```
# nth_prime.py
def nth_prime(n):
primes = [2]
test_int = 1
while len(primes) < n:
test_int += 2
for p in primes:
if test_int % p is 0:
break
else:
if p is primes[len(primes)]:
primes.add(test_int)
return primes[n - 1]
while True:
try:
num = int(input("Enter a number:\n"))
print(nth_prime(num))
except ValueError:
print("NaN. Try again!")
```

It should add prime numbers to the list until the length of the list is equal to n and return the last number in the list. For some reason it crashes once a number is entered. I've looked over it but I can't seem to find what's wrong.