Macros in Python?

[Dominic]

Carl Banks wrote:
> Dominic wrote:
> 
>>
>>(defmacro with-root-privs (() &body body)
>>  (let ((oldidsym (gensym)))
>>    `(let ((,oldidsym (geteuid)))
>>       (seteuid 0)
>>       (unwind-protect
>>          (progn , at body)
>>        (seteuid ,oldidsym)))))
>>
>>Is there an easy way to produce similar code
>>in Python which gurantees that certain things
>>happen around some code? (Maybe by using
>>generators?)
>>
>>The normal approach would be to enclose everything
>>with try: finally: but this would scatter the
>>code all over.
> 
> 
> 
> It doesn't have to.  First, define:
> 
>     def get_root_privledges():
>         euid = os.geteuid()
>         os.seteuid(0)
>         return euid
> 
>     def release_root_privledges(euid):
>         os.seteuid(euid)
> 
> 
> Then you can do:
> 
>     old_euid = get_root_privledges()
>     try:
>         if x in user:
>             active.append(x)
>             ...
>     finally:
>         relase_root_privledges(old_euid)
> 
> 
> I hope this isn't what you consider "scattering the code all over."
> There is a certain niceness to the with macros (the ones that don't
> rebind any symbols, anyways), but try ... finally does the job just
> fine.
This solution is very straightforward but I have been curious wether
there is a "nicer" way to do the job. Alexander and Jp's postings
showed me that there are two very different approaches which could
also be used. Certainly all 3 solutions have their pros and cons
I'll consider all three.
So, thank you very much for all your answers :)

Ciao,
  Dominic

P.S. It would be nice to have a database for python usage patterns.


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