Introductory Exercises

Overview

Teaching: 0 min
Exercises: 20 min

Questions

• What questions do you have from yesterday?

Objectives

• Download the data needed for the next part of the lesson.

• Review ideas from yesterday, including functions, conditionals, and loops.

As we get started, please complete the following two exercises.

Getting the Data

The data we will be using is taken from the gapminder dataset. Create a directory called python-novice-gapminder, and download the zip file python-novice-gapminder-data.zip into it. Then unzip the file (it should create a data folder. Then start a Jupyter notebook from inside this directory.

Review From Yesterday

In your notebook, write a function that determines whether a year between 1901 and 2000 is a leap year, where it prints a message like “1904 is a leap year” or “1905 is not a leap year” as output. Use this function to evaluate the years 1928, 1950, 1959, 1972 and 1990.

Hint: the percent symbol ‘%’ is the modular operator in Python. So:

print('8 mod 4 equals', 8 % 4)
print('10 mod 4 equals', 10 % 4)

8 mod 4 equals 0
10 mod 4 equals 2

If you’re not sure where to start, see the partial answers below:

Suggested Approach

First, try to determine how to use the mod operator % to determine if a year is divisible by 4 (and thus a leap year or not).

Then, create a conditional statement to use this information, and put it into a function.

Finally, create a list of the years given in the exercise. Use a for loop and your function to evaluate these years.

Modular Arthimetic

If a year in the range specified is divisible by four, it is a leap year.
If a number is divisible by 4, then the arithmetic expression “number mod four” (or num % 4 in Python) will equal zero.

Conditional Statement

Fill in the blanks:

year = 1904
if year % 4 == _____:
    print(year, _______________)
______: 
    print(year, "is not a leap year.")

Function

Fill in the blanks:

def leap_year(year):
	_________

Loop

Fill in the blanks:

year_list = [1928, 1950, 1959, 1972, 1990]
for year in ______:
    ________(year)

Complete Solution

def leap_year(year):
    if year % 4 == 0:
        print(year, "is a leap year")
    else:
        print(year, "is not a leap year.")

year_list = [1928, 1950, 1959, 1972, 1990]
for year in year_list:
    leap_year(year)

If you have time:

1. Expand your function so that it correctly categorizes any year from 0 onwards

2. Instead of printing whether a year is a leap year or not, save the results to a python dictionary, where there are two keys (“leap” and “not-leap”) and the values are a list of years.

Key Points

• Today’s topics will build on skills we used yesterday.