Quoting Alberto Troiano <[EMAIL PROTECTED]>: > Please let's talk about this more! *grin* > I'm not sure if I'm following you, what I see here is a function inside > other function and the first function returns its inside function, but > how does it work?
In Python, as in other modern languages, functions are "first-class" objects. In particular, you can pass functions as arguments to other functions, or return functions from other functions. I like examples: >>> def add(x, y): ... return x + y ... >>> f = add # Notice the lack of brackets after 'add' >>> f(3, 5) 8 >>> f(9, 12) 21 In this case, all I've done is assigned to f the function 'add'. This means that f is now a function, and I can call it, even though I never did 'def f(x, y)' anywhere. >>> def square(x): ... return x*x ... >>> range(10) [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] >>> map(square, range(10)) [0, 1, 4, 9, 16, 25, 36, 49, 64, 81] The 'map' builtin function takes two arguments: a function and a list. It makes a new list by applying the function to each element of the old list. ie: This is an example of passing a functino as an argument. Finally: >>> def makeAdder(x): ... def add(y): ... return x + y ... return add ... >>> f = makeAdder(5) >>> f(3) 8 >>> f(8) 13 'def add(y)' defines a function of one argument, which adds that argument to x, and returns the result. What is x? Well, x is a variable in the scope of makeAdder(); it gets bound to the argument you pass. In my example, x was bound to 5. So, effectively, we have created a new function by: 'def add(y): return 5 + y', and then returned that function to f. We can now call f and see the result. HTH! -- John. [ps: sorry for the troll.. I couldn't resist :-) ] _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
