`PYO3_PYTHON` and `LD_LIBRARY_PATH` pointing to `venv` are ignored

Bug Description

I would like pyo3 to use the .venv I've created in my python library, when calling functions from that library from rust. - but it ignores the values configured in my environment.

From what I've read I understood it as PYO3_PYTHON and/or LD_LIBRARY_PATH can be used to configure the path to the python interpreter executable. I exported them in the shell and then ran my rust project like so

export PYO3_PYTHON=/path/to/my/python/project/.venv/bin/python
export LD_LIBRARY_PATH=/path/to/my/python/project/.venv/bin/python
cargo run --bin fxctl ping

ping is just a function I use to test the setup. In the rust app, the ping function is invoked through a clap command. The handler looks like so:

use pyo3::prelude::*;

pub fn ping() -> PyResult<()> {
    Python::with_gil(|py| {
        let sys = PyModule::import(py, "sys").unwrap();

        let py_path: String = sys.getattr("executable").unwrap().extract().unwrap();
        let py_version: String = sys.getattr("version").unwrap().extract().unwrap();

        println!("path: {}\nversion: {}", py_path, py_version);
    });
    Ok(())
}

Steps to Reproduce

Reproduction repository:
https://github.com/jakob-lilliemarck/pyo3-python-env-ignored

Backtrace

There is no backtrace as there is no actual error

Your operating system and version

Linux 6.6.65-1-MANJARO #1 SMP PREEMPT_DYNAMIC Wed Dec 11 22:24:04 UTC 2024 x86_64 GNU/Linux

Your Python version (python --version)

3.12.7 (main, Oct 1 2024, 11:15:50) [GCC 14.2.1 20240910]

Your Rust version (rustc --version)

rustc 1.85.0-nightly (a224f3807 2024-12-09)

Your PyO3 version

0.23.3

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

Can't recall, but from the looks of it I installed the global one using brew, then I created a virtual env in my project by python -m venv .venv

Additional Info

No response

Start with the linked reproduction repository and inspect how PyO3 0.23.3 discovers and configures the Python interpreter and library paths during the Cargo build and runtime. Reproduce the reported PYO3_PYTHON and LD_LIBRARY_PATH environment, then compare the selected executable and version with the expected .venv; done means the behavior is corrected or clearly documented with a regression test.