How PEP 810’s Explicit Lazy Imports Can Speed Up Your Python Apps

Note: After lengthy debate in the Python developer community, PEP 810 has been approved.

PEP 810, titled “Explicit Lazy Imports”, aims to make Python programs start faster by allowing scripts to defer loading imported libraries until they are actually needed, rather than loading them at startup.

PEP 810 proposal: https://pep-previews--4622.org.readthedocs.build/pep-0810/

The enhancement introduces lazy imports into the Python language itself as an optional feature.

Importing modules in Python is both beneficial and costly. A few import statements can greatly extend a program’s functionality, but imported symbols that are never used increase startup time. For example, running python setup.py --help loads imports that may not be needed.

As a solution, lazy imports defer loading of certain content until it is actually required.

This idea is not new, yet it is surprising that the standard implementation took so long. Many methods for lazy importing exist, but Python has never had this capability built‑in.

Previous attempts, such as PEP 690, were rejected mainly because they made lazy imports the default behavior, raising concerns about community fragmentation and backward compatibility. Developers created their own workarounds, and some organizations even forked CPython.

The success of PEP 810 lies in making lazy imports an optional feature, standardizing the previously scattered custom solutions while preserving backward compatibility.