Implementation:PrefectHQ Prefect Materialize Decorator

Metadata
Source	Repo: Prefect
Domains	Data_Engineering, Orchestration
Last Updated	2026-02-09 00:00 GMT

Overview

Concrete decorator for creating tracked, versioned data asset materializations provided by the Prefect library.

Description

The @materialize decorator from prefect.assets wraps a function to track its output as a named data asset. It takes an Asset instance as argument and automatically:

• Tracks the function's return value as that asset
• Infers dependencies from function parameters matching upstream asset names
• Enables caching and versioning
• Records lineage in the Prefect UI

Code Reference

• Repository: https://github.com/PrefectHQ/prefect
• File: src/prefect/assets/materialize.py (L17) for the decorator, examples/atproto_dashboard_with_prefect_assets.py (L73-152) for usage
• Signature:

def materialize(asset: Asset) -> Callable:
    """Decorator that marks a function as materializing a specific asset.

    Args:
        asset: The Asset instance this function materializes.
    """

• Import: from prefect.assets import Asset, materialize

I/O Contract

• Inputs: asset (Asset, required -- the asset this function produces)
• The decorated function's parameters define upstream dependencies
• Outputs: The decorated function's return value, tracked as the specified asset

Usage Example

from prefect.assets import Asset, materialize
from prefect import flow

raw_data_asset = Asset(key="pipeline://raw_data")
processed_data_asset = Asset(key="pipeline://processed_data")

@materialize(raw_data_asset)
def fetch_raw_data() -> dict:
    return {"items": ["item1", "item2"], "fetched_at": "2026-01-01", "count": 2}

@materialize(processed_data_asset)
def process_data(raw_data: dict) -> dict:
    # Prefect infers dependency on raw_data_asset from parameter name
    return {"items": [item.upper() for item in raw_data["items"]],
            "processed_at": "2026-01-01"}

@flow(name="asset-pipeline-demo", log_prints=True)
def run_pipeline():
    raw = fetch_raw_data()
    processed = process_data(raw)
    return processed

Related Pages

Principle:PrefectHQ_Prefect_Asset_Materialization