Perimeter and area of a circle and finding Natural Exponential Function

import math
r=int(raw_input('Enter the radius of circle:'))
perimeter=2*math.pi*r
print 'Perimeter of a circle :',perimeter
area=math.pi*(r**2)
print 'Area of acircle :',area

x=int(raw_input('Enter the value of x in y=e**x:'))
y=math.e**x
print 'Natural Exponential Function value :',y