Looping constructs in Python while and for

• Repeat with While:
  • This is simplest mechanism for looping
  • The syntax is

  while <conditional expression>:
      # code block
  

  • Examples
  • Lets try to write a program which prints all the even numbers between 10 and 50
  • Lets write a program to find the factors of a given number

    number = int(input('Enter the number: '))
    index = 2
    while index < number:
        if number%index == 0:
            print(index)
        index += 1
  
  

  • Lets modify the above program to print only last 5 factors

    number = int(input('Enter the number: '))
    index = number -1
    factors_found = 0
    while index >= 2:
        if number%index == 0:
            if factors_found < 5:
                print(index)
                factors_found += 1
                if factors_found == 5:
                    break
            
        index -= 1 
  
  

  • Exercise: Write a python program to find out if the number given is prime or not

    number = int(input('Enter the number: '))
    index = 2
    is_prime = True
    while index < number:
        if number%index == 0:
            is_prime = False
            break
        index += 1
  
    if is_prime:
        print(f"{number} is prime")
    else:
        print(f"{number} is not prime")
  

  • Exercise: Extend the program to print all the prime numbers between 10 and 100