stdlibs 2026.2.26

List of packages in the stdlib

stdlibs

Simple list of top-level packages in Python's standard library

This package provides a static listing of all known modules in the Python standard library, with separate lists available for each major release dating back to Python 2.3. It also includes combined lists of all module names that were ever available in any 3.x release, any 2.x release, or both.

Note: On Python versions 3.10 or newer, a list of module names for the active runtime is available sys.stdlib_module_names. This package exists to provide an historical record, including pre-release listings, for use with static analysis and other tooling. It also captures a number of "private", importable modules that ship with stable releases, but that aren't generally included in the official stdlib_module_names.

This package only includes listings for CPython releases. If other runtimes would be useful, open an issue and start a discussion on how best that can be accomodated.

stdlibs is used by:

• Ruff
• µsort

Install

You can install it from PyPI:

$ pip install stdlibs

Usage

The recommended usage is to reference stdlibs.module_names — the top-level names that are valid in some version of Python 3.x on some platform. This is a superset of top-level names you may have, and a superset of those in sys.stdlib_module_names.

>>> from stdlibs import module_names
>>> print("os" in module_names)
True
>>> print("zoneinfo" in module_names)  # 3.9+
True

If you need a specific version, those are available as other modules:

>>> from stdlibs.py36 import module_names as module_names_py36
>>> print("os" in module_names_py36)
True
>>> print("zoneinfo" in module_names_py36)
False

If you intend to process more than one version, you may find the string api easier:

>>> from stdlibs import stdlib_module_names, KNOWN_VERSIONS
>>> [v for v in KNOWN_VERSIONS if "dataclasses" in stdlib_module_names(v)]
['3.7', '3.8', '3.9', '3.10', '3.11', '3.12', '3.13', '3.14', '3.15']
>>>
>>> sorted(stdlib_module_names("3.7") - stdlib_module_names("3.6"))
['_abc', '_contextvars', '_py_abc', '_queue', '_uuid', '_xxtestfuzz', 'contextvars', 'dataclasses']
>>>
>>> from moreorless.click import unified_diff
>>> prev = None
>>> buf = []
>>> for v in KNOWN_VERSIONS:
...     cur = ''.join([f"{name}\n" for name in sorted(stdlib_module_names(v))])
...     if prev:
...         buf.append(unified_diff(prev, cur, f"new-in-{v}"))
...     prev = cur
>>> print(''.join(''.join(buf).splitlines(True)[:10]), end='')
--- a/new-in-2.4
+++ b/new-in-2.4
@@ -19,7 +19,6 @@
 DocXMLRPCServer
 ERRNO
 EasyDialogs
-FCNTL
 FILE
 FL
 FileDialog

Regenerating

If there might have been new release tarballs, first execute stdlibs.fetch_releases which will update stdlibs/releases.toml.

Then execute stdlibs.fetch which will download all those release tarballs, and create/update the appropriate stdlibs/py*.py files with the changes. A fresh run takes about two minutes, but is much faster on subsequent runs.

$ make distclean virtualenv
$ source .venv/bin/activate
(.venv) $ python -m stdlibs.fetch_releases
(.venv) $ python -m stdlibs.fetch

License

stdlibs is copyright Amethyst Reese, and licensed under the MIT license. I am providing code in this repository to you under an open source license. This is my personal repository; the license you receive to my code is from me and not from my employer. See the LICENSE file for details.