`#[pyclass]` can be used with the following parameters: | Parameter | Description | | :- | :- | | `crate = "some::path"` | Path to import the `pyo3` crate, if it's not accessible at `::pyo3`. | | `dict` | Gives instances of this class an empty `__dict__` to store custom attributes. | | `extends = BaseType` | Use a custom baseclass. Defaults to [`PyAny`][params-1] | | `freelist = N` | Implements a [free list][params-2] of size N. This can improve performance for types that are often created and deleted in quick succession. Profile your code to see whether `freelist` is right for you. | | `frozen` | Declares that your pyclass is immutable. It removes the borrow checker overhead when retrieving a shared reference to the Rust struct, but disables the ability to get a mutable reference. | | `get_all` | Generates getters for all fields of the pyclass. | | `mapping` | Inform PyO3 that this class is a [`Mapping`][params-mapping], and so leave its implementation of sequence C-API slots empty. | | `module = "module_name"` | Python code will see the class as being defined in this module. Defaults to `builtins`. | | `name = "python_name"` | Sets the name that Python sees this class as. Defaults to the name of the Rust struct. | | `sequence` | Inform PyO3 that this class is a [`Sequence`][params-sequence], and so leave its C-API mapping length slot empty. | | `set_all` | Generates setters for all fields of the pyclass. | | `subclass` | Allows other Python classes and `#[pyclass]` to inherit from this class. Enums cannot be subclassed. | | `text_signature = "(arg1, arg2, ...)"` | Sets the text signature for the Python class' `__new__` method. | | `unsendable` | Required if your struct is not [`Send`][params-3]. Rather than using `unsendable`, consider implementing your struct in a threadsafe way by e.g. substituting [`Rc`][params-4] with [`Arc`][params-5]. By using `unsendable`, your class will panic when accessed by another thread.| | `weakref` | Allows this class to be [weakly referenceable][params-6]. | All of these parameters can either be passed directly on the `#[pyclass(...)]` annotation, or as one or more accompanying `#[pyo3(...)]` annotations, e.g.: ```rust,ignore // Argument supplied directly to the `#[pyclass]` annotation. #[pyclass(name = "SomeName", subclass)] struct MyClass {} // Argument supplied as a separate annotation. #[pyclass] #[pyo3(name = "SomeName", subclass)] struct MyClass {} ``` [params-1]: https://docs.rs/pyo3/latest/pyo3/struct.PyAny.html [params-2]: https://en.wikipedia.org/wiki/Free_list [params-3]: https://doc.rust-lang.org/std/marker/trait.Send.html [params-4]: https://doc.rust-lang.org/std/rc/struct.Rc.html [params-5]: https://doc.rust-lang.org/std/sync/struct.Arc.html [params-6]: https://docs.python.org/3/library/weakref.html [params-mapping]: https://pyo3.rs/latest/class/protocols.html#mapping--sequence-types [params-sequence]: https://pyo3.rs/latest/class/protocols.html#mapping--sequence-types