Utilizing Python Loops

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: "))

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.

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.

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
...
$