does importing a module more then once affects runtime?

[raisfeld-ori]

i am rewriting some of my modules in rust, and while creating them, i noticed i have a specific function that gets imported only for that function, since it is necessary for that function only, something like

def function():
    from foo import bar
    # the rest of the code

this isn't an issue in python, since runtime doesn't get affected if you import a module that has already been imported, but since pyo3 isn't exactly normal python, i am wondering if the same thing is true here, if i were to import a module inside a function, for example

#[pyfunction]
fn function(){
    Python::with_gil(|py|{
        let foo = py.import("foo");
        // the rest of the code
})
}

would this affect the runtime speed by any way?

[adamreichold]

Since our import method calls into the usual Python machinery, I don't see a difference if you import foo from Rust or Python code.

[raisfeld-ori]

i thought *.pyd files are *.dll files with extra requirements, are you sure the effect at runtime is the same?

[adamreichold]

Maybe I misunderstood your question: Are you asking about the effect of importing some module foo from your Rust code? Or are you asking about repeatedly importing your Rust-written extension foo?

If you are talking about repeatedly import a Rust extension than we prevented this until recently where we relaxed the check to prevent only usage in multiple sub-interpreters but made multiple imports a no-op, c.f. #3446

Hence, it will also not have any effect performance effect besides the cost of running the import itself.