PEP 340 contains several different ideas. This rewrite separates them into five major areas: - passing data into an iterator - finalising iterators - integrating finalisation into for loops - the new non-looping finalising statement - integrating all of these with generators.
The first area has nothing to do with finalisation, so it is not included in this rewrite (Steven Bethard wrote an Enhanced Iterators pre-PEP which covers only that area, though). The whole PEP draft can be found here: http://members.iinet.net.au/~ncoghlan/public/pep-3XX.html But I've inlined some examples that differ from or aren't in PEP 340 for those that don't have time to read the whole thing (example numbers are from the PEP): 4. A template that tries something up to n times:: def auto_retry(n=3, exc=Exception): for i in range(n): try: yield except exc, err: # perhaps log exception here yield raise # re-raise the exception we caught earlier Used as follows:: for del auto_retry(3, IOError): f = urllib.urlopen("http://python.org/";) print f.read() 6. It is easy to write a regular class with the semantics of example 1:: class locking: def __init__(self, lock): self.lock = lock def __enter__(self): self.lock.acquire() def __exit__(self, type, value=None, traceback=None): self.lock.release() if type is not None: raise type, value, traceback (This example is easily modified to implement the other examples; it shows that generators are not always the simplest way to do things.) 8. Find the first file with a specific header:: for name in filenames: stmt opening(name) as f: if f.read(2) == 0xFEB0: break 9. Find the first item you can handle, holding a lock for the entire loop, or just for each iteration:: stmt locking(lock): for item in items: if handle(item): break for item in items: stmt locking(lock): if handle(item): break 10. Hold a lock while inside a generator, but release it when returning control to the outer scope:: stmt locking(lock): for item in items: stmt unlocking(lock): yield item Cheers, Nick. -- Nick Coghlan | [EMAIL PROTECTED] | Brisbane, Australia --------------------------------------------------------------- http://boredomandlaziness.blogspot.com _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
