docs: major rewrite for Bound API #3906

davidhewitt · 2024-02-26T23:24:04Z

I started these on the weekend but ran out of time to go any further, I'll try to continue with these in the next couple of days...

guide/src/python_from_rust/calling-existing-code.md

guide/src/python_from_rust.md

codspeed-hq · 2024-03-08T12:21:24Z

CodSpeed Performance Report

Merging #3906 will not alter performance

_{Comparing davidhewitt:bound-docs (0547c63) with main (14d1d2a)}

🎉 Hooray! `pytest-codspeed` just leveled up to 2.2.0!

A heads-up, this is a breaking change and it might affect your current performance baseline a bit. But here's the exciting part - it's packed with new, cool features and promises improved result stability 🥳!
Curious about what's new? Visit our releases page to delve into all the awesome details about this new version.

Summary

✅ 67 untouched benchmarks

Icxolu · 2024-03-08T22:09:20Z

guide/src/python_from_rust.md


-* [`call`]({{#PYO3_DOCS_URL}}/pyo3/prelude/trait.PyAnyMethods#tymethod.call) - call any callable Python object.
-* [`call_method`]({{#PYO3_DOCS_URL}}/pyo3/prelude/trait.PyAnyMethods#tymethod.call_method) - call a method on the Python object.
+* It provides global APIs for the Python interpreter, such as [`py.eval()`][eval] and [`py.import()`][import].


Suggested change

* It provides global APIs for the Python interpreter, such as [`py.eval()`][eval] and [`py.import()`][import].

* It provides global APIs for the Python interpreter, such as [`py.eval_bound()`][eval] and [`py.import_bound()`][import].

guide/src/python_from_rust.md

Icxolu · 2024-03-08T22:30:57Z

guide/src/types.md


-## The Python GIL, mutability, and Rust types
+These smart pointers have different numbers of lifetime parameters, which defines how they behave. `Py<T>` has no lifetime parameters, `Bound<'py, T>` has a lifetime parameter `'py`, and `Borrowed<'a, 'py, T>` has two lifetime parameters `'a` and `'py`.


If we make a point here about these, we should also explain what these lifetimes describe, not just that they are there.
What does 'py describe? Is it the same for Bound and Borrowed? What about 'a?

Or we remove this here and defer to the detail sections below.

Tried to expand on this a bit.

guide/src/types.md

guide/src/python_from_rust/calling-existing-code.md

MarshalX · 2024-03-10T00:29:02Z

guide/src/types.md

+
+By having the binding to the `'py` lifetime, `Bound<'py, T>` can offer the complete PyO3 API at maximum efficiency. This means that in almost all cases where `Py<T>` is not necessary for lifetime reasons, `Bound<'py, T>` should be used.
+
+`Bound<'py, T>` engages in Python reference counting. This means that `Bound<'py, T>` owns a Python object. Rust code which just wants to borrow a Python object should use a shared reference `&Bound<'py, T>`. Just like `std::sync::Arg`, using `.clone()` and `drop()` will cheaply implement and decrement the reference count of the object (just in this case, the reference counting is implemented by the Python interpreter itself).


Suggested change

`Bound<'py, T>` engages in Python reference counting. This means that `Bound<'py, T>` owns a Python object. Rust code which just wants to borrow a Python object should use a shared reference `&Bound<'py, T>`. Just like `std::sync::Arg`, using `.clone()` and `drop()` will cheaply implement and decrement the reference count of the object (just in this case, the reference counting is implemented by the Python interpreter itself).

`Bound<'py, T>` engages in Python reference counting. This means that `Bound<'py, T>` owns a Python object. Rust code which just wants to borrow a Python object should use a shared reference `&Bound<'py, T>`. Just like `std::sync::Arg`, using `.clone()` and `drop()` will cheaply increment and decrement the reference count of the object (just in this case, the reference counting is implemented by the Python interpreter itself).

