Previous Work

The groundwork for this proposal was established with PEP 527, which proposed deprecating and eventually removing upload support for a handful of un(der)used file extensions and distribution types.

In particular, PEP 527 proposed the removal of the bdist_dumb, bdist_rpm, bdist_dmg, bdist_msi, and bdist_wininst distribution types, as well as the .tar, .tar.bz2, .tar.xz, .tar.Z, .tgz, and .tbz file extensions on distribution filenames.

PEP 527 was fully enacted with PR #7529 to Warehouse, which was merged on 13 April 2020.

The bdist_egg format

The bdist_egg filetype identifies distributions in the egg format. The egg format was introduced by setuptools in 2004 and is roughly equivalent in functionality to the wheel format first introduced by PEP 427 in 2012 as the standardized format for built distributions.

Despite its longevity, the egg format has had limited adoption on PyPI. Some observations from that issue:

• In the month of May 2023, bdist_egg uploads accounted for 0.2% of all distribution uploads to PyPI;
• pip deprecated its --egg option in 2016;
• setuptools has considered egg support deprecated since 2019;
• build only supports the sdist and bdist_wheel filetypes.

Given the above, this PEP proposes the removal of the bdist_egg format under the same justifications presented in PEP 527, namely:

• Egg distributions are of limited use to the broader ecosystem and therefore represent a non-reciprocal maintenance burden;
• Having an additional built distribution format is confusing to end users, who may mistakenly pick it over the wheel format;

This PEP additionally offers an argument for removal rooted in standardization and duplication: the egg format is not standardized by any PEP or other community standard, and overlaps heavily with its standardized and well-supported alternative (wheel).

The .egg file extension

The .egg file extension is used exclusively for distributions of the bdist_egg format. As such, it serves no purpose in a scenario where PyPI disables new distribution uploads for bdist_egg distributions.

Prior Art

The removal process above was based on that of PEP 527, with the following changes:

• All projects will be continue to be allowed to upload eggs during the deprecation period, not just those that have done so previously.
• Uploading an egg during the deprecation period will also trigger an email to maintainers, in addition to the one-time email at the beginning.

Limited Impact

As noted in the rationale section, this PEP is expected to have no impact on the overwhelming majority of PyPI users and projects, and there has been substantial community coordination over the past 1 1/2 years to minimize the impact on the few last use cases.

Hosted Files

This PEP does NOT propose the removal of any egg distributions that have already been uploaded to PyPI. All previously uploaded egg distributions will remain downloadable, ensuring that existing users will continue to be able to download them.

Deprecation Period

This PEP uses the removal process documented above, which specifies a deprecation period of 1 month for projects that have previously uploaded egg distributions to PyPI.

After the end of the deprecation period, support for uploading new egg distributions will cease to exist on PyPI.