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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]:44390 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kQY02-0004sk-VX for qemu-devel@archiver.kernel.org; Thu, 08 Oct 2020 11:38:34 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:54898) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kQXxQ-0003Cc-3U for qemu-devel@nongnu.org; Thu, 08 Oct 2020 11:35:52 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:44174) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kQXxM-0000Fz-UB for qemu-devel@nongnu.org; Thu, 08 Oct 2020 11:35:51 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1602171347; 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=aj78Hg5WX+au4jbKeZXF5XxH5K3aj2i/SjPxWAfD+60=; b=dlY0xWkduypznvJc35JaedFzVTGqtu526sfWmmxctUHbZkm9VqdC/1jAp5b4WiuFlK7U10 TQeQQAsYfLAjMbrkfiwQ0S1M6qEOkZf02D0ZVviIcxuO16DqCp15e+mGL1OdcII5mR7oHQ GEM4ngFVRq37YDn+adVtJiP09d6ZqL8= 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-217-lzo9Rj8yPXOfGhCD4UTJ1g-1; Thu, 08 Oct 2020 11:35:44 -0400 X-MC-Unique: lzo9Rj8yPXOfGhCD4UTJ1g-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8791F1054F8A for ; Thu, 8 Oct 2020 15:35:43 +0000 (UTC) Received: from [10.10.120.38] (ovpn-120-38.rdu2.redhat.com [10.10.120.38]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1A62860BFA; Thu, 8 Oct 2020 15:35:43 +0000 (UTC) Subject: Re: [PATCH v5 19/36] qapi/events.py: add type hint annotations To: Markus Armbruster References: <20201005195158.2348217-1-jsnow@redhat.com> <20201005195158.2348217-20-jsnow@redhat.com> <87zh4ye0fh.fsf@dusky.pond.sub.org> <87r1q92mi4.fsf@dusky.pond.sub.org> From: John Snow Message-ID: <1fd25ea2-50cb-a518-c105-498d5dd0978f@redhat.com> Date: Thu, 8 Oct 2020 11:35:42 -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: <87r1q92mi4.fsf@dusky.pond.sub.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 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=216.205.24.124; envelope-from=jsnow@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/08 02:56:27 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.214, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=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: Cleber Rosa , qemu-devel@nongnu.org, Eduardo Habkost Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 10/8/20 3:41 AM, Markus Armbruster wrote: > John Snow writes: > >> On 10/7/20 7:32 AM, Markus Armbruster wrote: >>> Ignorant question: what's the difference between -> None (like here) and >>> nothing (like __init__() above? >> >> This came up in Cleber's review, too. >> >> Mypy supports a gradual typing paradigm; it is designed to facilitate >> what we are doing here: the gradual adding of types until we are able >> to enforce static typing everywhere. >> >> To that end, mypy uses a simple heuristic to determine if a function >> is "typed" or "untyped": did you use any type annotations for it? >> >> Meanwhile, __init__ never returns anything. You do not need to >> annotate its return type. mypy knows what the return type is and must >> be. In the case of __init__ with no parameters, it is both untyped and >> strictly typed! >> >> Annotating the return type for no-parameter init methods convinces >> mypy that this is a strictly typed method. It doesn't do this >> automatically, because doing so might enable more checks than you were >> ready for simply because mypy was able to accurately surmise the >> typing of just __init__. >> >> So it's just a little flip switch to enable strict typing, really. >> >> --js >> >> https://mypy.readthedocs.io/en/stable/class_basics.html#annotating-init-methods > > I now understand we can omit -> None, except when it's the only type > hint, because omitting it then would make it untyped, which is not what > we want. > > Is this just for __init__(), or is it for any function that doesn't > return anything? > *just* __init__. Some other dunders have types that could be assumed, but aren't. I asked about this for some other well-known but hard-to-type dunders like __exit__ on the Typing-SIG list. Not a strong response yet, I might push again later. --js