Guide docs for all protocol methods

[davidhewitt]

Just thinking that for the guide it would be nice to add a table to the #[pyproto] section listing all the dunder methods that can be implemented and the protocols they are a part of (e.g. __int__ -> PyNumberProtocol etc.)

[davidhewitt]

Please note for anyone who looks at this that the #[pyproto] methods are planned to be merged into #[pymethods], see #1206

[davidhewitt]

After #[pymethods] are ready, the docs we need will probably be very similar to these excellent ones for Cython: https://cython.readthedocs.io/en/latest/src/userguide/special_methods.html

[birkenfeld]

I volunteer for that.

[davidhewitt]

Thanks! I think @mejrs also expressed desire to write something in #1864 ? You might want to double-check you don't end up duplicating effort.

[mejrs]

I'm leaning towards this:

• A table at https://pyo3.rs/main/doc/pyo3/attr.pymethods.html summarizing all the dunders like https://cython.readthedocs.io/en/latest/src/userguide/special_methods.html#special-method-table
• Examples in the guide, like https://pyo3.rs/main/class.html?#callable-objects We might want to structure that in a different way .e.g. a chapter for each protocol.

[birkenfeld]

Sounds good to me. There is extensive material on the Python side on how these protocols work, and we should mainly state what we support and what the Rust/PyO3-specific snags are.

[davidhewitt]

We now have https://pyo3.rs/v0.20.0/class/protocols, plus some more detailed examples by @mejrs and @birkenfeld for specific protocols. I'm going to close this one as resolved, though of course more documentation improvements are always possible!