Summing a list of numbers - Printable Version +- Python Forum (https://python-forum.io) +-- Forum: Python Coding (https://python-forum.io/Forum-Python-Coding) +--- Forum: General Coding Help (https://python-forum.io/Forum-General-Coding-Help) +--- Thread: Summing a list of numbers (/Thread-Summing-a-list-of-numbers) Summing a list of numbers - Oldman45 - Jul-12-2020 I am teaching myself Python and following a YouTube tutorial I input the following: ```xs = [12, 14, 10] for num in xs: x += num print(x)```This works in the tutorial and sums the list to 36, but on my Python I get the following error message: ```Python 3.8.2 (tags/v3.8.2:7b3ab59, Feb 25 2020, 22:45:29) [MSC v.1916 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license()" for more information. >>> = RESTART: C:/Users/John/Documents/John''s files/Work/Coding/Think Like a Computer Scientist/Programmes/loop_exercise2a.py Traceback (most recent call last): File "C:/Users/John/Documents/John''s files/Work/Coding/Think Like a Computer Scientist/Programmes/loop_exercise2a.py", line 4, in x += num NameError: name 'x' is not defined >>> ```I would appreciate any advice or help. Thank you RE: Summing a list of numbers - Yoriz - Jul-12-2020 In the tutorial, they must have defined x to 0 ```x = 0 xs = [12, 14, 10] for num in xs: x += num print(x)`````Output:36`` RE: Summing a list of numbers - palladium - Jul-12-2020 You need to assign x to a value first. Try: ```xs = [12, 14, 10] x = 0 for num in xs: x += num print(x)```Or you can just use the sum function: ```xs = [12, 14, 10] x = sum(num for num in xs) print(x)``` RE: Summing a list of numbers - Yoriz - Jul-12-2020 (Jul-12-2020, 01:25 PM)palladium Wrote: Or you can just use the sum function: ```xs = [12, 14, 10] x = sum(num for num in xs) print(x)``` xs is already a list `num for num in xs` is making a list from a list `x = sum(xs)` is all that's needed. RE: Summing a list of numbers - palladium - Jul-12-2020 Thanks for pointing that out. I'm still quite new myself, haha. RE: Summing a list of numbers - sridhar - Jul-12-2020 You must declare x previously so that you can run without not defined error. Or you can try this simple sum function ```xs = [12, 14, 10] x = sum(xs) print(x)``` RE: Summing a list of numbers - Oldman45 - Jul-12-2020 Greetings Yoriz, Palladium and Sridhar Thank you all for the education - very useful. Yoriz, apologies for not complying with the rules. I have taken a copy of your link and next time I will comply. Sridhar I rated Yoriz and Palladium but the system said I had used my ratings up for the day when I tried to rate you so sorry. Thanks to you all again