Application in CodeCraft

addTo(n) function

Build n columns with heights from 1 to n, then build a tall column that has height the sum of (1 + 2 + ... + n).

def addTo(n):
    sum = 0
    i = 1
    while i <= n:
        column(i, -20, i, 'box_light_blue')
        sum += i
        i += 1

    column(-2, -20, sum,'box_red')

# call the function with input    
addTo(5)

In the picture below, the blue columns indicate the values of i (1, 2, 3, 4, 5) as the computer runs through the while loop, and the red tall column at the left is the sum of all numbers: 1+2+...+5 = 15.

More than one condition in a while loop

#two conditions
i, h = 5, 3
while i < 10 and h < 50:
  column(i, -20, h, 'box_pink')
  i += 1
  h += 1

i (x location) increases from 5 to 9;
h (the column height) increases from 3 to 7.

In this case, i reaches 10 before h can reach 50, so i < 10 limits the loop.

Factorials

We can use a while loop to calculate factorials. Do you remember factorials? For example, 4! = 4 * 3 * 2 * 1

# while loop to calculate factorial of n
def while_fact():
    n = int(input( 'Enter an integer >= 0: '))
    fact = 1
    i=2
    while i <= n:
        fact *= i
        i += 1  

    column(n, -10, n, 'brick')
    column(n, -12, fact, 'obsidian')

# call the function
while_fact()          # enter n as 4

We can also use a for loop to calculate factorials:

# for loop to calculate factorial of n  
def for_fact():
    n = int(input('Enter an integer >= 0: '))
    column(-n, -10, n, 'brick')

    fact = 1
    for i in range (2, n+1):
        fact *= i                # same as fact = fact *i 
    column(-n, -12, fact, 'obsidian')

# call the function
for_fact()        # enter n as 4

Run and input the same number for both applications. In this image, you can see that they give the same results: the brick column is n blocks high, and the black column is n! blocks high.