Stuff

def verify_isbn_file(isbn_file):    '''verify_isbn_file(file) -> boolean        Will print out all the invalid ISBNs in the given text file. If the     parameter given is not a file, will return False.'''    if ( type(isbn_file) != file ):        return False        print "Invalid ISBN's in file:"     for isbn_line in isbn_file:        isbn_line = isbn_line.replace('\n', '')        if ( verify_isbn(isbn_line) == False ):            print isbn_line    af = open('isbn_file.txt')verify_isbn_file(af)