test_0_width_df.py

import polars as pl


def test_0_width_df() -> None:
    df = pl.DataFrame(height=5)

    assert df.clear().height == 0
    assert df.clone().height == 5
    assert df.cast({}).height == 5
    assert df.equals(df)
    assert not df.equals(pl.DataFrame())
    assert df.estimated_size() == 0
    assert df.join(df, how="cross").height == 25

    out = df.hash_rows()
    assert out.value_counts()["count"].item() == 5

    assert pl.concat(2 * [pl.DataFrame(height=5)]).height == 10