Utilizing Python Loops

1 hour
  • 4 Learning Objectives

About this Hands-on Lab

One of the great strengths of computer programs is that they can process an incredible amount of information far faster than we could do it manually. To achieve this we need to be able to loop through collections and sequences. In this hands-on lab, we’ll work through the popular interviewing Fizz-Buzz problem by creating a script that will prompt the user for the number of items to process, and then print out either the number, “Fizz”, “Buzz”, or “FizzBuzz” for each number between 1 and the user-provided number.

To feel comfortable completing this lab you’ll want to know how to do the following:

* Utilize `for` loops. Watch “The `for` Loop” video from the [Certified Entry-Level Python Programmer Certification][1] course.
* Nest conditionals and loops. Watch the “Nesting Loops and Conditionals” video from the [Certified Entry-Level Python Programmer Certification][1] course.
* Utilize the `range` type. Watch “Using `range`” video from the [Certified Entry-Level Python Programmer Certification][1] course.

[1]: https://linuxacademy.com/cp/modules/view/id/413

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

Create the fizz-buzz.py Script, Make It Executable with python3.7, and Accept User Input

We’re going to create fizz-buzz.py, placing it in our home directory (~), and we want to make sure that we can run it directly. To keep from being completely tied to the path of our python3.7 binary, we want to make sure that our shebang is set up properly.

Let’s create the file and set the shebang:

~/fizz-buzz.py

#!/usr/bin/env python3.7

# Python implementation here

With the file created, we need to also make sure that it’s executable, and we can do this using chmod:

$ chmod u+x ~/fizz-buzz.py

Next, we’ll prompt the user for a value, convert it to an int, and store it off in a variable.

~/fizz-buzz.py

#!/usr/bin/env python3.7

upper_number = int(input("How many values should we process: "))
Create a Range from 1 to the User’s Provided Number and Loop Through It

To print the number from 1 to the user’s provided number (including that number), we’ll want to utilize the range type and a for loop. Here’s what our loop will look like:

~/fizz-buzz.py

#!/usr/bin/env python3.7

upper_number = int(input("How many values should we process: "))

for number in range(1, upper_number + 1):
    print(number)

If we run it again, and enter 10 at the prompt, we’ll see the numbers 1-10 printed out to the terminal. For now, replace print(number) with pass, and we can move on to write the conditional logic to process each number.

Print “FizzBuzz” if the Value Is a Multiple of Three and Five

Now that we have a number value to use, we can create our conditional. Since we have a case that should trigger if the value is a multiple of three and five, then we’ll want that branch to be before the only multiple of three or only multiple of five branches, because either of those would also be true. Let’s create our if statement and print "FizzBuzz" if the condition is met, then add an else to just print the value otherwise:

~/fizz-buzz.py

#!/usr/bin/env python3.7

upper_number = int(input("How many values should we process: "))

for number in range(1, upper_number + 1):
  if number % 3 == 0 and number % 5 == 0:
      print("FizzBuzz")
  else:
      print(number)

Now we can run the script to make sure that what we’ve written up to this point is working properly:

$ ./fizz-buzz.py
How many values should we process: 20
...
12
13
14
FizzBuzz
16
...
$

15 is replaced by FizzBuzz, because it’s evenly divisible by 3 and 5, and the rest of the numbers print out normally.

Print “Fizz” if the Value Is a Multiple of Three and “Buzz” if It’s a Multiple of Five

To handle the other two cases of the Fizz-Buzz problem, we’ll need to utilize elif statements for each of the individual comparisons that we used in our if statement. Let’s add those now:

~/fizz-buzz.py

#!/usr/bin/env python3.7

upper_number = int(input("How many values should we process: "))

for number in range(1, upper_number + 1):
  if number % 3 == 0 and number % 5 == 0:
      print("FizzBuzz")
  elif number % 3 == 0:
      print("Fizz")
  elif number % 5 == 0:
      print("Buzz")
  else:
      print(number)

Now we can run the script to make sure that what we’ve written up to this point is working properly:

$ ./fizz-buzz.py
How many values should we process: 30
1
2
Fizz
4
Buzz
Fizz
7
8
Fizz
Buzz
11
Fizz
13
14
FizzBuzz
16
17
...
$

Additional Resources

A typical Fizz-Buzz problem goes like this:

Write a program that prints the numbers from 1 - 100. For each multiple of three print "Fizz" instead of the number. For multiples of five print "Buzz" instead of the number. If a number is a multiple of three and five then print "FizzBuzz". Solving this problem requires 2 key components: looping and conditionals.

We're going to write a script that prompts the user for the number of items to process (starting with 1). For each number, we'll print either "Fizz", "Buzz", "FizzBuzz", or the number. The criteria for what to print is:

  • Print "FizzBuzz" if the number is divisible by 3 and 5.
  • Print "Fizz" if the number is divisible by 3.
  • Print "Buzz" if the number is divisible by 5.
  • Otherwise print the number.

Here's how the final script should work:

$ ./fizz-buzz.py
How many values should we process: 20
1
2
Fizz
4
Buzz
Fizz
7
8
Fizz
Buzz
11
Fizz
13
14
FizzBuzz
16
17
Fizz
19
Buzz

Logging In

There are a couple of ways to get in and work with the code. One is to use the credentials provided in the hands-on lab overview page, log in with SSH, and use a text editor in the terminal.

The other is using VS Code in the browser. If you'd like to go this route, then you will need to navigate to the public IP address of the workstation server (provided in the hands-on lab overview page) on port 8080 (example: http://PUBLIC_IP:8080). Your password will be the same password that you'd use to connect over SSH.

What are Hands-on Labs

Hands-on Labs are real environments created by industry experts to help you learn. These environments help you gain knowledge and experience, practice without compromising your system, test without risk, destroy without fear, and let you learn from your mistakes. Hands-on Labs: practice your skills before delivering in the real world.

Get Started
Who’s going to be learning?

How many seats do you need?

  • $499 USD per seat per year
  • Billed Annually
  • Renews in 12 months

Ready to accelerate learning?

For over 25 licenses, a member of our sales team will walk you through a custom tailored solution for your business.


$2,495.00

Checkout
Sign In
Welcome Back!

Psst…this one if you’ve been moved to ACG!