Not all of arguments converted during string formatting

You're putting the string formatting in the wrong place; it needs to be right after the string that's being formatted:

f = open("%s.sql" % (today), "w")

It's legal to not pass any formatting arguments, like you did with "%s.sql", but it's not legal to pass arguments but not the right amount ("w" % (today) passes one, but there's no string formatting in "w", so you get an error that not all of the arguments were used)

f = open("%s.sql" % today, "w")