Is it possible to make the python binding optional feature?

[NMZ0429]

I am making a crate for both python and rust user. The structure of my crate is like below.

├── src
│   ├── lib.rs <- python binding
│   ├── core.rs <- pure rust functions

Currently, all rust functions are in core.rs and I wrapped them by another functions in lib.rs to use #[pyfunction] and #[pymodule] macros.

My question is that if it is possible to seperate the code for binding from lib.rs to another file and it only compiles only when user wants to use python binding. So ideally, it would be something like below.

├── src
│   ├── lib.rs
│   ├── python_binding.rs <- for python user
│   ├── core.rs <- pure rust functions

So if user compild it with a feature flag, python_binding.rs is exposed and compiled. Otherwise, it is not compiled and user can only use pure rust functions in core.rs.

[mejrs]

Yes, you can do that. You just need to make pyo3 an optional dependency and use a bunch of cfg_attr's.

[NMZ0429]

Thank you for your answer. Could you elaborate it a bit more?
I actually tried to put #[cfg(feature = "python")] above #[pyfunction] and #[pymodule] then compile it with maturin develop --features python but it somehow raises segmentation fault at runtime in python.

Likely, my Cargo.toml is not correct. Could you please take a look at it?

[dependencies]
pyo3 = "0.19.0"
itertools = "0.10.1"
hashbrown = "0.14"
rand = "0.8.4"

[features]
python = [] 

My crate works after removing the feature flag and #[cfg(feature = "python")] .

[birkenfeld]

Can you reduce this to a minimal example and post it (all files including Carogo.toml)? It is hard to debug or reproduce without knowing how exactly you apply the feature.

[NMZ0429]

Thank you for your help. I eventually solved the problem by enabling extension-module feature of pyo3. So that Cargo.toml should look like below.

[dependencies]
pyo3 = { version = "0.19.0", optional = true, features = ["extension-module"] }

[features]
default = []
python = ["pyo3"]