I tend to agree on public APIs, however in this case of a helper function the use case with a join is really really common so this extra function comes in very handy. I also kept it using lists, so it's more obvious than tuples.

JFTR it wasn't my idea, so I'm not defensive about my own idea here. :)  I just re-implemented it for read_file b/c it's really handy and saves a lot of typing.