I need some help debugging my code. I am trying to create a calculator in python. I can't figure out what I'm doing wrong. Here is my code:

def calculate(n):

# Prompts user for an operation.

operation = raw_input("Pick an operation. Type 'ex' for exponentiation, 'add' for addition, 'sub' for subtraction, 'times' for multiplication, 'div' for division, and 'mod' for modulo: "

# When using exponentiation:

if operation == 'ex':

power = raw_input("Pick an exponent: ")

p = power

return n**p

# When using addition:

elif operation == 'add':

addend = raw_input("What would you like to add %s to?" % (n))

add = addend

return n + add

# When using subtraction:

elif operation == 'sub':

minuend = raw_input("What would you like to subtract %s from?" % (n))

mino = minuend

return mino - n

# When using multiplication:

elif operation == 'times':

factor = raw_input("What would you like to multiply %s by?" % (n))

fact = factor

return n * fact

# When using division:

elif operation == 'div':

denom = raw_input("What would you like to divide %s by?" % (n))

den = denom

return n / den

# When finding remainders (modulo):

elif operation == 'mod':

modulus = raw_input("What would you like to find the remainder of by dividing %s by?")

mod = modulus

return n % mod

# When other operation is given / no operation:

else:

print "I'm sorry, could you please try again? Run this code again."

# Type "print calculate(number)" and follow instructions:

print calculate(3)