# Create a New Perceptor

Perceptors use the SDK and CLI workflow.

To access a template for a perceptor, type `composabl perceptor new` into the CLI. AMESA will then generate a perceptor template that you can populate with your information.

In this simple perceptor example we calculate the perceptor outputs that will be added as new sensor variables and we create a list of perceptors that comprise the perception layer.

```python
python
class DeltaCounter():
    def __init__(self):
        self.key = "state1"
        self.previous_value = None

    def compute(self, sensors):
        if self.previous_value is None:
            self.previous_value = sensors[self.key]
            return {"delta_counter": 0, "state2": 0}

        delta = sensors ["state1"] - self.previous_value
        self.previous_value = sensors["state1"]
        return {"delta_counter": delta, "state2": 0}

    def filtered_sensor_space(self, sensors):
        return ["state1"]

delta_counter = Perceptor(["delta_counter", "state2"], DeltaCounter, "the change in the counter from the last two steps")

```


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