RE: checking if a list is empty

From	"Prasad, Ramit" <ramit.prasad@jpmchase.com>
Date	2011-05-11 13:39 -0400
Subject	RE: checking if a list is empty
References	<mailman.1226.1304663814.9059.python-list@python.org> <200e93c2-6b87-4113-9c6f-85815e51ea77@28g2000yqu.googlegroups.com> <4dc4b3c5$0$29991$c3e8da3$5496439d@news.astraweb.com> <iuvp98-446.ln1@svn.schaathun.net> <4dca7db5$0$29980$c3e8da3$5496439d@news.astraweb.com>
Newsgroups	comp.lang.python
Message-ID	<mailman.1416.1305135608.9059.python-list@python.org> (permalink)

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> I don't mean to insult anyone, but I've heard and read all the arguments against Python's truth-testing, and they
>don't impress me in the slightest. Most of them strike me as silly. The only argument that carries any weight to me is
>one which I haven't seen anyone raise:

>"if x:" turns something which arguably could have been a mistake ("oops, I forgot to write the condition!") into valid
>code.

The only problem I have had with the "if x:" notation is when I have values that might be empty lists, empty strings, None, or a boolean value being returned from the same source. But this is probably an instance when a good programmer would explicitly check the type instead of the naive "if x:" notation.

On the other hand, as a fairly n00b Python (and n00b Perl) developer, I find the notation "if not x:" to be far more English readable than "if x==None or len(x)== 0 or x==0 or bool(x):" (or some derivative/combination of those). 



Ramit

Ramit Prasad | JPMorgan Chase Investment Bank | Currencies Technology
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Thread

