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Python 3.15 lazy imports can avoid plugin-related startup costs

simonwillison.net 5 min read Editor score 7/10

Python 3.15’s explicit lazy imports defer loading modules until their symbols are used; the author says heavy plugin dependencies had added multiple seconds to CLI startup. This feature could reduce startup overhead in extensible Python tools.

What

Python 3.15 adds explicit lazy imports, which defer importing a module until its symbols are first used.

How

The feature can avoid loading heavy plugin dependencies at startup; the release also adds a low-overhead sampling profiler to the standard library.

Why it matters

Lazy imports can reduce startup work in plugin-based tools, while sampling profiles help engineers inspect running processes with little overhead.

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