[Python-Dev] Readability vs. Understanding

[M.-A. Lemburg]

Guido van Rossum wrote:
> There's also the tension between making the language simpler (to
> learn) and making programs simpler (to read).  For example, *if* (and
> that's still a very big if) we were to add a language feature that
> would let you write
> 
>     synchronized(lock):
>         BLOCK
> 
> instead of
> 
>     lock.aqcuire()
>     try:
>         BLOCK
>     finally:
>         lock.release()
> 
> I assure you that this makes programs that use locks more readable,
> which reduces maintenance costs down the road.  But at the same time
> we can't hope to reduce every idiom to a single statement, and we must
> be careful not to destroy the language by adding too many "neat
> tricks".

I think you're getting this wrong:

By introducing meta-constructs like the thunk idea to raise the
expressiveness of random program blocks you do make the program
simpler to read, but certainly not easier to comprehend.

The reason is that arbitrary code gets hidden from the user in
a way which makes it hard to actually follow the flow of
commands.

The above lock example is perfect for this: the try:finally:
approach is clear and explicit whereas the synchronized(lock):
block introduces a layer of abstraction that is not easy to
comprehend: because the flow of control is not obvious
anymore and because it is hidden in some definition of
synchronized() which the maintainer will have to look up
somewhere (where somewhere could be inside some .zip archive
holding the great new toolbox some geek developer which has
long left the company found cool to use... :-/).

We have already introduced such a meta-contruct feature in a
few places, e.g. importers and meta-classes... both are hardly ever
used and that's good, because understanding, maintaining and
possibly debugging these is a nightmare for much the same
reason that thunks are.

Now, we're lucky since meta-classes or writing importers is
not all that easy. With thunks the situation will be much like
giving macros to Python programmers: you'll see a proliferation
of new meta-constructs in all kinds of programs and in the
end lose the maintainability argument which is still one
of the strongest ones for using Python in the first place.

-- 
Marc-Andre Lemburg
CEO eGenix.com Software GmbH
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