Compiler directives in the source

[Chris Liechti]

Dale Strickland-Clark <dale at riverhall.NOTHANKS.co.uk> wrote in 
news:u4g24vs1ah54s0sqnbjc1o1c6bds3u6rm5 at 4ax.com:

> The earlier discussion on coding directives in comments got me
> thinking.
> 
> In case you missed it, the following two posts summarise it quite
> nicely for me:
> 
>>Paul Rubin <phr-n2003b at NOSPAMnightsong.com> wrote:
>>
>>>Brian Quinlan <brian at sweetapp.com> writes:
>>>> Just add:
>>>> # -*- coding: Latin-1 -*-
>>>> 
>>>> to the top of your source files and you will be fine.
>>>
>>>What is this nonsense?  The interpreter is reading comment text now?
>>>Yucch!
> 
> There is a general need for passing information to the compiler that
> hasn't been addressed by this horrible magic comment.
> 
> I think the following compiler options would be usefully avilable as
> directives in the source as well as on the command line:
> 
> -O     : optimize generated bytecode 
> -OO    : remove doc-strings in addition to the -O optimizations
> -Q arg : division options:
> -S     : don't imply 'import site' on initialization
> -v     : verbose (trace import statements) (also PYTHONVERBOSE=x)
> -W arg : warning control 
> -x     : skip first line of source
> 
> To that list, I would like to add:
> 
> debug arg : control value of __debug__ and assert() (independent of
>             optimisation)

absolutely! yes, i like that idea... i'd also add an option to disable 
".py?" file generation, not that important but nice for some apps whre that 
files are disturbing.
 
> Just about any non alpha-character in column 1 could be unambiguously
> applied as a signal character, with a few obvious exceptions
> including: #, (, [, tab and space. So what about % ?

but there is one drawback... it's not backwards compatible... a script that 
uses this feature would break when run in an older python interpreter.

> That would give us a set of compiler directives like these:
> 
> %optimize off | on | full
> %division old | warn |new
> %importsite off | on
> %verbose off | on
> %warnings arg
> %skip 1
> %debug off | on
> %ignorecase off | on     (like PYTHONCASEOK)
> %path dir;dir...         (like PYTHONPATH)
> %home dir                (like PYTHONHOME)

the last three are critical. they can be used to customize the environment 
and if it in the source file itself it a bit against its purpose ;-)

and where is "%encoding name" ;-)

> The skip option is a bit of a tease as the option would have to appear
> after the line to be skipped but much more useful than on the command
> line.
> 
> A rule that the first non-directive (excluding first line where "skip
> 1") marked the end of the directives would be acceptable and would
> simplify the handling.
> 
> Advantages: Flexible and easily extended. Easier to remember. Simple
> syntax. Comments stay as comments. 
> 
> Disadvantages: Too late? Bigger code change?

it'd be nice to set the optimization level within the file :-)

chris

-- 
Chris <cliechti at gmx.net>