Lazy pivot to wide format

The dashboard team wants a wide month-by-format view of checkouts. Polars supports .pivot() in lazy mode when you specify the output column names in advance, which keeps the whole pipeline optimized end to end.

The LazyFrame monthly_checkouts holds totals in long format with a month, format, and total column, and the list formats holds every format name in the data.

Deze oefening maakt deel uit van de cursus

Scaling and Optimizing Data Pipelines with Polars

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Oefeninstructies

Pivot monthly_checkouts so each format becomes its own column.
Pass the formats list so the lazy pivot knows the output schema in advance.
Sort the resulting DataFrame by month.

Interactieve oefening met praktijkervaring

Probeer deze oefening door deze voorbeeldcode aan te vullen.

result = (
    monthly_checkouts
    # Pivot the format column into separate columns
    .pivot(
        on="____",
        index="month",
        values="total",
        # Pre-declare the output column names so the pivot stays lazy
        on_columns=____,
    )
    .collect()
    # Sort the wide result by month
    .sort("____")
)
print(result)

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