[Tutor] Question on Functions

[Josh Gregorio]

Thank you. I didn't really understand how to use return until now.
Josh

----- Original Message -----
From: Andrei Kulakov <sill@optonline.net>
To: <tutor@python.org>
Sent: Wednesday, October 03, 2001 1:03 AM
Subject: Re: [Tutor] Question on Functions


> On Wed, Oct 03, 2001 at 01:12:21AM -0700, Josh Gregorio wrote:
> > I am not sure I understand how to properly use functions (or when to use
them). Suppose you had some code like this:
> >
> > x = 1
> > y = 2
> >
> > def add(a,b):
> >    c = a + b
> >    print c
> >
> >
> > add(x,y)
> >
> > print x,y
> >
> > Is there a way to store the result of a+b into a variable that is
accessible outside of the function? Could you, for instance, add x and y,
print the result c, and then update x to equal the result of x + y (from
within a function)?
>
> Certainly..:
>
> def add(a, b):
>     return a + b
>
> result = add(x, y)
>
> print result    # prints 3
>
> In general, functions are used to package some repeating algorithm up.
> Let's say you have this:
>
> print "x + z is", x + z
> print "y + a is", y + a
> [100 more lines of the sort]
>
> Now, you could make a function add() like the one above, to print the
> result. In this case there's not much point to it because it's as easy to
> type x + z as add(x, z), even easier. What if you had a function that
> spanned 30 lines and you needed its output for different values in 100
> places in your program? You could either write one 30 line function and
> call it from 100 places (totalling 130 lines) or you could reproduce the
> same logic on each of the 100 lines, giving you 100 * 30 - 3000 lines. One
> problem here is that it's a lot more typing, another problem is that if
> you want to change the function (like you found a bug or something), it's
> much easier to change it in one places instead of changing it in 100
> places.
>
> Typically, make a function if you see that there's a few places in your
> program that use the same algorithm logic and you can save yourself typing
> effort by using a function.
>
> >
> > Thank you,
> > Josh
> >
> > PS Could anyone recommend some good exercises to do to get more
practice/understanding?
>
> --
> Cymbaline: intelligent learning mp3 player - python, linux, console.
> get it at: cy.silmarill.org
>
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