Sharing a mutable reference between Rust and Python
7 days ago
- #Rust
- #PyO3
- #Django
- The article discusses implementing Django's templating language in Rust, focusing on custom template tags.
- Simple tags in Django can be created using the `@register.simple_tag` decorator and used in templates with `{% load %}` and `{% tag %}` syntax.
- Django's templating context behaves like a Python dictionary and can be passed to tags using `takes_context=True`.
- In Rust, the context is implemented as a struct with a `HashMap` and passed as a mutable reference during rendering.
- To interface with Python, the Rust context is wrapped in a `PyContext` class using PyO3, but Rust's ownership model complicates this.
- Using `std::mem::take` and `std::mem::replace` allows for transferring ownership of the context between Rust and Python.
- An `Arc` (atomic reference count) is used to manage shared ownership of the context, with `Arc::try_unwrap` to reclaim ownership.
- For cases where Python retains references, the context is cloned using a `clone_ref` method to handle Python's reference counting.
- To enable mutation of the context from Python, a `Mutex` is used along with PyO3's `MutexExt` to avoid deadlocks.
- The article concludes that PyO3 and Rust's memory management tools like `Arc` and `Mutex` effectively bridge Rust's ownership model with Python's dynamic nature.