[Python-Dev] Merging PEP 310 and PEP 340-redux?

[Benji York]

I think this is my first post to python-dev, so a mini-intro: I've 
been lurking here for about 5 years, "professional" user a bit longer, 
now working at Zope Corp.

Guido van Rossum wrote:
> Going for all-out simplicity, I would like to be able to write these examples:
> 
> class locking:
>     def __init__(self, lock): self.lock = lock
>     def __enter__(self): self.lock.acquire()
>     def __exit__(self, *args): self.lock.release()
> 
> class opening:
>     def __init__(self, filename): self.filename = filename
>     def __enter__(self): self.f = open(self.filename); return self.f
>     def __exit__(self, *args): self.f.close()

I've read the entire discussion, but may have missed this point, so, 
correct me if I'm wrong. Wouldn't these semantics let "normal" objects 
be used in a do.  For example, if the file object had these methods:

def __enter__(self): return self
def __exit__(self, *args): self.close()

you could write

do file('whatever) as f:
     lines = f.readlines()

Or a lock:

def __enter__(self): self.aquire(); return self
def __exit__(self, *args): self.release()

do my_lock:
     a()
     b()
     c()
-- 
Benji York
Sr. Software Engineer
Zope Corporation