Exercises

Exercise 1:

Write a function called mul_time that takes a Time object and a number and returns a new Time object that contains the product of the original Time and the number.

Then use mul_time to write a function that takes a Time object that represents the finishing time in a race, and a number that represents the distance, and returns a Time object that represents the average pace (time per mile).

Exercise 2:

Write a class definition for a Date object that has attributes day, month and year. Write a function called increment_date that takes a Date object, date and an integer, n, and returns a new Date object that represents the day n days after date.

"Thirty days hath September..." Challenge: does your function deal with leap years correctly?

Exercise 3:

The datetime module provides date and time objects that are similar to the Date and Time objects in this chapter, but they provide a rich set of methods and operators. Read the documentation of both objects.

• Use the datetime module to write a program that gets the current date and prints the day of the week.

• Write a program that takes a birthday as input and prints the user's age and the number of days, hours, minutes and seconds until their next birthday.

Exercise 4:

This exercise is a cautionary tale about one of the most common, and difficult to find, errors in Python.

• Write a definition for a class named Kangaroo with the following methods:

  • An __init__ method that initialises an attribute named pouch_contents to an empty list.

  • A method named put_in_pouch that takes an object of any type and adds it to pouch_contents.

  • A __str__ method that returns a string representation of the Kangaroo object and the contents of the pouch.

  Test your code by creating two Kangaroo objects, assigning them to variables named kanga} and roo, and then adding roo to the contents of kanga's pouch.

• Download BadKangaroo.py. It contains a solution to the previous problem with one big, nasty bug. Find and fix the bug.

If you get stuck, you can download GoodKangaroo.py, which explains the problem and demonstrates a solution.