Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!goblin1!goblin2!goblin.stu.neva.ru!newsfeed.xs4all.nl!newsfeed1.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!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 0.017 X-Spam-Evidence: '*H*': 0.97; '*S*': 0.00; 'syntax': 0.04; 'exception.': 0.09; 'raises': 0.09; 'satisfy': 0.09; 'try:': 0.09; 'url:github': 0.09; 'python': 0.11; 'def': 0.12; 'elsewhere,': 0.16; 'feasible': 0.16; 'indexerror:': 0.16; 'subject:pass': 0.16; 'exception': 0.16; 'all,': 0.19; 'example': 0.22; 'otherwise,': 0.22; 'this?': 0.23; 'case.': 0.24; 'propose': 0.24; 'pass': 0.26; 'subject:/': 0.26; 'code:': 0.26; 'generally': 0.29; 'raise': 0.29; 'converting': 0.30; 'skip:@ 10': 0.30; 'message- id:@mail.gmail.com': 0.30; 'code': 0.31; 'relies': 0.31; 'there.': 0.32; 'cases': 0.33; 'not.': 0.33; 'could': 0.34; 'problem': 0.35; 'except': 0.35; 'but': 0.35; 'received:google.com': 0.35; 'there': 0.35; 'object,': 0.36; 'list': 0.37; 'being': 0.38; 'sometimes': 0.38; 'thank': 0.38; 'version,': 0.38; 'to:addr:python-list': 0.38; 'short': 0.38; 'help,': 0.39; 'to:addr:python.org': 0.39; 'either': 0.39; 'url:about': 0.61; 'profile': 0.61; 'simple': 0.61; 'times': 0.62; 'such': 0.63; 'skip:n 10': 0.64; 'more': 0.64; 'here': 0.66; 'url:me': 0.69; 'abc': 0.84; 'subject:try': 0.84 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:date:message-id:subject:from:to:content-type; bh=jGS0WoroCTHHKBjTuLEGBXXzhd1rhTIc6uqfMYbB3sY=; b=BBUQnlu6L+/Yk56CMY3rtSzn1bSBA/hTa7KqTAiO2mzyLi2T2r563XWfH+F08eAkRq 0k4tNWkeETO51SiWi01eU2eXH5bNirq7ezw75w7i4aP8otMccxclTAcF0GvvsJhHRxlj ucE44xbpWf+Zf9dj+R7hoTir+eRfg7OxZ7XEvjrR3/bFy+9Zv3m1AzxiQNr+uLLCeenD n1xQM5Em+vSwgz/doQV7ECXRxlSNV8G3xZunVmb1JO6e/O5jJ3oUHAhx8ygrCvI85vg2 tEbjjxqOE6d0TcWNux4U5cstxwclYYS54Uo82GuDEhFAU34xNyCAajX0ASAb7HkcDgh8 RkBw== MIME-Version: 1.0 X-Received: by 10.182.98.168 with SMTP id ej8mr4817999obb.41.1413295715005; Tue, 14 Oct 2014 07:08:35 -0700 (PDT) Date: Tue, 14 Oct 2014 16:08:34 +0200 Subject: Short syntax for try/pass From: Leonardo Giordani To: python-list@python.org Content-Type: multipart/alternative; boundary=047d7b2e46f20e3d3b0505628d62 X-Mailman-Approved-At: Tue, 14 Oct 2014 16:09:02 +0200 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: 101 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1413295744 news.xs4all.nl 2911 [2001:888:2000:d::a6]:36410 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:79096 --047d7b2e46f20e3d3b0505628d62 Content-Type: text/plain; charset=UTF-8 Hi all, a lot of times the following pattern pops out in Python code: try: somecode except SomeException: pass A very simple example could be if you want to process a list that may be empty def process_list(lst): try: lst[0] = lst[0] + 1 except IndexError: pass or in more complex cases in which however an exception just signals that there is nothing to do there. Converting the code to a non-EAFP version, for example if len(lst) != 0: lst[0] = lst[0] + 1 is in my opinion generally against the Python nature, since it relies on a specific check on the object, instead of trusting the object as being able to either satisfy the request or raise an exception. That is, this solution is non-polymorphic. In such cases sometimes ABC may help, but generally speaking they it is not always the case of being an instance of a given ABC or not. The problem here is if the code raises an exception or not. Would it be feasible to propose a short syntax like this? pass SomeException: somecode where the above example would become: pass IndexError: lst[0] = lst[0] + 1 I could not find if such a syntax has been already discussed elsewhere, so please let me know if this is the case. Otherwise, what do you think about it? Thank you Leonardo Leonardo Giordani @tw_lgiordani - lgiordani.com My profile on About.me - My GitHub page --047d7b2e46f20e3d3b0505628d62 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Hi all,<= br>
a lot of times the following pattern pops out in Python code:<= br>
try:
=C2=A0somecode
except SomeException:
=C2=A0pass

A very simple example could be if= you want to process a list that may be empty

def proces= s_list(lst):
=C2=A0try:
=C2=A0 lst[0] =3D lst[0] + 1
<= /div>=C2=A0except IndexError:
=C2=A0 pass
<= div>

or in more complex cases in whi= ch however an exception just signals that there is nothing to do there.
=
Converting the code to a non-EAFP version, for example
if len(lst) !=3D 0:
=C2=A0lst[0] =3D lst[0] + 1

is in my opinion generally against the Python nature, since it relie= s on a specific check on the object, instead of trusting the object as bein= g able to either satisfy the request or raise an exception. That is, this s= olution is non-polymorphic.

In such cases sometimes ABC may help, bu= t generally speaking they it is not always the case of being an instance of= a given ABC or not. The problem here is if the code raises an exception or= not.

Would it be feasible to propose a short = syntax like this?

pass SomeException:
=C2=A0 somecode<= /div>

where the above example would become:

pass IndexError:
=C2=A0lst[0] =3D lst[0] + 1

<= div>I could not find if such a syntax has been already discussed elsewhere,= so please let me know if this is the case.

Otherwise, what do you t= hink about it?

Thank you

Leonardo



Leonardo Giordani
@tw_lgiordani - lgiordani.com
My profile on About.me - My GitHub page
--047d7b2e46f20e3d3b0505628d62--