# Python Training and Exercises : Loops

## While loop examples

```a = 5

b = 1

while b <= 5:

print ("%d * %d = %d" %(a, b, a*b))

b+=1

----------Output---------

5 * 1 = 5
5 * 2 = 10
5 * 3 = 15
5 * 4 = 20
5 * 5 = 25

```

## While with “else”

```
a = 1

while a <= 3:

b = int (input ("enter a no: "))

if b == 0:

print ("exiting loop with break command, 'else' is not executed")

break

a+=1

else:

print ("loop exited without executing break command")

'''
In the above program, if your input is 0, while loop will "break" and the code
inside "else" clause will not get executed.
If you are using other numbers as inputs, while loop will complete its full cycle
and the code inside "else" clause will be considered
'''

```

```
a = 1

while a < 10:

print (a, end=',')

a+=1

----------Output---------

1,2,3,4,5,6,7,8,9,

a = 1

while a < 10:

print (a, end=' ')

a+=1

----------Output---------

1 2 3 4 5 6 7 8 9

```

## For loop and Range function

```
for a in range(10):

print (a, end=" ")

----------Output---------

0 1 2 3 4 5 6 7 8 9

a = 5

for b in range(1, 5):

print ("%d * %d = %d" %(a, b, a*b))

----------Output---------

5 * 1 = 5
5 * 2 = 10
5 * 3 = 15
5 * 4 = 20

a = [10,20,30,40,50]

for b in a:

print (b+5, end=" ")

----------Output---------

15 25 35 45 55

```

## Python Exercises

1. Write a python program to print the square of all numbers from 0 to 10

2. Write a python program to find the sum of all even numbers from 0 to 10

3. Write a python program to read three numbers (a,b,c) and check how many numbers between ‘a’ and ‘b’ are divisible by ‘c’

4. Write a python program to get the following output

1-----99

2-----98

3-----97

. .

. .

. .

98-----2

99-----1

5. Write a python program to read a number and print the binary of that number (hint: if ‘a’ is a string , a[::-1] will be reverse of that string)

6. Write a python program to read four numbers (representing the four octets of an IP) and print the next five IP address

Eg:

Input:

192 168 255 252

----------Output---------

192 168 255 253

192 168 255 254

192 168 255 255

192 169 0 0

192 169 0 1

7. Write a python program to print the factorial of a given number

8. Write a python program to print the first 10 numbers Fibonacci series

9. Write a python program to read a number and print a right triangle using "*"

Eg :

Input : 5

----------Output---------

*

* *

* * *

* * * *

* * * * *

10. Write a python program to check given number is prime or not

11. Write a python program to print all prime numbers between 0 to 100 , and print how many prime numbers are there.

12. a, b, c = 0, 0, 0 . Write a python program to print all permutations using those three variables

Output : 000 , 001 ,002, 003, 004, 0005 ,006, 007, 008, 009, 010, 011 …… 999

Next chapter: Python training : Strings and String Methods