| Exercises |
| ========= |
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| It is often useful to work through some examples in order to understand how a module works; on this page, there are several exercises of varying difficulty that you can use to learn how to use ``dateutil``. |
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| If you are interested in helping improve the documentation of ``dateutil``, it is recommended that you attempt to complete these exercises with no resources *other than dateutil's documentation*. If you find that the documentation is not clear enough to allow you to complete these exercises, open an issue on the `dateutil issue tracker <https://github.com/dateutil/dateutil/issues>`_ to let the developers know what part of the documentation needs improvement. |
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| .. contents:: Table of Contents |
| :backlinks: top |
| :local: |
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| .. _mlk-day-exercise: |
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| Martin Luther King Day |
| -------------------------------- |
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| `Martin Luther King, Jr Day <https://en.wikipedia.org/wiki/Martin_Luther_King_Jr._Day>`_ is a US holiday that occurs every year on the third Monday in January? |
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| How would you generate a `recurrence rule <../rrule.html>`_ that generates Martin Luther King Day, starting from its first observance in 1986? |
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| **Test Script** |
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| To solve this exercise, copy-paste this script into a document, change anything between the ``--- YOUR CODE ---`` comment blocks. |
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| .. raw:: html |
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| <details> |
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| .. code-block:: python3 |
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| # ------- YOUR CODE -------------# |
| from dateutil import rrule |
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| MLK_DAY = <<YOUR CODE HERE>> |
| |
| # -------------------------------# |
| |
| from datetime import datetime |
| MLK_TEST_CASES = [ |
| ((datetime(1970, 1, 1), datetime(1980, 1, 1)), |
| []), |
| ((datetime(1980, 1, 1), datetime(1989, 1, 1)), |
| [datetime(1986, 1, 20), |
| datetime(1987, 1, 19), |
| datetime(1988, 1, 18)]), |
| ((datetime(2017, 2, 1), datetime(2022, 2, 1)), |
| [datetime(2018, 1, 15, 0, 0), |
| datetime(2019, 1, 21, 0, 0), |
| datetime(2020, 1, 20, 0, 0), |
| datetime(2021, 1, 18, 0, 0), |
| datetime(2022, 1, 17, 0, 0)] |
| ), |
| ] |
| |
| def test_mlk_day(): |
| for (between_args, expected) in MLK_TEST_CASES: |
| assert MLK_DAY.between(*between_args) == expected |
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| if __name__ == "__main__": |
| test_mlk_day() |
| print('Success!') |
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| .. raw:: html |
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| </details> |
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| A solution to this problem is provided :doc:`here <solutions/mlk-day-rrule>`. |
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| Next Monday meeting |
| ------------------- |
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| A team has a meeting at 10 AM every Monday and wants a function that tells them, given a ``datetime.datetime`` object, what is the date and time of the *next* Monday meeting? This is probably best accomplished using a `relativedelta <../relativedelta.html>`_. |
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| **Test Script** |
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| To solve this exercise, copy-paste this script into a document, change anything between the ``--- YOUR CODE ---`` comment blocks. |
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| .. raw:: html |
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| <details> |
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| .. code-block:: python3 |
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| # --------- YOUR CODE -------------- # |
| from dateutil import relativedelta |
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| def next_monday(dt): |
| <<YOUR CODE HERE>> |
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| # ---------------------------------- # |
| |
| from datetime import datetime |
| from dateutil import tz |
| |
| NEXT_MONDAY_CASES = [ |
| (datetime(2018, 4, 11, 14, 30, 15, 123456), |
| datetime(2018, 4, 16, 10, 0)), |
| (datetime(2018, 4, 16, 10, 0), |
| datetime(2018, 4, 16, 10, 0)), |
| (datetime(2018, 4, 16, 10, 30), |
| datetime(2018, 4, 23, 10, 0)), |
| (datetime(2018, 4, 14, 9, 30, tzinfo=tz.gettz('America/New_York')), |
| datetime(2018, 4, 16, 10, 0, tzinfo=tz.gettz('America/New_York'))), |
| ] |
| |
| def test_next_monday_1(): |
| for dt_in, dt_out in NEXT_MONDAY_CASES: |
| assert next_monday(dt_in) == dt_out |
| |
| if __name__ == "__main__": |
| test_next_monday_1() |
| print('Success!') |
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| .. raw:: html |
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| </details> |
