Simple calculator using if elseif else and nested if else

a=int(raw_input('Enter the value of a:'))
b=int(raw_input('Enter the value of b:'))
print ' 1. add  2.sub  3.mul  4. div  5.exp'
n=int(raw_input('Enter the choice:'))
if n==1:
      c=a+b
      print 'Added value is:',c
elif n==2:
      if a>b:     #Nested if else
            c=a-b
            print 'Subtracted value is:',c
      else:
            c=b-a
            print 'Subtracted value is:',c
elif n==3:
      c=a*b
      print 'Multiplication value is:',c
elif n==4:
      if b==0:          #Nested if else
            print 'Division by zero not defined'
      else:
            c=float(a)/b
            print 'Divison value is:',c
elif n==5:
      c=a**b
      print 'Exponent value is:',c
else:
      print 'Invalid options'

Factorial using while loop

f=i=1
n=int(raw_input('Enter the number: '))
while i<=n:
      f=f*i
      i=i+1
print f

To check the number is Prime or Not

n=int(raw_input('Enter the number to check:'))
flag=0
i=2
while(i<=(n/2)):
    if (n%i==0):
        flag=1
    i=i+1
if(flag==0):
    print  'The number ',n, ' is prime number'
else:
    print 'The number ',n, ' is not prime number'

Factorial using Recursion

def recur_factorial(n):
   if n == 1:
       return n
   else:
       return n*recur_factorial(n-1)


num = int(input("Enter a number: "))

if num < 0:
   print("Sorry, factorial does not exist for negative numbers")
elif num == 0:
   print("The factorial of 0 is 1")
else:
   print("The factorial of",num,"is",recur_factorial(num))

Searching the character count from string

word = raw_input('Enter the String:')
char = raw_input('Enter the Character to search:')

count = 0
for letter in word:
 if letter == char:
  count = count + 1
print 'Number of times repeated:', count