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Fri, 25 Sep 2020 15:15:57 +0200 (CEST) From: Markus Armbruster To: Cleber Rosa Subject: Re: [PATCH v2 28/38] qapi/gen.py: update write() to be more idiomatic References: <20200922210101.4081073-1-jsnow@redhat.com> <20200922210101.4081073-29-jsnow@redhat.com> <20200923152624.GO3312949@habkost.net> <20200924155959.GC191229@localhost.localdomain> Date: Fri, 25 Sep 2020 15:15:57 +0200 In-Reply-To: <20200924155959.GC191229@localhost.localdomain> (Cleber Rosa's message of "Thu, 24 Sep 2020 11:59:59 -0400") Message-ID: <87r1qqro8i.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=63.128.21.124; envelope-from=armbru@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: -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 , Eduardo Habkost , John Snow , Michael Roth , qemu-devel@nongnu.org, Alex =?utf-8?Q?Benn=C3=A9e?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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!