What meaning of this ""hello %s you are %s years old" % x"

[fl]

Hi,

I get a post on tuple, see below please, on line. It seems that something is 
missing. I want to learn tuple from this example as well.

Could you explain it to me (a tuple % another tuple)?


Thanks,






http://stackoverflow.com/questions/1708510/python-list-vs-tuple-when-to-use-each

In Python, when should you use lists and when tuples?

Sometimes you don't have a choice, for example if you have

"hello %s you are %s years old" % x
then x must be a tuple.

But if I am the one who designs the API and gets to choose the data types, then 
what are the guidelines?