What does this error mean? and how is it fixed

Have you completed the entire notebook and passed all of its unit tests?

In this assignment, you cannot grade a partially-completed notebook.

yes i did

You can search the notebook to see where the word “None” or the operator += is used. Please post a screen capture image of that section of the notebook.

Try replacing compound arithmetic operator ‘a += b’ with explicit operation ‘a = a + b’.

This error means that you are using some operator ‘+=’ in this case that is not defined for these operands. Numpy do not have overloaded operator for some compound operations. ‘/=’ is one of them but I do not know about ‘+=’.

Yes, that’s good advice in general!

i will try that

is it maybe this part?

Yes. You haven’t completed that part of the assignment.

That’s why I asked if you had completed the assignment and passed all of the unit tests.

my bad i had the code written before the notebook didnt save my work
thx for your help

Autosave doesn’t work very well on Coursera’s platform. Always remember to use the “Save” button before you submit for grading.