On Wed, Oct 20, 2010 at 03:13, Steven D'Aprano <st...@pearwood.info> wrote:
> Let's start with an easy example: factorial(0). When Python sees > factorial(0), it does this: > > Call factorial with argument 0: > * if n == 0 <-- this is true, so execute the "if" block: > return 1 > > so the function factorial(0) returns the value 1. All that goes on > behind the scenes. What *we* see is: > >>>> factorial(0) > 1 > > That part is easy. Now, the recursive part. What does Python do when you > call factorial(1)? > > Call factorial with argument 1: > * if n == 0 <-- this is false, so execute the "else" block: > recurse = factorial(n-1) > > Here Python is calling a function. It happens to be the same function, > but Python doesn't care about that, and neither should you. So Python > simply continues: > > Call factorial with argument 1-1 = 0: > > Now, we've already seen this above, but Python does the simplest thing > that could work: it calculates the answer from scratch: > I won't quote the whole thing, which should be enshrined somewhere. I just wanted to note that Steven is a great teacher! Dick Moores (teacher, retired) _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
