First argument of sys.path.insert in python

Question

Some examples show

sys.path.insert(0, "path/to/whatever")

and other examples show

sys.path.insert(1, "path/to/whatever").

But I could not find any information of regarding the effect of using 0 as opposed to 1 and vice versa, for the first input argument of the insert() function.

Where can I find official documentation regarding this?

Also what is the difference between the two?

Answer 1

sys.path is a list, and so, of course, supports all list methods with their exact semantics.

But for sys.path specifically, element 0 is the path containing the script, and so using index 1 causes Python to search that path first and then the inserted path, versus the other way around when inserted at index 0.