"Dick Moores" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] > Encapsulate the while loop in a generator: > def count(limit): > n=0 > while n<limit: > yield n > n += 1 > > All 3 are essentially the same, aren't they. Which makes me feel > even > dumber, because I don't understand any of them. I've consulted 3 > books, and still don't understand the use of yield.
Think of yield as being the same as return except that next time you "call the function" all the state is preserved and it picks up processing after the yield. So first time you call count above it returns 0 next time you call it it executes the n+= 1 and goes round the loop again until it hits yield when it returns 1. next time you call it executes y+=1 again, but because the state has been remembered n goes to 2 and yield returns that and so on until you reach n = limit at which point it just exits with StopIteration. Here is a short example: >>> def y(n): ... j = 0 ... while j < n: ... yield j ... j += 1 ... >>> try: ... x = y(7) ... for n in range(20): ... print x.next() ... except StopIteration: ... print 'Reached the end' ... 0 1 2 3 4 5 6 Reached the end >>> Does that help? -- Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
