Set column names when stacking pandas DataFrame

Question

When stacking a pandas DataFrame, a Series is returned. Normally after I stack a DataFrame, I convert it back into a DataFrame

Answer 1

A pipe-ing friendly alternative to chrisb's answer:

df.stack().rename_axis(['id', 'date', 'var_name']).rename('value').reset_index()

And if explicit is better than implicit:

(
    df
    .stack()
    .rename_axis(index={'id': 'id', 'date': 'date', None: 'var_name'})
    .rename('value')
    .reset_index()
)

When using the dict mapper, you can skip the names which should stay the same:

df.stack().rename_axis(index={None: 'var_name'}).rename('value').reset_index()