OP solved it, closing

Which tests? Please state the input values. Which language?

3 of textcases are giving incorrect results

Closing.

Closing.

If you ask this question, you did not understand the kata. Read the description carefully, you'll find the answer, it's very clear.

The return line of this function will call the function itself as needed until a condition is met. This is known as recursion. Here's an alternate source.

how can you use your function iside the function in the last line

The error message reveals that your code is trying to access an element at an index not within range of the indices for this object. This most likely occurs at arr[i+1].

I passed 3 tests but I get this error
Traceback (most recent call last):
File "tests.py", line 42, in
test.assert_equals(dirReduc(a), [])
File "/workspace/default/solution.py", line 3, in dirReduc
if arr[i]=="SOUTH" and arr[i+1]=="NORTH":
IndexError: list index out of range

I figured it out myself

my code is similar to this