Iterative statements

Iterative statements: In some programs, certain set of statements are executed again and again based

upon conditional test. i.e executed more than one time. This type of execution is called looping or

iteration. Looping statement in python is implemented by using 'for' and 'while' statement.

Syntax: (for loop)

for variable in range(start,stop+1,step):

 statements

Syntax: (while loop)

while (condition):

 Statements

Example:

1. Write a program to input any number and to print all natural numbers up to given number.

Code:

n = input("enter any number")

for i in range(1,n+1):

print i,

Output:

enter any number10

1 2 3 4 5 6 7 8 9 10

2. Write a program to input any number and to find sum of all natural numbers up to given number.

Code:

n = input("Enter any number")

sum= 0

for i in range(1,n+1):

 sum = sum+i

print "sum=",sum

Output:

Enter any number5

sum = 15

3. Write a program to input any number and to find reverse of that number.

Code:

n = input("Enter any number")

r = 0

while(n>0):

 r = r*10+n%10

 n = n/10

print "reverse number is", r

Output:

>>> 

Enter any number345

reverse number is 543

>>> 

Example: Write the output from the following code:

1. sum = 0

for i in range(1,11,2):

sum+ = i

print "sum = ", sum

output:

sum = 25

2. sum = 0

i = 4

while (i<=20):

sum+=i

i+= 4

print "Sum = ",sum

output:

Sum = 60

Example: Interchange for loop into while loop

1. for i in range(10,26,2):

print i

Ans:

i=10

while(i<26):

print i

i+=2

2. s=0

for i in range(10,50,10):

 s + =i

print " Sum= ", s

Ans:

s = 0

i = 10

while(i<50):

s+ = i

i+ = 10

print "Sum=",s

Example: Interchange while loop in to for loop.

i = 5

s = 0

while (i<25):

s+ = i

i + = 5

print " Sum =", s

Ans:

s = 0

for i in range(5,25,5):

s+=i

print "Sum = ", s