Re: None in string => TypeError?

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Date	Tue, 10 Jun 2014 02:31:54 +1000
Subject	Re: None in string => TypeError?
From	Chris Angelico <rosuav@gmail.com>
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On Tue, Jun 10, 2014 at 2:14 AM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
>> This is very Pythonic, Python is strictly typed language. There's no way
>> None could possibly be "inside" a string,
>
> Then `None in some_string` could immediately return False, instead of
> raising an exception.

Note, by the way, that CPython does have some optimizations that
immediately return False. If you ask if a 16-bit string is in an 8-bit
string, eg "\u1234" in "asdf", it knows instantly that it cannot
possibly be, and it just returns false. The "None in string" check is
different, and deliberately so.

I do prefer the thrown error. Some things make absolutely no sense,
and even if it's technically valid to say "No, the integer 61 is not
in the string 'asdf'", it's likely to be helpful to someone who thinks
that characters and integers are equivalent. You'll get an exception
immediately, instead of trying to figure out why it's returning False.

ChrisA

Thread

None in string => TypeError? Roy Smith <roy@panix.com> - 2014-06-09 08:34 -0700
  Re: None in string => TypeError? Ryan Hiebert <ryan@ryanhiebert.com> - 2014-06-09 10:42 -0500
  Re: None in string => TypeError? Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-09 09:50 -0600
  Re: None in string => TypeError? Paul Sokolovsky <pmiscml@gmail.com> - 2014-06-09 18:57 +0300
    Re: None in string => TypeError? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-06-09 16:14 +0000
      Re: None in string => TypeError? Chris Angelico <rosuav@gmail.com> - 2014-06-10 02:31 +1000
  Re: None in string => TypeError? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-06-09 16:07 +0000
  Re: None in string => TypeError? MRAB <python@mrabarnett.plus.com> - 2014-06-09 17:06 +0100
  Re: None in string => TypeError? Shiyao Ma <i@introo.me> - 2014-06-10 00:13 +0800
  Re: None in string => TypeError? Roy Smith <roy@panix.com> - 2014-06-09 12:53 -0400
  Re: None in string => TypeError? Chris Angelico <rosuav@gmail.com> - 2014-06-10 02:59 +1000
  Re: None in string => TypeError? Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-09 11:22 -0600
  Re: None in string => TypeError? Chris Angelico <rosuav@gmail.com> - 2014-06-10 03:40 +1000
  Re: None in string => TypeError? Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-09 11:58 -0600
  Re: None in string => TypeError? Chris Angelico <rosuav@gmail.com> - 2014-06-10 04:02 +1000

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