py.run: __name__ is "builtins", should be "__main__"

[nschloe]

Bug Description

Python's exec() has __name__ set to __main__:

exec("print(__name__)")

__main__

When running the same code through PyO3's py.run(), it'll give builtins.

Steps to Reproduce

See above.

Backtrace

Your operating system and version

Linux 6.12.13-1-lts

Your Python version (python --version)

Python 3.11.11

Your Rust version (rustc --version)

rustc 1.85.0 (4d91de4e4 2025-02-17) (Arch Linux rust 1:1.85.0-1)

Your PyO3 version

v0.23.4

How did you install python? Did you use a virtualenv?

uv venv

Additional Info

No response