Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder1.news.weretis.net!news.albasani.net!feeder.erje.net!eu.feeder.erje.net!newsfeed.xs4all.nl!newsfeed4.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.000 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'else:': 0.03; '21,': 0.07; 'context': 0.07; 'finally:': 0.07; 'lawrence': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'subject:method': 0.09; 'try:': 0.09; 'api': 0.11; 'chained': 0.16; 'clauses.': 0.16; 'connect.': 0.16; 'corrupt': 0.16; 'lite': 0.16; 'oserror': 0.16; 'received:80.91.229.3': 0.16; 'received:dip0.t-ipconnect.de': 0.16; 'received:plane.gmane.org': 0.16; 'received:t-ipconnect.de': 0.16; 'exception': 0.16; 'sat,': 0.16; 'wrote:': 0.18; 'all,': 0.19; 'bit': 0.19; 'feb': 0.22; '>>>': 0.22; 'import': 0.22; 'header:User-Agent:1': 0.23; 'header:X-Complaints-To:1': 0.27; 'am,': 0.29; 'raise': 0.29; "i'm": 0.30; 'too.': 0.31; 'away.': 0.31; 'raised': 0.31; 'reduced': 0.31; 'way?': 0.31; 'file': 0.32; 'probably': 0.32; 'level.': 0.33; 'subject:the': 0.34; 'could': 0.34; 'subject:with': 0.35; 'connection': 0.35; 'except': 0.35; 'there': 0.35; 'being': 0.38; 'manager': 0.38; 'to:addr:python-list': 0.38; 'rather': 0.38; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'catch': 0.60; 'ian': 0.60; 'soon': 0.63; 'chance': 0.65; 'note:': 0.66; 'due': 0.66; 'close': 0.67; '2015': 0.84; 'needed:': 0.84; 'subject:try': 0.84 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Peter Otten <__peter__@web.de> Subject: Re: try pattern for database connection with the close method Date: Sat, 21 Feb 2015 16:27:17 +0100 Organization: None References: <6trfeate2ppvm1mcapgr0g4g2fd3vceab6@4ax.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7Bit X-Gmane-NNTP-Posting-Host: p57bd9545.dip0.t-ipconnect.de User-Agent: KNode/4.13.3 X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Newsgroups: comp.lang.python Message-ID: Lines: 52 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1424532607 news.xs4all.nl 2930 [2001:888:2000:d::a6]:56771 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:86048 Ian Kelly wrote: > On Sat, Feb 21, 2015 at 5:22 AM, Mark Lawrence > wrote: >> On 21/02/2015 02:42, Mario Figueiredo wrote: >>> >>> Hello all, >>> >>> I'm using the following pattern for db access that requires me to >>> close the connection as soon as it is not needed: >>> >>> import sqlite3 as lite >>> >>> try: >>> db = lite.connect('data.db') >>> except lite.DatabaseError: >>> raise OSError('database file corrupt or not found.') >>> else: >>> try: >>> with db: >>> db.execute(sql, parms) >>> except lite.IntegrityError: >>> raise ValueError('invalid data') >>> finally: >>> db.close() >>> >>> Since it's a bit verbose, is there a better way? >>> >>> Note: The user of this API has the whole database functionality >>> abstracted away. Hence the exception channeling in the except clauses. >>> >> >> Use your context manager at the outer level. >> >> import sqlite3 as lite >> >> try: >> with lite.connect('data.db') as db: >> try: >> db.execute(sql, parms) >> except lite.IntegrityError: >> raise ValueError('invalid data') >> except lite.DatabaseError: >> raise OSError('database file corrupt or not found.') > > This could result in the OSError being misleadingly raised due to some > DatabaseError raised by the execute rather than the connect. The OP probably wants to catch these DatabaseErrors, too. Also, the chance of a misleading traceback has been greatly reduced with the advent of chained exceptions.