Chapter 5 Iteration

How to compute factorial ?

Factorial n! = n * (n - 1) * (n - 2) * ... * 2 * 1

Example

Object: compute 4!

Steps:

result = 1

result *= 2

result *= 3

result *= 4

print(result)

In sequential way?

What if n is a large number?

Iteration / Looping

 —— process of executing the same section of code over and over

for statement

while statement

Iteration / Looping

 —— process of executing the same section of code over and over

while statement

Iteration / Looping

 —— process of executing the same section of code over and over

while statement

used for checking input (positive integer)

Iteration / Looping

 —— process of executing the same section of code over and over

for statement

Iteration / Looping

 —— process of executing the same section of code over and over

for statement

keyword: in

for i in 1,2,4,8:

   print(i)

for i in range (1, 10, 2):

    print(i)

for letter in 'word':

   print letter

Iteration / Looping

 —— process of executing the same section of code over and over

for statement

range (begin, end, step)

• begin is the first value in the range; if omitted, the default value is 0
• end is one past the last value in the range; the end value is always required and may not be omitted
• step is the amount to increment or decrement; if the step parameter is omitted, it defaults to 1(counts up by ones)

Iteration / Looping

 —— process of executing the same section of code over and over

nested loop

print a multiplication table in the following form

Iteration / Looping

 —— process of executing the same section of code over and over

nested loop

print a multiplication table in the following form

Iteration / Looping

 —— process of executing the same section of code over and over

abnormal loop termination

break:  implement middle-exiting loop control logic

continue:  skips the rest of the body of the loop and immediately checks the loop’s condition

result: 11175

result: 5050

Iteration / Looping

 —— process of executing the same section of code over and over

while/else & for/else