[Tutor] Multiple exits in a function...

[Danny Yoo]

On Fri, 24 Oct 2003, Alan Trautman wrote:

> In this case they should call the same exit function. Especially if you
> do any cleanup or logging. If they use different functions for each
> exit, do you really want to maintain two exit functions? Or as happens
> more often you forget one and that's the one your users will use causing
> a problem that will be very hard to troubleshoot.

Hi Alan,


Wait, wait, I think we're talking about something else.

Let's say we're writing a function that searches a list for an even
number.  If it can find it, the function will return it.  Otherwise, it'll
return -1.

Here's one way to write it:

###
def findEven(L):
    """Returns an even number out of list L.  If no such number exists,
    returns -1."""
    for x in L:
        if x % 2 == 0:
            return x
    return -1
###

This is a function with multiple "exits" out of the function: we get out
either through the first "return", or the "second" return.


There's another way of writing this so that there's only one 'return' out
of the function:

###
def findEven(L):
    """Returns an even number out of list L.  If no such number exists,
    returns -1."""
    result = -1
    for x in L:
        if x % 2 == 0:
            result = x
    return result
###

(The behavior of both functions is not quite equivalent.  That's why the
docstring doesn't say anything about returning the 'first' even number it
encounters.)


Talk to you later!