Append not working

[deanhystad]

append is a function that returns None. It does not return the list with an appended value.

Your code does not make any sense. It does this:
tag[N].append(tag[N].get('data_id') for N in range(len(tag))

id = []  #<-  This list is thrown away in the next line
for id in tag:
    data_id = id.get('data-id')
    print(id.append(data_id),str(data_id))
    #load id array list
    id.append(data_id)  # This is id from the for loop