Why is my string empty?

[karabakh]

When I add the ids to some list, the list is not being overwritten.

That's because you're using a method of the list that modifies it, like list.append(). What you're not doing is reassigning the list each time through like list = [new_item].

With strings, you'd instead assign the existing part and the new part to a variable. Something like:

full_string = ""
for s in list:
    full_string += s  # Keeps the existing portion each time through the loop.

Thank you. I also discovered extend which seems to be what you are mentioning here.