import os

def printLargest(x, y, z):
    "Takes three numbers and prints the largest of them"
    # Initiate variable to hold largest number and assign it the first number
    largest = x; 

    # Iterate over passed numbers
    for number in (x, y, z):
        # Test if current number is larger than value stored in variable
        # If so, replace value of variable
        if number > largest:
            largest = number

    # Print value stored in variable
    print(largest)
    return

# Clear screen
os.system("clear")  # Mac or Linux
# os.system("cls")  # Windows

# Call to function printLargest with three parameters
printLargest(42, 12, 900)