Python slithers faster by adding lazy imports that load code after startup
Summary
PEP 810, titled “Explicit lazy imports,” has been approved. The proposal, put forward by Pablo Salgadoon and green-lit on 3 November, introduces an opt-in mechanism to defer module loading until symbols are actually used rather than at program startup. The change is designed to speed up startup times — especially for command-line tools and short-lived scripts — while preserving backward compatibility by not making lazy imports the default.
Key Points
- PEP 810 approved (opt-in explicit lazy imports) to let code defer loading modules until needed.
- Lazy imports reduce startup latency — useful for CLIs, small utilities and serverless functions.
- The feature is opt-in to avoid breaking existing behaviour and fragmentation in the ecosystem.
- Earlier PEP 690 tried lazy imports as a default and was rejected over compatibility and fragmentation concerns.
- There were 450+ discussion comments (including naming debates such as `lazy` vs `defer`).
- Implementation will take time to land in mainstream releases; developers can continue to use existing workarounds meanwhile.
Content Summary
Python’s PEP 810 standardises explicit lazy imports so modules can be declared to load only when first used, rather than during initial startup. The idea addresses a long-standing pain point: import statements that are never used still slow down program launch. By making the feature opt-in, the PEP avoids the backward-compatibility and ecosystem-fragmentation problems that sank earlier proposals which tried to make lazy imports the default.
The proposal attracted substantial debate across the community, reflecting how impactful import semantics are for tooling, packaging and runtime expectations. While the Steering Council praised the PEP as striking the right balance, it will be some time before the change becomes widely available in stable Python releases.
Context and Relevance
This matters because startup time is increasingly visible: CLI tools, developer utilities, containers and serverless functions all benefit from faster initialisation. Standardising lazy imports reduces the need for bespoke hacks, forks or ad-hoc solutions across projects and organisations. For maintainers, it also means a formal API and expectations to reason about when modules load and any side effects they cause.
Adoption will influence tooling (linters, debuggers), packaging guidelines and performance best-practices. Teams running many short-lived Python processes or tight startup SLAs should track PEP 810 and plan for migration once the feature is available in supported releases.
Why should I read this?
Short and blunt: if you write Python — especially CLIs, microservices, scripts or serverless code — this is a win. It can shave seconds off startup, unclutter your workaround list, and finally give you a standard way to defer heavy imports. We’ve read the debate and distilled the gist so you don’t have to — worth a skim if you care about performance or packaging headaches.