Question

I keep getting an error whenever I enter this code (I’m a python noob so I’m probably missing something obvious)

def expadd(num, exp):
    while ((num and exp) != (1001)):
        return (num ^ exp) + expadd((num + 1), (exp + 1))
    return 0
buffer = str(expadd(1000, 1000)
total = 0 #error here "syntax error"
for i in range(1,10):
    total = total +  int(buffer[-i])
print total

Answer 1

Besides the syntax error, there is also a logical error:

while ((num and exp) != (1001)):

will always be True, because both 0 and 1 are different from 1001. (num and exp) checks if both num and exp are Trueish (which, for numbers, is the case if they are not 0). The result of this will either be 1 (True) or 0 (False), and both of them are different from 1001.

Then, @interjay noted correctly that you should be using if, not while.

You probably meant

if (num != 1001) and (exp != 1001):

(the parentheses are not necessary, I just added them for clarity)

Also, ^ is binary xor, not exponentiation. That is the ** operator:

>>> 2^4
6
>>> 2**4
16