Derive Macro PyEnum 

#[derive(PyEnum)]
{
    // Attributes available to this derive:
    #[pyenum]
}

Derive a pyenum::PyEnum implementation for a unit-variant Rust enum.

The derive also emits PyO3 0.28 IntoPyObject<'py> (for T and &T) and FromPyObject<'a, 'py> impls, so the Rust enum can appear directly in #[pyfunction], #[pymethods], and #[pyclass] field signatures.

Attributes

Enum-level (all optional):

• #[pyenum(base = "Enum" | "IntEnum" | "StrEnum" | "Flag" | "IntFlag")] — select the Python base class. Defaults to "Enum".
• #[pyenum(name = "...")] — override the Python class name. Defaults to the Rust enum identifier.

Variant-level (optional, mutually exclusive with a Rust discriminant):

• #[pyenum(value = "...")] — explicit Python string value. Valid on StrEnum (and Enum). Without it, StrEnum variants default to Python’s auto() semantics, which lowercase the variant name.

Example

use pyenum::{PyEnum, PyModuleExt};
use pyo3::prelude::*;

#[derive(Clone, Copy, PyEnum)]
#[pyenum(base = "IntEnum")]
pub enum HttpStatus {
    Ok = 200,
    NotFound = 404,
}

#[pyfunction]
fn classify(s: HttpStatus) -> HttpStatus { s }

#[pymodule]
fn demo(m: &Bound<'_, PyModule>) -> PyResult<()> {
    m.add_enum::<HttpStatus>()?;
    m.add_function(wrap_pyfunction!(classify, m)?)
}

Rejected at compile time

The macro emits spanned compile_error! diagnostics for:

• Tuple / struct variants, generics, lifetimes, and empty enums.
• Variant names colliding with Python keywords, dunders, or enum.Enum-reserved attributes.
• Base/value shape mismatches (e.g. #[pyenum(value = "x")] on IntEnum, or an integer discriminant on StrEnum).
• Duplicate resolved values — includes the auto() vs. explicit collision on every integer-shaped base (enum { A, B = 1 } with base IntEnum, enum { Read, Write = 1 } with base Flag, etc.) and auto-lowercased name collisions on StrEnum (Hello + HELLO).
• Duplicate or unknown #[pyenum(...)] keys.