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Re: True == 1 weirdness

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Subject Re: True == 1 weirdness
Date Wed, 16 Sep 2015 13:36:52 -0400
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On Wed, Sep 16, 2015, at 13:24, Steven D'Aprano wrote:
> On Thu, 17 Sep 2015 12:03 am, Random832 wrote:
>
> if word in line in text:
>     print("word in line and line in text")
> 
> But I agree with Tim Chase: I wouldn't use it, even though it's legal.

I just had another thought on *why* the other cases make me so uneasy.

The reason this is reasonable for simple cases like a > b > c or a < b
<= c is that, in their normal meanings, these operations are transitive.
a > b and b > c implies a > c. a < b and b <= c implies a < c. This is
also a good reason for allowing "==" or "is" anywhere - because it's a
natural way to write a graph including an equivalence class: a < b == c
< d implies b < d, a < c, and a < d. So it's a natural way of writing
it. On the other hand, a in b in c doesn't imply a in c for several
common cases, and a > b < c doesn't imply anything about the
relationship between a and c, so it really shouldn't be a single
expression.

A chained comparison doesn't *actually* compare non-adjacent elements,
but with well-defined transitive relationships (or... semi-transitive?
is there a word for this? My point being that when you include some ==
or mix <= and < together, it still allows you to make some statements
about their relationships), you are essentially saying "a, b, c are
ordered". The generalization to mixing arbitrary operators loses this
aspect.

