[Python-3000] Announcing PEP 3136

[Guido van Rossum]

On 6/30/07, Matt Chisholm <matt-python at theory.org> wrote:
> I've created and submitted a new PEP proposing support for labels in
> Python's break and continue statements.  Georg Brandl has graciously
> added it to the PEP list as PEP 3136:
>
> http://www.python.org/dev/peps/pep-3136/

I think this is a good summary of various proposals that have been
floated in the past, plus some new ones. As a PEP, it falls short
because it doesn't pick a solution but merely offers a large menu of
possible options. Also, there is nothing about implementation yet.

However, I'm rejecting it on the basis that code so complicated to
require this feature is very rare. In most cases there are existing
work-arounds that produce clean code, for example using 'return'.
While I'm sure there are some (rare) real cases where clarity of the
code would suffer from a refactoring that makes it possible to use
return, this is offset by two issues:

1. The complexity added to the language, permanently. This affects not
only all Python implementations, but also every source analysis tool,
plus of course all documentation for the language.

2. My expectation that the feature will be abused more than it will be
used right, leading to a net decrease in code clarity (measured across
all Python code written henceforth). Lazy programmers are everywhere,
and before you know it you have an incredible mess on your hands of
unintelligible code.

I realize this is a heavy bar to pass, and somewhat subjective. That's
okay. There is real value in having a small language. Also, as I said,
while there are no past PEPs to document it, this has been brought up
and rejected many times before.

-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)