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dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:59232 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kLqmm-0002up-3C for qemu-devel@archiver.kernel.org; Fri, 25 Sep 2020 12:41:28 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:50536) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kLqfM-0002vJ-E3 for qemu-devel@nongnu.org; Fri, 25 Sep 2020 12:33:49 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:27680) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kLqfK-0008Gm-Jr for qemu-devel@nongnu.org; Fri, 25 Sep 2020 12:33:48 -0400 Dkim-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1601051625; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=njVxwsFBl5qqvocgMMqfLHI/WZSPERi0+KklB2rnKQA=; b=LBGOjUHVazDsAQzGffw58EfJYvOsp4juvqlwH/IscKyZRVP0W0hMv0tEUBybaofAJzCg5U hntz780Zh32kegXQPUDeJ0ECPLZz3sb+ni4MKm16QrsKmyhtT1nMhnVnxfg2PgWU6Z8QUt 453RNrk9egp5rC3QFYzU7QqC9cHQkC4= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-506--1TbFKiIOZONdUwNEv13tw-1; Fri, 25 Sep 2020 12:33:42 -0400 X-MC-Unique: -1TbFKiIOZONdUwNEv13tw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 307A780734F; Fri, 25 Sep 2020 16:33:41 +0000 (UTC) Received: from [10.10.119.140] (ovpn-119-140.rdu2.redhat.com [10.10.119.140]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0E6BE5C1D7; Fri, 25 Sep 2020 16:33:37 +0000 (UTC) Subject: Re: [PATCH v2 28/38] qapi/gen.py: update write() to be more idiomatic To: Eduardo Habkost , Markus Armbruster References: <20200922210101.4081073-1-jsnow@redhat.com> <20200922210101.4081073-29-jsnow@redhat.com> <20200923152624.GO3312949@habkost.net> <20200924155959.GC191229@localhost.localdomain> <87r1qqro8i.fsf@dusky.pond.sub.org> <20200925132607.GP3717385@habkost.net> From: John Snow Message-ID: <73455868-86f9-e1a7-52e7-a61a8484a999@redhat.com> Date: Fri, 25 Sep 2020 12:33:37 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200925132607.GP3717385@habkost.net> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jsnow@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=jsnow@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/25 01:07:33 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.199, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.238, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Michael Roth , Peter Maydell , =?UTF-8?Q?Alex_Benn=c3=a9e?= , qemu-devel@nongnu.org, Cleber Rosa Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 9/25/20 9:26 AM, Eduardo Habkost wrote: > On Fri, Sep 25, 2020 at 03:15:57PM +0200, Markus Armbruster wrote: >> Cleber Rosa writes: >> >>> On Wed, Sep 23, 2020 at 02:37:27PM -0400, John Snow wrote: >>>> On 9/23/20 11:26 AM, Eduardo Habkost wrote: >>>>> On Tue, Sep 22, 2020 at 05:00:51PM -0400, John Snow wrote: >>>>>> Make the file handling here just a tiny bit more idiomatic. >>>>>> (I realize this is heavily subjective.) >>>>>> >>>>>> Use exist_ok=True for os.makedirs and remove the exception, >>>>>> use fdopen() to wrap the file descriptor in a File-like object, >>>>>> and use a context manager for managing the file pointer. >>>>>> >>>>>> Signed-off-by: John Snow >>>>> >>>>> Reviewed-by: Eduardo Habkost >>>>> >>>>> I really miss a comment below explaining why we use >>>>> open(os.open(pathname, ...), ...) instead of open(pathname, ...). >> >> This code: >> >> fd = os.open(pathname, os.O_RDWR | os.O_CREAT, 0o666) >> f = open(fd, 'r+', encoding='utf-8') >> >>>> Not known to me. It was introduced in 907b846653 as part of an effort to >>>> reduce rebuild times. Maybe this avoids a modification time change if the >>>> file already exists? >>>> >>>> Markus? >>> >>> AFACIT the change on 907b846653 is effective because of the "is new >>> text different from old text?" conditional. I can not see how the >>> separate/duplicate open/fdopen would contribute to that. >>> >>> But, let's hear from Markus. >> >> This was my best attempt to open the file read/write, creating it if it >> doesn't exist. >> >> Plain >> >> f = open(pathname, "r+", encoding='utf-8') >> >> fails instead of creates, and >> >> f = open(pathname, "w+", encoding='utf-8') >> >> truncates. >> >> If you know a better way, tell me! > > Thanks for the explanation! > > Yeah, it looks like there's no combination of open() flags that > would get translated to O_RDWR|O_CREAT. > > Using os.open() like you did seems more straightforward than > catching FileNotFoundError. > OK. Using fdopen works for us, so let's stick with it. I will add a comment explaining our reasoning. Thanks! --js