So, the standard factorial function in python is defined as:

```
def factorial(x):
  if x == 0:
    return 1
  else:
    return x * factorial(x-1)

```

Since n! := n \* (n-1) \* ... \* 1, we can write n! as (n+1)! / (n+1). Thus 0! = 1 and we wouldn't need that if x == 0. I tried to write that in python to but I didn't work. Can you guys help me?