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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]:60316 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kLnn3-0004e5-88 for qemu-devel@archiver.kernel.org; Fri, 25 Sep 2020 09:29:33 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:57286) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kLnjv-0001J8-7A for qemu-devel@nongnu.org; Fri, 25 Sep 2020 09:26:20 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:36791) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kLnjs-0006Dd-Hi for qemu-devel@nongnu.org; Fri, 25 Sep 2020 09:26:18 -0400 Dkim-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1601040375; 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: in-reply-to:in-reply-to:references:references; bh=4qXDpfOqFwEE9958o2P2pAyk6QjKlWM5xDpqBnqkFG0=; b=G28ptt7wwSguoIBBzxEecaUMd/+d1KNIeGbco73o8oKc+brjDdig2NzNE47LQanpvTKjZK E1TFOsFHTgMUJoRy7uBQzOiEp8/PMMBN9faby8fnrXtIedTexc86W5C2bXuFyI+sp7QqZZ OBK8HloQqtZ418bawp1exDi8IY9xjDw= 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-559-Xh3BtWQ4P9esi_xxSLogMw-1; Fri, 25 Sep 2020 09:26:10 -0400 X-MC-Unique: Xh3BtWQ4P9esi_xxSLogMw-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EF7AFAF208; Fri, 25 Sep 2020 13:26:08 +0000 (UTC) Received: from localhost (unknown [10.10.67.5]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9368B277DC; Fri, 25 Sep 2020 13:26:08 +0000 (UTC) Date: Fri, 25 Sep 2020 09:26:07 -0400 From: Eduardo Habkost To: Markus Armbruster Subject: Re: [PATCH v2 28/38] qapi/gen.py: update write() to be more idiomatic Message-ID: <20200925132607.GP3717385@habkost.net> 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> MIME-Version: 1.0 In-Reply-To: <87r1qqro8i.fsf@dusky.pond.sub.org> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=ehabkost@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=ehabkost@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/25 02:48:20 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -32 X-Spam_score: -3.3 X-Spam_bar: --- X-Spam_report: (-3.3 / 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, 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: Peter Maydell , John Snow , Michael Roth , qemu-devel@nongnu.org, Cleber Rosa , Alex =?utf-8?Q?Benn=C3=A9e?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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. -- Eduardo