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Thread

True == 1 weirdness "Blake T. Garretson" <blake.garretson@gmail.com> - 2015-09-16 05:16 -0700
  Re: True == 1 weirdness Jussi Piitulainen <harvesting@makes.email.invalid> - 2015-09-16 15:53 +0300
    Re: True == 1 weirdness Chris Angelico <rosuav@gmail.com> - 2015-09-16 23:05 +1000
    Re: True == 1 weirdness "Blake T. Garretson" <blake.garretson@gmail.com> - 2015-09-16 06:14 -0700
    Re: True == 1 weirdness Random832 <random832@fastmail.com> - 2015-09-16 10:03 -0400
      Re: True == 1 weirdness Steven D'Aprano <steve@pearwood.info> - 2015-09-17 03:24 +1000
        Re: True == 1 weirdness Random832 <random832@fastmail.com> - 2015-09-16 13:36 -0400
        Re: True == 1 weirdness "Sven R. Kunze" <srkunze@mail.de> - 2015-09-16 19:57 +0200
        Re: True == 1 weirdness Ian Kelly <ian.g.kelly@gmail.com> - 2015-09-16 11:57 -0600
    Re: True == 1 weirdness Chris Angelico <rosuav@gmail.com> - 2015-09-17 00:26 +1000
      Re: True == 1 weirdness Marko Rauhamaa <marko@pacujo.net> - 2015-09-16 19:16 +0300
        Re: True == 1 weirdness "Sven R. Kunze" <srkunze@mail.de> - 2015-09-16 18:37 +0200
          Re: True == 1 weirdness Marko Rauhamaa <marko@pacujo.net> - 2015-09-16 19:53 +0300
            Re: True == 1 weirdness Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-09-17 18:30 +1200
        Re: True == 1 weirdness Random832 <random832@fastmail.com> - 2015-09-16 12:57 -0400
          Re: True == 1 weirdness Steven D'Aprano <steve@pearwood.info> - 2015-09-17 03:39 +1000
            Re: True == 1 weirdness Marko Rauhamaa <marko@pacujo.net> - 2015-09-16 20:42 +0300
              Re: True == 1 weirdness Emile van Sebille <emile@fenx.com> - 2015-09-16 11:46 -0700
            Re: True == 1 weirdness Grant Edwards <invalid@invalid.invalid> - 2015-09-16 17:46 +0000
              Re: True == 1 weirdness "Sven R. Kunze" <srkunze@mail.de> - 2015-09-16 20:13 +0200
                Re: True == 1 weirdness Grant Edwards <invalid@invalid.invalid> - 2015-09-16 19:47 +0000
                Re: True == 1 weirdness Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-16 21:25 +0100
                Re: True == 1 weirdness Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-09-17 18:36 +1200
                Re: True == 1 weirdness "Sven R. Kunze" <srkunze@mail.de> - 2015-09-16 23:05 +0200
                Re: True == 1 weirdness Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-09-17 18:39 +1200
                Re: True == 1 weirdness "Sven R. Kunze" <srkunze@mail.de> - 2015-09-17 22:46 +0200
                Re: True == 1 weirdness Tim Chase <python.list@tim.thechases.com> - 2015-09-17 16:26 -0500
                Re: True == 1 weirdness "Sven R. Kunze" <srkunze@mail.de> - 2015-09-17 23:52 +0200
                Re: True == 1 weirdness Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-16 22:30 +0100
                Re: True == 1 weirdness "Sven R. Kunze" <srkunze@mail.de> - 2015-09-17 00:15 +0200
                Re: True == 1 weirdness Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-17 01:06 +0100
                Re: True == 1 weirdness Steven D'Aprano <steve@pearwood.info> - 2015-09-17 11:33 +1000
                Re: True == 1 weirdness Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-17 10:56 +0100
                Re: True == 1 weirdness alister <alister.nospam.ware@ntlworld.com> - 2015-09-17 12:07 +0000
                Re: True == 1 weirdness Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-17 13:27 +0100
                Re: True == 1 weirdness Steven D'Aprano <steve@pearwood.info> - 2015-09-17 12:34 +1000
                Re: True == 1 weirdness Chris Angelico <rosuav@gmail.com> - 2015-09-17 10:53 +1000
                Re: True == 1 weirdness Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-09-17 18:42 +1200
                Re: True == 1 weirdness Emile van Sebille <emile@fenx.com> - 2015-09-16 18:12 -0700
                Re: True == 1 weirdness Tim Chase <python.list@tim.thechases.com> - 2015-09-16 18:10 -0500
            Re: True == 1 weirdness "Sven R. Kunze" <srkunze@mail.de> - 2015-09-16 19:53 +0200
              Re: True == 1 weirdness Marko Rauhamaa <marko@pacujo.net> - 2015-09-16 22:47 +0300
            Re: True == 1 weirdness Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-16 21:29 +0100
            Re: True == 1 weirdness Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-16 22:27 +0100
        Re: True == 1 weirdness "Sven R. Kunze" <srkunze@mail.de> - 2015-09-16 19:23 +0200
          Re: True == 1 weirdness Grant Edwards <invalid@invalid.invalid> - 2015-09-16 17:27 +0000
            Re: True == 1 weirdness Emile van Sebille <emile@fenx.com> - 2015-09-16 10:41 -0700
            Re: True == 1 weirdness Steven D'Aprano <steve@pearwood.info> - 2015-09-17 03:42 +1000
              Re: True == 1 weirdness Grant Edwards <invalid@invalid.invalid> - 2015-09-16 17:44 +0000
                Re: True == 1 weirdness Random832 <random832@fastmail.com> - 2015-09-16 13:55 -0400
                Re: True == 1 weirdness Ian Kelly <ian.g.kelly@gmail.com> - 2015-09-16 11:55 -0600
                Re: True == 1 weirdness Steven D'Aprano <steve@pearwood.info> - 2015-09-17 11:16 +1000
            Re: True == 1 weirdness Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-16 21:22 +0100
        Re: True == 1 weirdness Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-16 21:17 +0100
      Re: True == 1 weirdness Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-09-17 18:24 +1200
        Re: True == 1 weirdness Jussi Piitulainen <harvesting@makes.email.invalid> - 2015-09-17 10:06 +0300
          Re: True == 1 weirdness Ian Kelly <ian.g.kelly@gmail.com> - 2015-09-17 12:49 -0600
            Re: True == 1 weirdness Jussi Piitulainen <harvesting@makes.email.invalid> - 2015-09-17 23:24 +0300
              Re: True == 1 weirdness Random832 <random832@fastmail.com> - 2015-09-17 17:26 -0400
                Re: True == 1 weirdness Marko Rauhamaa <marko@pacujo.net> - 2015-09-18 00:38 +0300
                Re: True == 1 weirdness "Sven R. Kunze" <srkunze@mail.de> - 2015-09-17 23:49 +0200
                Re: True == 1 weirdness Chris Angelico <rosuav@gmail.com> - 2015-09-18 12:03 +1000
                Re: True == 1 weirdness Jussi Piitulainen <harvesting@makes.email.invalid> - 2015-09-18 10:10 +0300
                Re: True == 1 weirdness Steven D'Aprano <steve@pearwood.info> - 2015-09-18 22:30 +1000
          Re: True == 1 weirdness Chris Angelico <rosuav@gmail.com> - 2015-09-18 04:57 +1000
            Re: True == 1 weirdness Jussi Piitulainen <harvesting@makes.email.invalid> - 2015-09-17 23:44 +0300
    Re: True == 1 weirdness Tim Chase <python.list@tim.thechases.com> - 2015-09-16 09:38 -0500
    Re: True == 1 weirdness Random832 <random832@fastmail.com> - 2015-09-16 11:40 -0400
      Re: True == 1 weirdness Steven D'Aprano <steve@pearwood.info> - 2015-09-17 03:33 +1000
        Re: True == 1 weirdness "Sven R. Kunze" <srkunze@mail.de> - 2015-09-16 19:41 +0200
          Re: True == 1 weirdness Steven D'Aprano <steve@pearwood.info> - 2015-09-17 11:22 +1000
        Re: True == 1 weirdness Random832 <random832@fastmail.com> - 2015-09-16 13:47 -0400
          Re: True == 1 weirdness Grant Edwards <invalid@invalid.invalid> - 2015-09-16 17:52 +0000
          Re: True == 1 weirdness Steven D'Aprano <steve@pearwood.info> - 2015-09-17 11:25 +1000
            Re: True == 1 weirdness Random832 <random832@fastmail.com> - 2015-09-17 02:10 -0400
              Re: True == 1 weirdness Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-09-17 12:29 +0000
        Re: True == 1 weirdness Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-16 21:38 +0100
        Re: True == 1 weirdness Random832 <random832@fastmail.com> - 2015-09-16 16:55 -0400
        Re: True == 1 weirdness "Sven R. Kunze" <srkunze@mail.de> - 2015-09-16 23:03 +0200
    Re: True == 1 weirdness jmp <jeanmichel@sequans.com> - 2015-09-21 14:01 +0200
  Re: True == 1 weirdness jmp <jeanmichel@sequans.com> - 2015-09-16 15:08 +0200
    Re: True == 1 weirdness "Blake T. Garretson" <blake.garretson@gmail.com> - 2015-09-16 06:17 -0700
  Re: True == 1 weirdness Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-09-16 09:28 -0400
  Re: True == 1 weirdness Chris Angelico <rosuav@gmail.com> - 2015-09-17 00:57 +1000

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