checking if a list is empty Jabba Laci <jabba.laci@gmail.com> - 2011-05-06 02:36 -0400
  Re: checking if a list is empty Richard Thomas <chardster@gmail.com> - 2011-05-06 03:34 -0700
  Re: checking if a list is empty scattered <tooscattered@gmail.com> - 2011-05-06 14:57 -0700
    Re: checking if a list is empty Philip Semanchuk <philip@semanchuk.com> - 2011-05-06 18:21 -0400
    Re: checking if a list is empty Ian Kelly <ian.g.kelly@gmail.com> - 2011-05-06 17:51 -0600
      Re: checking if a list is empty Jon Clements <joncle@googlemail.com> - 2011-05-06 17:43 -0700
        Re: checking if a list is empty Hans Mulder <hansmu@xs4all.nl> - 2011-05-14 10:52 +0200
    Re: checking if a list is empty Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-07 02:51 +0000
      Re: checking if a list is empty Hans Georg Schaathun <hg@schaathun.net> - 2011-05-11 10:02 +0100
        Re: checking if a list is empty Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-11 12:14 +0000
          Re: checking if a list is empty Hans Georg Schaathun <hg@schaathun.net> - 2011-05-11 15:05 +0100
            Re: checking if a list is empty "D'Arcy J.M. Cain" <darcy@druid.net> - 2011-05-11 10:27 -0400
              Re: checking if a list is empty Hans Georg Schaathun <hg@schaathun.net> - 2011-05-11 18:59 +0100
                Re: checking if a list is empty alex23 <wuwei23@gmail.com> - 2011-05-11 20:16 -0700
                Re: checking if a list is empty Hans Georg Schaathun <hg@schaathun.net> - 2011-05-12 06:20 +0100
            Re: checking if a list is empty Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-11 15:50 +0000
              Re: checking if a list is empty Chris Angelico <rosuav@gmail.com> - 2011-05-12 02:05 +1000
                Re: checking if a list is empty Hans Georg Schaathun <hg@schaathun.net> - 2011-05-11 18:56 +0100
                Re: checking if a list is empty harrismh777 <harrismh777@charter.net> - 2011-05-11 16:13 -0500
          RE: checking if a list is empty "Prasad, Ramit" <ramit.prasad@jpmchase.com> - 2011-05-11 13:39 -0400
        Re: checking if a list is empty Roy Smith <roy@panix.com> - 2011-05-11 08:26 -0400
          Re: checking if a list is empty Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-11 13:29 +0000
          Re: checking if a list is empty Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2011-05-12 17:44 +1200
            Re: checking if a list is empty Hans Georg Schaathun <hg@schaathun.net> - 2011-05-12 07:06 +0100
            Re: checking if a list is empty Roy Smith <roy@panix.com> - 2011-05-12 07:36 -0400
              Re: checking if a list is empty Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-13 00:16 +0000
                Re: checking if a list is empty rusi <rustompmody@gmail.com> - 2011-05-12 23:46 -0700
                Re: checking if a list is empty Chris Rebert <clp2@rebertia.com> - 2011-05-13 01:02 -0700
                Re: checking if a list is empty rusi <rustompmody@gmail.com> - 2011-05-13 03:58 -0700
                Re: checking if a list is empty Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2011-05-14 14:34 +1200
                Re: checking if a list is empty David Robinow <drobinow@gmail.com> - 2011-05-14 10:28 -0400
                Re: checking if a list is empty Roy Smith <roy@panix.com> - 2011-05-14 11:04 -0400
                Re: checking if a list is empty Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-14 07:39 +0000
                Re: checking if a list is empty rusi <rustompmody@gmail.com> - 2011-05-14 00:45 -0700
                Re: checking if a list is empty Chris Angelico <rosuav@gmail.com> - 2011-05-14 23:42 +1000
                Re: checking if a list is empty rusi <rustompmody@gmail.com> - 2011-05-14 08:47 -0700
                Re: checking if a list is empty Chris Angelico <rosuav@gmail.com> - 2011-05-15 01:55 +1000
                Re: checking if a list is empty rusi <rustompmody@gmail.com> - 2011-05-14 10:43 -0700
                Re: checking if a list is empty Terry Reedy <tjreedy@udel.edu> - 2011-05-14 17:29 -0400
                Re: checking if a list is empty Ben Finney <ben+python@benfinney.id.au> - 2011-05-15 09:26 +1000
                Re: checking if a list is empty rusi <rustompmody@gmail.com> - 2011-05-14 19:41 -0700
                Re: checking if a list is empty Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-15 05:07 +0000
                Re: checking if a list is empty rusi <rustompmody@gmail.com> - 2011-05-15 10:33 -0700
                Re: checking if a list is empty Terry Reedy <tjreedy@udel.edu> - 2011-05-15 17:36 -0400
                Re: checking if a list is empty rusi <rustompmody@gmail.com> - 2011-05-15 22:56 -0700
                Re: checking if a list is empty Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-16 00:36 +0000
                Re: checking if a list is empty harrismh777 <harrismh777@charter.net> - 2011-05-15 20:59 -0500
                Re: checking if a list is empty rusi <rustompmody@gmail.com> - 2011-05-15 22:40 -0700
                Re: checking if a list is empty harrismh777 <harrismh777@charter.net> - 2011-05-15 20:25 -0500
                Re: checking if a list is empty Terry Reedy <tjreedy@udel.edu> - 2011-05-15 21:57 -0400
                Re: checking if a list is empty Terry Reedy <tjreedy@udel.edu> - 2011-05-14 16:59 -0400
                Re: checking if a list is empty Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-15 05:00 +0000
                Re: checking if a list is empty Terry Reedy <tjreedy@udel.edu> - 2011-05-14 16:53 -0400
          Re: checking if a list is empty Terry Reedy <tjreedy@udel.edu> - 2011-05-12 15:37 -0400
          Re: checking if a list is empty Terry Reedy <tjreedy@udel.edu> - 2011-05-12 18:00 -0400
  Re: checking if a list is empty Raymond Hettinger <python@rcn.com> - 2011-05-06 15:52 -0700

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