I don't understand what is wrong with my code.

I am trying to add positive values of a list.

Here is my code:

def sam(n):for x in n:if x > 0:return sum(x)

You never actually create a value to add to. You are adding one value to a list per in iteration.

Just in iterate through the list and add them manually:

def sam(n): value = 0for x in n:if x > 0:value += xreturn value

Or you could do it in one line:

def sam(n):return sum(x for x in n if x > 0)

For better practice you should choose better variables. More meaningful variables are easier to remember and makes your code more readable:

So n could be num_list (or number_list).

Rather than iterate with x you could use number. This tells you that number contains a single letter.