Repository: Genesis-Embodied-AI/Genesis
File: genesis/sensors/sensor_manager.py (Python)

Code before:

class SensorManager:
    SENSOR_TYPES_MAP: dict[Type["SensorOptions"], Type["Sensor"]] = {}

    def __init__(self, sim):
        self._sim = sim
        self._sensors: list["Sensor"] = []
        self._sensors_metadata: dict[Type["Sensor"], dict[str, Any]] = {}
        self._ground_truth_cache: dict[Type[torch.dtype], torch.Tensor] = {}
        self._cache: dict[Type[torch.dtype], TensorRingBuffer] = {}
        self._first_sensor_per_type: dict[Type["Sensor"], "Sensor"] = {}

    def create_sensor(self, sensor_options: "SensorOptions"):
        sensor_cls = SensorManager.SENSOR_TYPES_MAP[type(sensor_options)]
        sensor = sensor_cls(sensor_options, len(self._sensors), self)
        self._sensors.append(sensor)
        return sensor

    def build(self):
        max_cache_buf_len = 0
        cache_size_per_dtype = {}
        for sensor in self._sensors:
            if sensor.__class__ not in self._sensors_metadata:
                self._sensors_metadata[sensor.__class__] = {}
            if sensor.__class__ not in self._first_sensor_per_type:
                self._first_sensor_per_type[sensor.__class__] = sensor

            sensor.build()

            if sensor._get_cache_dtype() not in cache_size_per_dtype:
                cache_size_per_dtype[sensor._get_cache_dtype()] = 0

            sensor._cache_idx = cache_size_per_dtype[sensor._get_cache_dtype()]
            cache_size_per_dtype[sensor._get_cache_dtype()] += sensor._cache_size

            max_cache_buf_len = max(max_cache_buf_len, sensor._read_delay_steps + 1)

        for dtype in cache_size_per_dtype.keys():
            cache_shape = (self._sim._B, cache_size_per_dtype[dtype])
            self._ground_truth_cache[dtype] = torch.zeros(cache_shape, dtype=dtype)
            self._cache[dtype] = TensorRingBuffer(max_cache_buf_len, cache_shape, dtype=dtype)

    def step(self):
        for sensor in self._first_sensor_per_type.values():
            sensor._update_shared_ground_truth_cache()
            sensor._update_shared_cache()

    @property
    def sensors(self):
        return [sensor for sensor_list in self._sensors_by_type.values() for sensor in sensor_list]


Review comment (suggestion):
Just use `setdefault`:
```python
self._sensors_metadata.setdefault(sensor_type, {})
self._first_sensor_per_type.setdefault(sensor_type, sensor)
```

Code after:
    from .base_sensor import Sensor


class SensorManager:
    SENSOR_TYPES_MAP: dict[Type["SensorOptions"], Type["Sensor"]] = {}

    def __init__(self, sim):
        self._sim = sim
        self._sensors_by_type: dict[Type["Sensor"], list["Sensor"]] = {}
        self._sensors_metadata: dict[Type["Sensor"], dict[str, Any]] = {}
        self._ground_truth_cache: dict[Type[torch.dtype], torch.Tensor] = {}
        self._cache: dict[Type[torch.dtype], TensorRingBuffer] = {}
        self._cache_slices_by_type: dict[Type["Sensor"], slice] = {}

        self._last_ground_truth_cache_cloned_step: dict[Type[torch.dtype], int] = {}
        self._cloned_ground_truth_cache: dict[Type[torch.dtype], torch.Tensor] = {}

    def create_sensor(self, sensor_options: "SensorOptions"):
        sensor_cls = SensorManager.SENSOR_TYPES_MAP[type(sensor_options)]
        self._sensors_by_type.setdefault(sensor_cls, [])
        sensor = sensor_cls(sensor_options, len(self._sensors_by_type[sensor_cls]), self)
        self._sensors_by_type[sensor_cls].append(sensor)
        return sensor

    def build(self):
        max_cache_buf_len = 0
        cache_size_per_dtype = {}
        for sensor_cls, sensors in self._sensors_by_type.items():
            self._sensors_metadata[sensor_cls] = {}
            dtype = sensor_cls._get_cache_dtype()
            cache_size_per_dtype.setdefault(dtype, 0)
            cls_cache_start_idx = cache_size_per_dtype[dtype]

            for sensor in sensors:
                return_format = sensor._get_return_format()
                return_shapes = return_format.values() if isinstance(return_format, dict) else (return_format,)

                tensor_size = 0
                for shape in return_shapes:
                    data_size = np.prod(shape)
                    sensor._shape_indices.append((tensor_size, tensor_size + data_size))
                    tensor_size += data_size

                delay_steps_float = sensor._options.read_delay / self._sim.dt
                sensor._read_delay_steps = round(delay_steps_float)
                if not np.isclose(delay_steps_float, sensor._read_delay_steps, atol=1e-6):
                    gs.logger.warn(
                        f"Read delay should be a multiple of the simulation time step. Got {sensor._options.read_delay}"
                        f" and {self._sim.dt}. Actual read delay will be {1/sensor._read_delay_steps}."
                    )