Review Exercise

Overview

Questions

• How can we put together all of yesterday’s material?

Objectives

• Apply use of functions, conditionals and loops to solve a problem.

Review From Yesterday - All in One Exercise

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. Essentially, given this list of years:

PYTHON

years = [1928, 1950, 1959, 1972, 1990]

Produce something like:

OUTPUT

1928 is a leap year
1950 is not a leap year.
1959 is not a leap year.
1972 is a leap year
1990 is not a leap year.

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

PYTHON

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

OUTPUT

8 mod 4 equals 0
10 mod 4 equals 2

If you’re not sure where to start, see the fill-in-the-blank version of this exercise below.

Show me the solution

PYTHON

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)

Review From Yesterday - Step by Step Breakdown

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).

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.

Review From Yesterday - Step by Step Breakdown (continued)

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

Conditional Statement

Fill in the blanks:

PYTHON

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

Review From Yesterday - Step by Step Breakdown (continued)

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

Function

Fill in the blanks:

PYTHON

def leap_year(year):
    _________

Review From Yesterday - Step by Step Breakdown (continued)

Finally, use a for loop and your function to evaluate these years.

Loop

Fill in the blanks:

PYTHON

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

Show me the solution

PYTHON

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)

Additonal Challenge

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

• Use skills together.