lazysafe

safely adopt python 3.15 lazy imports.

why it exists

python 3.15 ships PEP 810 explicit lazy imports. lazy import json defers loading until first use. reported wins: ~2.9x faster startup for import-heavy applications.

the catch: laziness changes when import-time side effects run. some libraries depend on them. under lazy mode, programs break in confusing ways.

lazysafe answers that question empirically.

install

pip install lazysafe

quickstart

# see which imports are safe to make lazy
lazysafe analyze src/

# show all modules including safe ones
lazysafe analyze src/ --all

# measure startup time
lazysafe measure python -m myapp --budget 500

what it does

lazysafe scans your Python source files and classifies every import statement by its side-effect risk:

finding meaning action
SAFE no side effects detected safe to make lazy
RISKY might have side effects investigate before lazy
UNSAFE side effect detected keep eager
UNKNOWN can't determine statically needs further investigation

side-effect rules

code what it detects confidence
SE01 module-level function calls 0.6
SE02 foreign attribute assignment (monkeypatching) 0.9
SE03 sys.path / sys.modules / os.environ mutation 0.95
SE04 atexit / signal / logging registration 0.85-0.9
SE05 module-level file I/O 0.8
SE06 framework registration decorators (2+) 0.5
SE07 importlib.import_module with computed names 0.9
SE08 try/except ImportError with fallback patches 0.7

what it does not do

  • runtime lazy-loading for older pythons (no backport of PEP 810)
  • patching third-party packages' code
  • general linting/formatting (use ruff)

requirements

  • python >= 3.11 (host running lazysafe)
  • target programs using lazy import semantics require python >= 3.15
  • linux, macos, windows

links

license

MIT

Project links

Data verified by PyPI on Sep 9, 2026
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Key dates

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  • Released:
Newer release available (0.3.0)

1 maintainer

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Avatar for rahulXs from gravatar.com rahulXs

Credits

Author: Rahul Sharma

GitHub Statistics

Data verified by PyPI on Sep 9, 2026
The GitHub source repository was provided by the project maintainers and verified by PyPI at the time of upload. Stars, forks, and open issues/PRs are derived from that repository and have not been independently verified.

License

MIT License (MIT)

Requires

Python >=3.11

Tags

cpython315 import-time lazy-imports pep810 performance python side-effects startup verification

Classifiers

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