[Python-Dev] #pragmas in Python source code

[M.-A. Lemburg]

Ka-Ping Yee wrote:
> 
> On Wed, 12 Apr 2000, Fred L. Drake, Jr. wrote:
> >  > Or do we need to separate out two categories of pragmas --
> >  > pre-parse and post-parse pragmas?
> >
> >   Eeeks!  We don't need too many special forms!  That's ugly!
> 
> Eek indeed.  I'm tempted to suggest we drop the multiple-encoding
> issue (i can hear the screams now).  But you're right, i've never
> heard of another language that can handle configurable encodings
> right in the source code.  Is it really necessary to tackle that here?

Yes.
 
> Gak, what do Japanese programmers do?  Has anyone seen any of that
> kind of source code?

It's not intended for use by Asian programmers, it must be
seen as a way to equally support all those different languages
and scripts for which Python provides codecs.

Note that Fred's argument is not far fetched: if you look
closely at the way the compiler works it seems that adding
a new keyword would indeed be the simplest solution.

If done right, we could add some nifty lookup optimizations
to the byte code compiler, e.g. a module might declare all
globals as being constant or have all could allow the compiler
to assume that all global lookups return constants allowing
it to cache them or even rewrite the byte code at run-time...

But the concepts are still not 100% right -- if we want to
add scope to pragmas, we ought to follow the usual Python
lookup scheme: locals, globals, built-ins. This would introduce
the need to pass locals and globals to all APIs compiling
Python source code.

-- 
Marc-Andre Lemburg
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