Random "None" appears, no clue why

Question

Hi,

I've defined a function that adds up all the numbers in a list and gives you the total. Works like a charm, but each time I run it I also get "None" on the line below. Does anyone know what's causing this? Here's the definition:

def listTotal(listname):
f=0
total=0
while 1==1:
assert(listname[f]==float(listname[f])),"Your list should only contain numbers!"
total = total +listname[f]
f=f+1
if f == len(listname):
print (total)
break

Thanks in advance!

Answer 1

How are you calling your function? Like this?

print(listTotal(your_list))

In that case, the None is the return value of your function - it has none!

Either you just call the function without embedding it in a print call, or - probably more natural - you write:

return total

instead of

print(total)

in your function.

You also don't need the break.

Answer 2

To add to HonFu
If you do print(print('x')) the output will be:
X
None
Because the print function
returns None.