Also, drive by comment: Arg should be Arc

MarshalX · 2024-03-10T00:44:19Z

I feel the lack of understanding how #[pyfunction] works. What should I specify as return type. Same with args. I believe that there is a hidden type conversation behind the scene. So I'm confused should I return Bound<> or PyObject... which will not cause type conversation. Should I use PyResult<&str> or return PyResult of Bound PyString. Should I accept args as refs of not. Unfortunately, most code snippets utilize PyResult<()> as the return type :( I will be happy to find answers to these questions in the docs

Speaking of v0.20 I was surprised to gain a huge performance bust by
changing argument type:

-fn _decode_dag_cbor(data: Vec<u8>) -> Result<Ipld> {
+fn _decode_dag_cbor(data: &[u8]) -> Result<Ipld> {

I wish to not make this mistake again

Co-authored-by: Lily Foote <[email protected]>

davidhewitt · 2024-03-10T12:33:41Z

Thanks, I've added a new section specifically talking about the function argument lifetimes to help indicate to use Bound (and why Py is sometimes ok too).

I'd like Vec<u8> to keep to separate issues like #2888, there is definitely discussion to have there.

Icxolu · 2024-03-10T12:49:49Z

guide/src/conversions/traits.md

@@ -484,7 +484,7 @@ If the input is neither a string nor an integer, the error message will be:
 - `pyo3(from_py_with = "...")`
    - apply a custom function to convert the field from Python the desired Rust type.
    - the argument must be the name of the function as a string.
-    - the function signature must be `fn(&PyAny) -> PyResult<T>` where `T` is the Rust type of the argument.
+    - the function signature must be `fn(Bound<PyAny>) -> PyResult<T>` where `T` is the Rust type of the argument.


This can also take a &Bound<PyAny> I believe

I think it is actually just &Bound<PyAny> for now.

Icxolu · 2024-03-10T12:53:48Z

guide/src/memory.md

If we want to keep this section referencing the gil-refs for now, we probably should backport the the examples again, otherwise this does not make a lot of sense

Good idea 👍

guide/src/performance.md

src/lib.rs

guide/src/types.md

Co-authored-by: Icxolu <[email protected]>

guide/src/python-from-rust.md

Co-authored-by: Adam Reichold <[email protected]>

Icxolu

Looks good 🚀 ! There is still calling-existing-code.md to rework, but I think it's fine to merge this as is for the beta and then finish the docs towards final release.

guide/src/async-await.md

Co-authored-by: Adam Reichold <[email protected]>

davidhewitt · 2024-03-10T15:38:13Z

Thanks everyone for the reviews! Definitely there's more the docs can have improved, though I think this PR really did shift the bulk of them onwards and upwards 💹

davidhewitt mentioned this pull request Mar 6, 2024

New Bound API implementation tracking issue #3684

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wip bound docs

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continue to move and tidy up

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update URL

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davidhewitt changed the title ~~docs: WIP update for bound~~ docs: major rewrite for Bound API Mar 10, 2024

update remainder of the guide to Bound API

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release: 0.21.0-beta.0 #3944

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docs: major rewrite for Bound API #3906

docs: major rewrite for Bound API #3906

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	* It provides global APIs for the Python interpreter, such as [`py.eval()`][eval] and [`py.import()`][import].
	* It provides global APIs for the Python interpreter, such as [`py.eval_bound()`][eval] and [`py.import_bound()`][import].


		## The Python GIL, mutability, and Rust types
		These smart pointers have different numbers of lifetime parameters, which defines how they behave. `Py<T>` has no lifetime parameters, `Bound<'py, T>` has a lifetime parameter `'py`, and `Borrowed<'a, 'py, T>` has two lifetime parameters `'a` and `'py`.


		By having the binding to the `'py` lifetime, `Bound<'py, T>` can offer the complete PyO3 API at maximum efficiency. This means that in almost all cases where `Py<T>` is not necessary for lifetime reasons, `Bound<'py, T>` should be used.

		`Bound<'py, T>` engages in Python reference counting. This means that `Bound<'py, T>` owns a Python object. Rust code which just wants to borrow a Python object should use a shared reference `&Bound<'py, T>`. Just like `std::sync::Arg`, using `.clone()` and `drop()` will cheaply implement and decrement the reference count of the object (just in this case, the reference counting is implemented by the Python interpreter itself).

docs: major rewrite for Bound API #3906

docs: major rewrite for Bound API #3906

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davidhewitt commented Feb 26, 2024

codspeed-hq bot commented Mar 8, 2024 • edited Loading

Merging #3906 will not alter performance

🎉 Hooray! pytest-codspeed just leveled up to 2.2.0!

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🎉 Hooray! `pytest-codspeed` just leveled up to 2.2.0!

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