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Highlights from this chapter include:

  • A while loop runs a set of statements, known as the loop body, while a given condition, known as the loop expression, is true.
  • A for loop can be used to iterate over elements of a container object.
  • A range() function generates a sequence of integers between the two numbers given a step size.
  • A nested loop has one or more loops within the body of another loop.
  • A break statement is used within a for or a while loop to allow the program execution to exit the loop once a given condition is triggered.
  • A continue statement allows for skipping the execution of the remainder of the loop without exiting the loop entirely.
  • A loop else statement runs after the loop's execution is completed without being interrupted by a break statement.

At this point, you should be able to write programs with loop constructs. The programming practice below ties together most topics presented in the chapter.

Function Description

range(end)

Generates a sequence beginning at 0 until
end
with step size of 1.

range(start, end)

Generates a sequence beginning at start until end with step size of 1.

range(start, end, s)

Generates a sequence beginning at start until end with the step size of s.

Loop constructs Description

while loop

    # initialization
    while expression:
      # loop body

    # statements after the loop
    

for loop

    # initialization
    for loop_variable in container:
      # loop body

    # statements after the loop
    

Nested while loop

    while outer_loop_expression:
      # outer loop body (1)
      while inner_loop_expression:
        # inner loop body
      # outer loop body (2)

    # statements after the loop
    

break statement

    # initialization
    while loop_expression:
      # loop body
      if break_condition:
        break
      # remaining body of loop

    # statements after the loop
    

continue statement

    # initialization
    while loop_expression:
      # loop body
      if continue_condition:
        continue
      # remaining body of loop

    # statements after the loop
    

Loop else statement

    # initialization
    for loop_expression:
      # loop body
      if break_condition:
        break
      # remaining body of loop
    else:
      # loop else statement
    
    # statements after the loop
    
Table 5.4 Chapter 5 reference.

Try It

Prime numbers

Write a program that takes in a positive integer number (N) and prints out the first N prime numbers on separate lines.

Note: A prime number is a number that is not divisible by any positive number larger than 1. To check whether a number is prime, the condition of number % i != 0 can be checked for i greater than 1 and less than number.

Ex: if N = 6, the output is:

    2
    3
    5
    7
    11
    13
    
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