Sample code for: Python 3.15 Preview: Lazy Imports

[stephengruppetta]

Sample code for the Real Python tutorial Python 3.15 Preview: Lazy Imports.

• Tutorial PR: https://github.com/realpython/tutorial-drafts/pull/1193
• Trello: https://trello.com/c/KRhsCcHM

Standard library only, but it needs Python 3.15 — most files use the lazy keyword from PEP 810, which is a SyntaxError on anything earlier. Every file here was run against a CPython 3.15.0rc1 build, and the tutorial quotes its real output.

Layout

Path	Section
noisy_module.py, probe.py	Defer a Whole Module
shapes.py, partial.py	Defer a Name From a Module
badfunc.py	Find Out Where lazy Isn't Allowed
report_cli/	Speed Up a Real CLI
type_checking_guard.py, lazy_annotation.py	Retire the if TYPE_CHECKING Dance
fail.py	Read a Deferred Import Error
circular/	Don't Expect a Circular Import Fix
bridge.py, allmode.py	Go Lazy Without the Keyword

report_cli/ holds three versions of the same CLI: cli_eager.py, cli_lazy.py (five lazy keywords, nothing else changed), and cli_too_lazy.py, which also defers the two plugin imports and so silently empties the format registry. bench.py times any of them, and a --load-all flag reads every deferred name so you can check that deferral costs nothing once the modules are used.

circular/ has four self-contained folders: eager/ fails, lazy/ is fixed by deferring one side, and init_eager/ + init_lazy/ both fail with the same ImportError because the cycle needs a value during module initialization.

One change outside the new folder

pyproject.toml adds python315-lazy-imports to ruff's exclude list. Two reasons:

1. ruff 0.14.1 can't parse the lazy keyword. ruff format --check fails with invalid-syntax: Simple statements must be separated by newlines or semicolons on any file using it, which would break CI.
2. With the folder excluded, the files can follow the Real Python style guide's blank-line rules — one blank line between definitions, not PEP 8's two — so the snippets in the tutorial and the files in this folder stay byte-identical.

CI passes locally with the exclusion in place: ruff format --check, ruff check, and dircheck.py are all green.