Single line if statement with a continue

[Weatherby,Gerard]

I once saw a C function full of GOTOs which jumped to the return state at the bottom of the functions because the programmer had learned that “multiple returns are a bad idea.”

I totally agree multiple returns causing confusion is a symptom of poor design, not a cause.

Required cleanup is easily handled by the try / finally construct.

From: Python-list <python-list-bounces+gweatherby=uchc.edu at python.org> on behalf of avi.e.gross at gmail.com <avi.e.gross at gmail.com>
Date: Thursday, December 15, 2022 at 2:07 PM
To: python-list at python.org <python-list at python.org>
Subject: RE: Single line if statement with a continue
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Multiple returns is not always a problem as it depends on the nature of a
task whether it has complex enough cases.

I have seen code that instead sets Boolean variables when it is ready to
return and everything else keeps checking the variables to skip further
processing so the program then slides down to a single return statement. If
done properly, it boils down to the same result if VERY carefully done but
with lots of sometimes complex IF statements that may be not be updated well
if the logic changes a bit.

In such cases, I vastly prefer clean and unambiguous returns  from the
function right at the point where the decision is made, UNLESS the exit is
not always clean as there may be cleanup or finalization of some kind
required that is best done at a single point.

If efficiency is an issue, then clearly a rapid exit may beat one where
processing continues for a while and also often beats a method that involves
creating and calling multiple smaller functions with lots of overhead.

Having said all that, of course, if you can find a fairly simple algorithm
that only returns from one place, use it instead of a convoluted one. The
issue is not necessarily that multiple return points are bad, but that they
are often a symptom of sloppy planning. But for some problems, they fit well
and simplify things.

-----Original Message-----
From: Python-list <python-list-bounces+avi.e.gross=gmail.com at python.org> On
Behalf Of Stefan Ram
Sent: Thursday, December 15, 2022 7:42 AM
To: python-list at python.org
Subject: Re: Single line if statement with a continue

Chris Green <cl at isbd.net> writes:
>I always try to avoid multiple returns from functions/methods, as soon
>as things get complex it's all to easy to miss clean-up etc.

  This "complexity" could also mean that the function has
  become too large. In such a case, one could say that the
  /size/ of the function is the actual cause of problems
  and not multiple returns.

|Fools ignore complexity. Pragmatists suffer it. Some can avoid it.
|Geniuses remove it.
Alan Perlis (1922/1990)

  Within a small function, multiple returns are rarely
  a problem.

  When a function is large, one can apply well-known
  refactors. For an example, look at the code in the
  first post of the thread

Python script not letting go of files
Date: Tue, 29 Nov 2022 12:52:15 +0000

  and then at my reply of

29 Nov 2022 14:44:39 GMT.

>"No multiple returns" is often found in programming guidelines.

  I religiously followed that when I did more C programming
  than today. Then, I read an article about how the result
  pattern makes functions measurably slower. (It should not
  with an optimizing compiler, but it did due to those
  measurements. Can't find that article now, though.)

  "Result pattern" I call writing,

if a:
    result = 123
else:
    result = 456
return result

  , instead of,

if a:
    return 123
else
    return 456

  .


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