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| Parsing a local tzname |
| ---------------------- |
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| Three-character time zone abbreviations are *not* unique in that they do not explicitly map to a time zone. A list of time zone abbreviations in use can be found `here <https://www.timeanddate.com/time/zones/>`_. This means that parsing a datetime string such as ``'2018-01-01 12:30:30 CST'`` is ambiguous without context. Using `dateutil.parser <../parser.html>`_ and `dateutil.tz <../tz.html>`_, it is possible to provide a context such that these local names are converted to proper time zones. |
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| Problem 1 |
| ********* |
| Given the context that you will only be parsing dates coming from the continental United States, India and Japan, write a function that parses a datetime string and returns a timezone-aware ``datetime`` with an IANA-style timezone attached. |
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| Note: For the purposes of the experiment, you may ignore the portions of the United States like Arizona and parts of Indiana that do not observe daylight saving time. |
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| **Test Script** |
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| To solve this exercise, copy-paste this script into a document, change anything between the ``--- YOUR CODE ---`` comment blocks. |
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| .. raw:: html |
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| <details> |
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| .. code-block:: python3 |
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| # --------- YOUR CODE -------------- # |
| from dateutil.parser import parse |
| from dateutil import tz |
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| def parse_func_us_jp_ind(): |
| <<YOUR CODE HERE>> |
| |
| # ---------------------------------- # |
| |
| from dateutil import tz |
| from datetime import datetime |
| |
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| PARSE_TZ_TEST_DATETIMES = [ |
| datetime(2018, 1, 1, 12, 0), |
| datetime(2018, 3, 20, 2, 0), |
| datetime(2018, 5, 12, 3, 30), |
| datetime(2014, 9, 1, 23) |
| ] |
| |
| PARSE_TZ_TEST_ZONES = [ |
| tz.gettz('America/New_York'), |
| tz.gettz('America/Chicago'), |
| tz.gettz('America/Denver'), |
| tz.gettz('America/Los_Angeles'), |
| tz.gettz('Asia/Kolkata'), |
| tz.gettz('Asia/Tokyo'), |
| ] |
| |
| def test_parse(): |
| for tzi in PARSE_TZ_TEST_ZONES: |
| for dt in PARSE_TZ_TEST_DATETIMES: |
| dt_exp = dt.replace(tzinfo=tzi) |
| dtstr = dt_exp.strftime('%Y-%m-%d %H:%M:%S %Z') |
| |
| dt_act = parse_func_us_jp_ind(dtstr) |
| assert dt_act == dt_exp |
| assert dt_act.tzinfo is dt_exp.tzinfo |
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| if __name__ == "__main__": |
| test_parse() |
| print('Success!') |
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| .. raw:: html |
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| </details> |
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| Problem 2 |
| ********* |
| Given the context that you will *only* be passed dates from India or Ireland, write a function that correctly parses all *unambiguous* time zone strings to aware datetimes localized to the correct IANA zone, and for *ambiguous* time zone strings default to India. |
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| **Test Script** |
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| To solve this exercise, copy-paste this script into a document, change anything between the ``--- YOUR CODE ---`` comment blocks. |
| |
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| .. raw:: html |
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| <details> |
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| .. code-block:: python3 |
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| # --------- YOUR CODE -------------- # |
| from dateutil.parser import parse |
| from dateutil import tz |
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| def parse_func_ind_ire(): |
| <<YOUR CODE HERE>> |
| |
| # ---------------------------------- # |
| ISRAEL = tz.gettz('Asia/Jerusalem') |
| INDIA = tz.gettz('Asia/Kolkata') |
| PARSE_IXT_TEST_CASE = [ |
| ('2018-02-03 12:00 IST+02:00', datetime(2018, 2, 3, 12, tzinfo=ISRAEL)), |
| ('2018-06-14 12:00 IDT+03:00', datetime(2018, 6, 14, 12, tzinfo=ISRAEL)), |
| ('2018-06-14 12:00 IST', datetime(2018, 6, 14, 12, tzinfo=INDIA)), |
| ('2018-06-14 12:00 IST+05:30', datetime(2018, 6, 14, 12, tzinfo=INDIA)), |
| ('2018-02-03 12:00 IST', datetime(2018, 2, 3, 12, tzinfo=INDIA)), |
| ] |
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| def test_parse_ixt(): |
| for dtstr, dt_exp in PARSE_IXT_TEST_CASE: |
| dt_act = parse_func_ind_ire(dtstr) |
| assert dt_act == dt_exp, (dt_act, dt_exp) |
| assert dt_act.tzinfo is dt_exp.tzinfo, (dt_act, dt_exp) |
| |
| if __name__ == "__main__": |
| test_parse_ixt() |
| print('Success!') |
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| .. raw:: html |
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| </details> |
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