Nothing - "p" is a dummy character so the program goes straight to the raw_input.
Sniper, I think it's awesome. A couple of things: decide whether you're going to use spacing around your operators or not (I recommend you do) this:
2+2=4 # evil!
2 + 2 = 4 # woo!
Also, as Klipt said, use math.pi:
import math
def area_circle(radius):
return math.pi * radius ** 2
# better - this doesn't import the whole damn math library:
from math import pi
def area_circle(radius):
return pi * radius ** 2
# you don't need the "math." as you're specifying the thingy you want to use (pi)