Dates

Introduction

In this assignment you will practice:

• writing functions,
• documenting functions,
• doing basic operations with values and variables, and
• dealing with date-related data.

Problem Description

You want to get information about dates and days that require some calculation

Solution Description

Write a module called dates (which you should save in a file called dates.py) with the following functions. For each function, be sure to the function design recipe in Practical Programming: An Introduction to Computer Science using Python 3.6, Chapter 3 and summarized in our slides on Python functions, including the type contract using type hints and a docstring.

days_since_epoch

Inspired by Exercise 1 in Think Python, 2e, Chapter 5

The time funciton of the time module in Python’s standard library returns the number of seconds since the “epoch”, which is arbitrarily defined as midnight, 1 January 1970. The return value of the time function is a float that includes a fractional part if your computer’s internal clock keeps time in increments smaller than one second. For example:

>>> import time
>>> time.time()
1539877438.7275572

Write a function named days_since_epoch that takes no parameters and returns an int value denoting the number of days since the epoch.

Hints

• You’ll need to calculate how many seconds are in a day.
• You may need to use a type conversion function to ensure that your function returns an int.

Python REPL Examples

>>> days_since_epoch()
17822

weeks_elapsed

Inspired by Chapter 3, Exercise 8 in Practical Programming: An Introduction to Computer Science using Python 3.6

Write a function named weeks_elapsed that takes an int parameter indicating a number of days of elapsed time and returns an int value indicating the number of full weeks that would elapse in that number of days.

Python REPL Examples

>>> weeks_elapsed(16)
2

weekday_from

You use numbers to indicate the day of the week, 0 to represent Monday, 1 to represent Tuesday, and so on.

Write a function named weekday_from that takes two int parameters:

• today – the current day, and
• days – a number of days from today

and returns an int indicating the weekday on which the day days from today will fall. For example, if today is day 2, then 5 days from today will be day 0, 8 days from today will be day 3, and 15 days from today will be day 3.

• Hint: use Python’s modulus operator.

Python REPL Examples

>>> weekday_from(2, 15)
3

is_leapyear

Leap years are years with one additional day (e,g., 29 February) in order to re-calibrate calendar years to align with astronomical years. In the modern Gregorian calendar leap years are defined as follows:

Every year that is exactly divisible by four is a leap year, except for years that are exactly divisible by 100, but these centurial years are leap years if they are exactly divisible by 400. For example, the years 1700, 1800, and 1900 were not leap years, but the years 1600 and 2000 were. – Introduction to Calendars, US Naval Observatory

Write a function is_leapyear that takes a single int parameter named year and returns True if the year is a leap year, False otherwise.

Python REPL Examples

>>> is_leapyear(2016)
True
>>> is_leapyear(2017)
False

doctest

Use doctest to test your module using Python REPL examples similar to the ones provided for each function above. You may wish to include these test cases in your function docstrings, as well as others that you come up with on your own to test edge cases. Remember that you can run docstring on your module like this: