the various parts of cgi which are not directly related to executing code are:

• parse with urllib.parse.parse_qs (parse is just a wrapper)
• parse_header with email.message.Message (see example below)
• parse_multipart with email.message.Message (same MIME RFCs)
• FieldStorage/MiniFieldStorage has no direct replacement, but can typically be replaced by using multipart (for POST and PUT requests) or urllib.parse.parse_qsl (for GET and HEAD requests)
• valid_boundary (undocumented) with re.compile("^[ -~]{0,200}[!-~]$")

As an explicit example of how close parse_header and email.message.Message are:

>>> from cgi import parse_header
>>> from email.message import Message
>>> parse_header(h)
('application/json', {'charset': 'utf8'})
>>> m = Message()
>>> m['content-type'] = h
>>> m.get_params()
[('application/json', ''), ('charset', 'utf8')]
>>> m.get_param('charset')
'utf8'

cgitb

The cgitb module is a helper for the cgi module for configurable tracebacks.

The cgitb module is not used by any major Python web framework (Django, Pyramid, Plone, Flask, CherryPy, or Bottle). Only Paste uses it in an optional debugging middleware.

smtpd

The smtpd module provides a simple implementation of a SMTP mail server. The module documentation marks the module as deprecated and recommends aiosmtpd instead. The deprecation message was added in releases 3.4.7, 3.5.4, and 3.6.1.

nntplib

The nntplib module implements the client side of the Network News Transfer Protocol (nntp). News groups used to be a dominant platform for online discussions. Over the last two decades, news has been slowly but steadily replaced with mailing lists and web-based discussion platforms. Twisted is also planning to deprecate NNTP support and pynntp hasn’t seen any activity since 2014. This is a good indicator that the public interest in NNTP support is declining.

The nntplib tests have been the cause of additional work in the recent past. Python only contains the client side of NNTP, so the tests connect to external news servers. The servers are sometimes unavailable, too slow, or do not work correctly over IPv6. The situation causes flaky test runs on buildbots.

telnetlib

The telnetlib module provides a Telnet class that implements the Telnet protocol.

crypt

The crypt module implements password hashing based on the crypt(3) function from libcrypt or libxcrypt on Unix-like platforms. The algorithms are mostly old, of poor quality and insecure. Users are discouraged from using them.

• The module is not available on Windows. Cross-platform applications need an alternative implementation anyway.
• Only DES encryption is guaranteed to be available. DES has an extremely limited key space of 2**56.
• MD5, salted SHA256, salted SHA512, and Blowfish are optional extensions. SSHA256 and SSHA512 are glibc extensions. Blowfish (bcrypt) is the only algorithm that is still secure. However it’s in glibc and therefore not commonly available on Linux.
• Depending on the platform, the crypt module is not thread safe. Only implementations with crypt_r(3) are thread safe.
• The module was never useful to interact with system user and password databases. On BSD, macOS, and Linux, all user authentication and password modification operations must go through PAM (pluggable authentication module); see the spwd deprecation.

nis

The nis module provides NIS/YP support. Network Information Service / Yellow Pages is an old and deprecated directory service protocol developed by Sun Microsystems. Its designed successor NIS+ from 1992 never took off. For a long time, libc’s Name Service Switch, LDAP, and Kerberos/GSSAPI have been considered a more powerful and more secure replacement for NIS.

spwd

The spwd module provides direct access to Unix shadow password database using non-standard APIs.

In general, it’s a bad idea to use spwd. It circumvents system security policies, does not use the PAM stack, and is only compatible with local user accounts, because it ignores NSS. The use of the spwd module for access control must be considered a security bug, as it bypasses PAM’s access control.

Furthermore, the spwd module uses the shadow(3) APIs. Functions like getspnam(3) access the /etc/shadow file directly. This is dangerous and even forbidden for confined services on systems with a security engine like SELinux or AppArmor.

msilib

The msilib package is a Windows-only package. It supports the creation of Microsoft Installers (MSI). The package also exposes additional APIs to create cabinet files (CAB). The module is used to facilitate distutils to create MSI installers with the bdist_msi command. In the past it was used to create CPython’s official Windows installer, too.

Microsoft is slowly moving away from MSI in favor of Windows 10 Apps (AppX) as a new deployment model [3].

pipes

The pipes module provides helpers to pipe the input of one command into the output of another command. The module is built on top of os.popen. Users are encouraged to use the subprocess module instead.