Twitter notification platform also accepting user_id

I have the needed user_id the current script tries to prob the api for via the supplied screen_name (username) I’m also encountering an error related to trying to obtain the user_id most recently.
Have the option to suply the username or the user_id would have helped me in this instance.

It is using the GET/users/lookup method to grab a single user’s info. Why not user GET/users/show? Just curious as my error seems to relate to grabbing key 0 info from a single user query on the lookup method.