[Tutor] Why is this write defined as a tuple, instead of picking list?

[Adam]

I'm using this function to cycle through a list and add some
formatting to it to prepare it for saving: 

def prepare_for_saving(article_items):
    """This function formats the article_items list 
so that it's in HTML format and looks nice"""
    print "article_items is type: ", type(article_items)
    for x in article_items:
        write = "<h3>", article_items[0], "</h3>"
        print "write is type: ", type(write)
    #write = str(article_items)#deprecated - replaced by the
formatting loop    return (write)

At the time article_items is passed it is a list - however,
when I try to do the formatting with write =, write is
declared as a tuple - why is this, and how can I force it to
be a string (I believe I need a string for the file saving
function?)

Thanks
adam