PEP 810 – Explicit lazy imports

Summary

PEP 810 – Explicit lazy imports Author: Pablo Galindo <pablogsal at python.org>, Germán Méndez Bravo <german.mb at gmail.com>, Thomas Wouters <thomas at python.org>, Dino Viehland <dinoviehland at gmail.com>, Brittany Reynoso <brittanyrey at gmail.com>, Noah Kim <noahbkim at gmail.com>, Tim Stumbaugh <me at tjstum.com> Discussions-To: Discourse thread Status: Draft Type: Standards Track Created: 02-Oct-2025 Python-Version: 3.15 Post-History: 03-Oct-2025 This PEP introduces syntax for lazy imports as an explicit language feature: lazy import json lazy from json import dumps Lazy imports defer the loading and execution of a module until the first time the imported name is used, in contrast to ‘normal’ imports, which eagerly load and execute a module at the point of the import statement. By allowing developers to mark individual imports as lazy with explicit syntax, Python programs can reduce startup time, memory usage, and unnecessary work. This is particularly beneficial for command-line tools, test suites, and applications with large dependency graphs. This proposal preserves full backwards compatibility: normal import statements remain unchanged, and lazy imports are enabled only where explicitly requested. The dominant convention in Python code is to place all imports at the module level, typically at the beginning of the file. This avoids repetition, makes import dependencies clear and minimizes runtime overhead by only evaluating an import statement once per module. A major drawback with this approach is that importing the first module for an execution of Python (the “main” module) often triggers an immediate cascade of imports, and optimistically loads many dependencies that may never be used. The effect is especially costly for command-line tools with multiple subcommands, where even running the command with --help can load dozens of unnecessary modules and take several seconds. This basic example demonstrates what must be loaded just to get helpful feedback t...