Implementation:PrefectHQ Prefect Save CSV Task

Metadata
Sources	Prefect
Domains	ETL, Data_Engineering
Last Updated	2026-02-09 00:00 GMT

Overview

Concrete task for persisting a pandas DataFrame to CSV provided by the Prefect ETL example.

Description

The save_csv task writes a DataFrame to disk as CSV and logs a preview of the saved data. It uses pandas' to_csv with index=False and prints a summary.

Code Reference

• Repository: https://github.com/PrefectHQ/prefect
• File: examples/run_api_sourced_etl.py (L113-117)
• Signature:

@task
def save_csv(df: pd.DataFrame, path: Path) -> None:
    """Persist DataFrame to disk then log a preview."""
    df.to_csv(path, index=False)
    print(f"Saved {len(df)} rows → {path}\n\nPreview:\n{df.head()}\n")

• Import: from prefect import task; import pandas as pd; from pathlib import Path

I/O Contract

Inputs

• df (pd.DataFrame, required) -- the transformed DataFrame to persist
• path (Path, required) -- output file path

Outputs

• None (side effect: CSV file written to disk, preview logged)

Usage Example

from pathlib import Path
from prefect import flow, task
import pandas as pd

@task
def save_csv(df: pd.DataFrame, path: Path) -> None:
    df.to_csv(path, index=False)
    print(f"Saved {len(df)} rows to {path}")

@flow(name="devto_etl", log_prints=True)
def etl():
    df = to_dataframe(raw_pages)
    save_csv(df, Path("devto_articles.csv"))

Related Pages

• Principle:PrefectHQ_Prefect_CSV_Data_Loading