python - How to check for a necessary input of raw_input? -

i've started learn python day ago, seems easy, still have questions :)

how write script have check necessary input of raw_input?

i mean, script must stop if user have not entered case , hit enter on raw_input...

ans = raw_input('enter: ') if not ans:     print "you entered nothing!" else:     print "you entered something!" 

if user hits enter, ans ''. , '' considered false, condition true (not false), if block run.

if wish continually ask user input, can use while-loop:

ans = '' while not ans: # while input given empty string     ans = raw_input('enter: ')