feat(api): day_of_week.iso_index() method

[kaijennissen]

Description of changes

Added a new isoday_of_week method for timestamps.

Issues closed

Resolves #8989

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[cpcloud]

We have a DayOfWeek class defined in ibis/expr/types/temporal.py.

It's a bit of an oddball API in that it functions like a namespace instead of top level method like everything else.

Naturally, your first development experience with Ibis is extending a slightly weird bit of the codebase 😂.

Perhaps we can add two new methods there?

class DayOfWeek:
    ...

    def iso_index(self): ...
    def iso_full_name(self): ...

for consistency with the surrounding methods?

[cpcloud]

Here's a usage example:

In [8]: t = ibis.read_parquet("/data/avg_duration_over_time.parquet")

In [9]: t.head()
Out[9]:
┏━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━┓
┃ date       ┃ avg_duration_m ┃
┡━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━┩
│ date       │ float64        │
├────────────┼────────────────┤
│ 2024-04-16 │      57.833333 │
│ 2024-04-15 │      42.833333 │
│ 2024-04-14 │      31.500000 │
│ 2024-04-13 │      53.600000 │
│ 2024-04-12 │      47.400000 │
└────────────┴────────────────┘

In [10]: t.select(
    ...:     "date",
    ...:     weekday=t.date.day_of_week.index(),
    ...:     weekday_name=t.date.day_of_week.full_name(),
    ...: )
Out[10]:
┏━━━━━━━━━━━━┳━━━━━━━━━┳━━━━━━━━━━━━━━┓
┃ date       ┃ weekday ┃ weekday_name ┃
┡━━━━━━━━━━━━╇━━━━━━━━━╇━━━━━━━━━━━━━━┩
│ date       │ int16   │ string       │
├────────────┼─────────┼──────────────┤
│ 2024-04-16 │       1 │ Tuesday      │
│ 2024-04-15 │       0 │ Monday       │
│ 2024-04-14 │       6 │ Sunday       │
│ 2024-04-13 │       5 │ Saturday     │
│ 2024-04-12 │       4 │ Friday       │
│ 2024-04-10 │       2 │ Wednesday    │
│ 2024-04-09 │       1 │ Tuesday      │
│ 2024-04-07 │       6 │ Sunday       │
│ 2024-04-06 │       5 │ Saturday     │
│ 2024-04-05 │       4 │ Friday       │
│ …          │       … │ …            │
└────────────┴─────────┴──────────────┘

[cpcloud]

Alternatively, I can take a crack at this one, if you want to handle iso_year()

[kaijennissen]

We have a DayOfWeek class defined in ibis/expr/types/temporal.py.

I missed that.

Alternatively, I can take a crack at this one, if you want to handle iso_year()

I'll give it a try. And iso_yearwith a different PR.

[kaijennissen]

Is it possible that there are currently no tests for .day_of_week.index and .day_of_week.full_name? Was looking to place a test nearby but couldn't find them.

[cpcloud]

@kaijennissen You should be able to find the tests that run across backends in ibis/backends/tests/test_temporal.py:

❯ rg test_day_of_week
ibis/backends/bigquery/tests/unit/test_compiler.py
72:def test_day_of_week(case, dtype, snapshot):

ibis/backends/impala/tests/test_client.py
202:def test_day_of_week(con):

ibis/backends/tests/test_temporal.py
1463:def test_day_of_week_scalar(con, date, expected_index, expected_day):
1484:def test_day_of_week_column(backend, alltypes, df):
1529:def test_day_of_week_column_group_by(

[kaijennissen]

@cpcloud The sqlite tests pass locally. The exasol as well as the impala containers do not work thus I cannot test this locally. I have to investigate this a little deeper. I have no idea why the docs-test fails.

[cpcloud]

@kaijennissen Are you still interested in this feature? If so, would you mind trying it out for your use case and reporting back?

[kaijennissen]

@cpcloud Sorry for the late answer. It works for my use case, thanks.