sum
is built-in function, don't use it as name.If we solve it for you using numpy you still will not know numpy - i.e. this is not really helpful.
If you can't explain it to a six year old, you don't understand it yourself, Albert Einstein
How to Ask Questions The Smart Way: link and another link
Create MCV example
Debug small programs
How to Ask Questions The Smart Way: link and another link
Create MCV example
Debug small programs