Understand ZenML artifacts

Step outputs in ZenML are stored in the artifact store. This enables caching, lineage and auditability. Using type annotations helps with transparency, passing data between steps, and serializing/des

For best results, use type annotations for your outputs. This is good coding practice for transparency, helps ZenML handle passing data between steps, and also enables ZenML to serialize and deserialize (referred to as 'materialize' in ZenML) the data.

@step
def load_data(parameter: int) -> Dict[str, Any]:

    # do something with the parameter here

    training_data = [[1, 2], [3, 4], [5, 6]]
    labels = [0, 1, 0]
    return {'features': training_data, 'labels': labels}

@step
def train_model(data: Dict[str, Any]) -> None:
    total_features = sum(map(sum, data['features']))
    total_labels = sum(data['labels'])
    
    # Train some model here
    
    print(f"Trained model using {len(data['features'])} data points. "
          f"Feature sum is {total_features}, label sum is {total_labels}")


@pipeline  
def simple_ml_pipeline(parameter: int):
    dataset = load_data(parameter=parameter)  # Get the output 
    train_model(dataset)  # Pipe the previous step output into the downstream step

In this code, we define two steps: load_data and train_model. The load_data step takes an integer parameter and returns a dictionary containing training data and labels. The train_model step receives the dictionary from load_data, extracts the features and labels, and trains a model (not shown here).

Finally, we define a pipeline simple_ml_pipeline that chains the load_data and train_model steps together. The output from load_data is passed as input to train_model, demonstrating how data flows between steps in a ZenML pipeline.