polars.business_day_count

polars.business_day_count(

start: date | IntoExprColumn,

end: date | IntoExprColumn,

week_mask: Iterable[bool] = (True, True, True, True, True, False, False),

holidays: Iterable[date] = (),

) → Expr

Count the number of business days between start and end (not including end).

Parameters:

start

Start dates.

end

End dates.

week_mask

Which days of the week to count. The default is Monday to Friday. If you wanted to count only Monday to Thursday, you would pass (True, True, True, True, False, False, False).

holidays

Holidays to exclude from the count. The Python package python-holidays may come in handy here. You can install it with pip install holidays, and then, to get all Dutch holidays for years 2020-2024:

import holidays

my_holidays = holidays.country_holidays("NL", years=range(2020, 2025))

and pass holidays=my_holidays when you call business_day_count.

Returns:

Expr

Examples

>>> from datetime import date
>>> df = pl.DataFrame(
...     {
...         "start": [date(2020, 1, 1), date(2020, 1, 2)],
...         "end": [date(2020, 1, 2), date(2020, 1, 10)],
...     }
... )
>>> df.with_columns(
...     business_day_count=pl.business_day_count("start", "end"),
... )
shape: (2, 3)
┌────────────┬────────────┬────────────────────┐
│ start      ┆ end        ┆ business_day_count │
│ ---        ┆ ---        ┆ ---                │
│ date       ┆ date       ┆ i32                │
╞════════════╪════════════╪════════════════════╡
│ 2020-01-01 ┆ 2020-01-02 ┆ 1                  │
│ 2020-01-02 ┆ 2020-01-10 ┆ 6                  │
└────────────┴────────────┴────────────────────┘

Note how the business day count is 6 (as opposed a regular day count of 8) due to the weekend (2020-01-04 - 2020-01-05) not being counted.

You can pass a custom weekend - for example, if you only take Sunday off:

>>> week_mask = (True, True, True, True, True, True, False)
>>> df.with_columns(
...     business_day_count=pl.business_day_count("start", "end", week_mask),
... )
shape: (2, 3)
┌────────────┬────────────┬────────────────────┐
│ start      ┆ end        ┆ business_day_count │
│ ---        ┆ ---        ┆ ---                │
│ date       ┆ date       ┆ i32                │
╞════════════╪════════════╪════════════════════╡
│ 2020-01-01 ┆ 2020-01-02 ┆ 1                  │
│ 2020-01-02 ┆ 2020-01-10 ┆ 7                  │
└────────────┴────────────┴────────────────────┘

You can also pass a list of holidays to exclude from the count:

>>> from datetime import date
>>> holidays = [date(2020, 1, 1), date(2020, 1, 2)]
>>> df.with_columns(
...     business_day_count=pl.business_day_count("start", "end", holidays=holidays)
... )
shape: (2, 3)
┌────────────┬────────────┬────────────────────┐
│ start      ┆ end        ┆ business_day_count │
│ ---        ┆ ---        ┆ ---                │
│ date       ┆ date       ┆ i32                │
╞════════════╪════════════╪════════════════════╡
│ 2020-01-01 ┆ 2020-01-02 ┆ 0                  │
│ 2020-01-02 ┆ 2020-01-10 ┆ 5                  │
└────────────┴────────────┴────────────────────┘