[Python-Dev] Pre-PEP: with syntax (was: New syntax threads -- summary wanted) (original) (raw)

M.-A. Lemburg mal@lemburg.com
Mon, 10 Feb 2003 12:34:48 +0100

Moore, Paul wrote:

PEP: XXXX Title: Syntax for Reliable Acquisition/Release Pairs Version: Revision:Revision: Revision: Last-Modified: Date:2002/08/2616:29:31Date: 2002/08/26 16:29:31 Date:2002/08/2616:29:31 Author: Michael Hudson <mwh@python.net>, Paul Moore <gustav@morpheus.demon.co.uk> Status: Draft Type: Standards Track Content-Type: text/plain Created: 18-Dec-2002 Python-Version: 2.4 Post-History:

Abstract It would be nice to have a less typing-intense way of writing: thelock.acquire() try: .... finally: thelock.release() This PEP proposes a piece of syntax (a 'with' block) and a "small-i" interface that generalizes the above.

-1

I don't see the gain from adding new syntax for this. It is rather likely that you want to do other cleanup stuff as well in the finally clause. With your new syntax this would become:

try: with mylock: ... finally: ... other cleanup code ...

The new syntax saves you one line and obscures the code rather than clarifying what is happening (who knows what mylock does in its enter/exit method ?).

The original argument for this was not to save you typing, it was built on the rather unlikely case where the process receives a signal or MemoryError causing an exception while executing the byte codes after calling .acquire() and before entering the try-block.

However, that's not hard to deal with either because all you need to do is place the .acquire() call inside the try-block and then adding a check whether you have to release the lock in the finally-clause.

-- Marc-Andre Lemburg eGenix.com

Professional Python Software directly from the Source (#1, Feb 10 2003)

Python/Zope Products & Consulting ... http://www.egenix.com/ mxODBC, mxDateTime, mxTextTools ... http://python.egenix.com/

Python UK 2003, Oxford: 50 days left EuroPython 2003, Charleroi, Belgium: 134 days left