Python Fundamentals 4.3 Function Return Statements

Activity 4.3 Return Statements

Introduction

One important component regarding functions is the ability to give back some information if necessary. Here are a few examples of functions we have used that return some value once the function is finished executing.

int() returns an integer if a valid string argument is provided.
random.randint(n1, n2) returns a number between n1 and n2.
list.count() returns an integer for the number of elements in a list.

It’s not always necessary to return information. For example, print() merely outputs information to the console. There’s no need to return any value.

In programming, functions can use a keyword called return. We call statements involving the return keyword a return statement. Return statements immediately finish executing the function, and return some provided value.

Example

def add(num1, num2):
    return num1 + num2

In the example above, the add function returns the sum of the num1 and num2 parameters. Just like any of the other functions we’ve used, we can assign the return value to a variable.

sum = add(10, 15) # sum = 25

Skills to Practice

Defining functions with parameters
Invoking user defined functions with arguments
Returning values from a function

Instructions

Setup

Create a new repl.
1. Select Python for the language.
2. Name the Repl “4.3 Function Return Statements”.
Click Create repl.

Code

import random

# Function Definitions
# These will be used in the main program below.

def squareNumber(number):
  return number * number

def subtract(number1, number2):
  return number1 - number2

def monthsToYears(months):
  return round(months / 12, 1)

def yearsToMonths(years):
  return years * 12

# Roll a single die
def rollDie(number_of_sides):
  return random.randint(1, number_of_sides)

print("-- Random Utilities Calculator --")
choice = ""

while (choice != "6"):
  print("1) Square a number")
  print("2) Subtract two numbers")
  print("3) Convert months to years")
  print("4) Convert years to months")
  print("5) Roll dice")
  print("6) Exit")

  choice = input("-> ")

  if choice == "1":
    number = float(input("Enter a number: "))
    answer = squareNumber(number)
    print(f"{number} squared is {answer}\n")
  elif choice == "2":
    number = float(input("Enter a number: "))
    number2 = float(input("Enter a number: "))
    answer = subtract(number, number2)
    print(f"{number} minus {number2} equals {answer}\n")
  elif choice == "3":
    number = float(input("Enter a number: "))
    print(f"{number} months equals {monthsToYears(number)} years\n")
  elif choice == "4":
    number = float(input("Enter a number: "))
    print(f"{number} years equals {yearsToMonths(number)} months\n")
  elif choice == "5":
    die1 = rollDie(6)
    die2 = rollDie(6)
    print(f"You rolled a {die1} and a {die2} for a total of {die1 + die2}\n")
  elif choice == "6":
    print("Goodbye")
  else:
    print("Invalid option...")

Debug

-- Random Utilities Calculator --
1) Square a number
2) Subtract two numbers
3) Convert months to years
4) Convert years to months
5) Roll dice
6) Exit
-> 1
Enter a number: 40
40 squared is 1600

1) Square a number
2) Subtract two numbers
3) Convert months to years
4) Convert years to months
5) Roll dice
6) Exit
-> 2
Enter a number: 100
Enter a number: 20.5
100 minus 20.5 equals 79.5

1) Square a number
2) Subtract two numbers
3) Convert months to years
4) Convert years to months
5) Roll dice
6) Exit
-> 3
Enter a number: 24
24 months equals 2 years

1) Square a number
2) Subtract two numbers
3) Convert months to years
4) Convert years to months
5) Roll dice
6) Exit
-> 4
Enter a number: 30
30 years equals 360 months

1) Square a number
2) Subtract two numbers
3) Convert months to years
4) Convert years to months
5) Roll dice
6) Exit
-> 5
You rolled a 4 and a 5 for a total of 9

1) Square a number
2) Subtract two numbers
3) Convert months to years
4) Convert years to months
5) Roll dice
6) Exit
-> 6
Goodbye

Tips, Tricks, and Reflection

It’s not a big deal, but we are repeating the following statement frequently: float(input("Enter a number: ")). It may not be a bad idea to extract this code into a small function.