The code works when I run it in VS Code so that's why I was confused. I still don't understand how my code can pass all the tests and still produce an error.

So for this kata I wrote a solution that did not manipulate the original list. I passed all of the tests but when I go to attempt my soultion I passed all 4 tests and then get an STDERR: error that says this:

Traceback (most recent call last):
File "main.py", line 16, in
Test.assert_equals(binary_array_to_number(array), n,"It should work for random inputs too")
File "/home/codewarrior/solution.py", line 13, in binary_array_to_number
num.append(digit * binary[ind])
KeyError: 4

Does anyone know how to fix this?
P.S I did not use the reverse() as I see in other comments