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Exercises
=========
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``.
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.
.. contents:: Table of Contents
:backlinks: top
:local:
.. _mlk-day-exercise:
Martin Luther King Day
--------------------------------
`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?
How would you generate a `recurrence rule <../rrule.html>`_ that generates Martin Luther King Day, starting from its first observance in 1986?
**Test Script**
To solve this exercise, copy-paste this script into a document, change anything between the ``--- YOUR CODE ---`` comment blocks.
.. raw:: html
<details>
.. code-block:: python3
# ------- YOUR CODE -------------#
from dateutil import rrule
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
if __name__ == "__main__":
test_mlk_day()
print('Success!')
.. raw:: html
</details>
A solution to this problem is provided :doc:`here <solutions/mlk-day-rrule>`.
Next Monday meeting
-------------------
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>`_.
**Test Script**
To solve this exercise, copy-paste this script into a document, change anything between the ``--- YOUR CODE ---`` comment blocks.
.. raw:: html
<details>
.. code-block:: python3
# --------- YOUR CODE -------------- #
from dateutil import relativedelta
def next_monday(dt):
<<YOUR CODE HERE>>
# ---------------------------------- #
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!')
.. raw:: html
</details>
Parsing a local tzname
----------------------
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.
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.
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.
**Test Script**
To solve this exercise, copy-paste this script into a document, change anything between the ``--- YOUR CODE ---`` comment blocks.
.. raw:: html
<details>
.. code-block:: python3
# --------- YOUR CODE -------------- #
from dateutil.parser import parse
from dateutil import tz
def parse_func_us_jp_ind():
<<YOUR CODE HERE>>
# ---------------------------------- #
from dateutil import tz
from datetime import datetime
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
if __name__ == "__main__":
test_parse()
print('Success!')
.. raw:: html
</details>
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.
**Test Script**
To solve this exercise, copy-paste this script into a document, change anything between the ``--- YOUR CODE ---`` comment blocks.
.. raw:: html
<details>
.. code-block:: python3
# --------- YOUR CODE -------------- #
from dateutil.parser import parse
from dateutil import tz
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)),
]
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!')
.. raw:: html
</details>
|
