Lib.rs

A wrapper of Gymnasium environments on Python.

GymEnv is a wrapper of Gymnasium based on PyO3. It has been tested on some of classic control and Gymnasium-Robotics environments.

In order to bridge Python and Rust, we need to convert Python objects to Rust objects and vice versa.

Observation

Observation is created in Python and passed to Rust as a Python object. In order to convert Python object to Rust object, this crate provides GymObsFilter trait. This trait has GymObsFilter::filt method which converts Python object to Rust object. The type of the Rust object after conversion corresponds to the type parameter O of the trait and this is also the type of the observation in the environment, i.e., GymEnv::Obs.

There are two built-in implementations of GymObsFilter: ArrayObsFilter and ArrayDictObsFilter. ArrayObsFilter is for environments where observation is an array (e.g., CartPole). Internally, the array is converted to ndarray::ArrayD from Python object. Then, the array is converted to the type parameter O of the filter. Since O must implement From<ndarray::ArrayD> by trait bound, the conversion is done by calling array.into().

ArrayDictObsFilter is for environments where observation is a dictionary of arrays (e.g., FetchPickAndPlace). Internally, the dictionary is converted to Vec<(String, border_py_gym_env:util::Array)> from Python object. Then, Vec<(String, border_py_gym_env:util::Array)> is converted to O by calling into().

Action

Action is created in Policy and passed to Python as a Python object. In order to convert Rust object to Python object, this crate provides GymActFilter trait. This trait has GymActFilter::filt method which converts Rust object of type A, which is the type parameter of the trait, to Python object.

There are two built-in implementations of GymActFilter: DiscreteActFilter and ContinuousActFilter. DiscreteActFilter is for environments where action is discrete (e.g., CartPole). This filter converts A to Vec<i32> and then to Python object. ContinuousActFilter is for environments where action is continuous (e.g., Pendulum). This filter converts A to ArrayD and then to Python object.