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Re: New user's initial thoughts / criticisms of Python

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From Joshua Landau <joshua@landau.ws>
Date Mon, 11 Nov 2013 20:50:35 +0000
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Subject Re: New user's initial thoughts / criticisms of Python
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On 11 November 2013 10:39, Chris Angelico <rosuav@gmail.com> wrote:
> On Mon, Nov 11, 2013 at 9:09 PM,  <lorenzo.gatti@gmail.com> wrote:
>> Regarding the "select" statement, I think the most "Pythonic" approach is using dictionaries rather than nested ifs.
>> Supposing we want to decode abbreviated day names ("mon") to full names ("Monday"):
>
> You can't [normally], for instance, build up a
> dictionary that handles inequalities, but you can do that with elif.
> [...] Consider the following logic:
>
> A 'minor weapon' is based on a roll of a 100-sided dice. If it's 01 to
> 70, "+1 weapon: 2,000gp [weapon]"; if it's 71 to 85, "+2 weapon:
> 8,000gp [weapon]"; if 86 to 90, "Specific weapon [minor specific
> weapon]"; and if 91 to 100, "Special ability [minor special weapon]
> and roll again".
>
> My code to handle that starts out with this array:
>
> "minor weapon":({
>     70,"+1 weapon: 2,000gp [weapon]",
>     85,"+2 weapon: 8,000gp [weapon]",
>     90,"Specific weapon [minor specific weapon]",
>     100,"Special ability [minor special weapon] and roll again",
> }),
>
> (that's Pike; in Python it'd be a list, or maybe a tuple of tuples),
> and denormalizes it into a lookup table by creating 70 entries quoting
> the first string, 15 quoting the second, 5, and 10, respectively. So,
> with a bit of preprocessing, a lookup table (which in this case is an
> array (list), but could just as easily be a dict) can be used to
> handle inequalities.

The obvious way to me is a binary search:

    from bisect import bisect_left

    class FloorMap:
        def __init__(self, dct):
            self.indexes = sorted(list(dct))
            self.dct = dct

        def __getitem__(self, itm):
            index = self.indexes[bisect_left(self.indexes, itm)]
            return self.dct[index]


    minor_weapon = FloorMap({
        70:  "+1 weapon: 2,000gp [weapon]",
        85:  "+2 weapon: 8,000gp [weapon]",
        90:  "Specific weapon [minor specific weapon]",
        100: "Special ability [minor special weapon] and roll again"
    })

    minor_weapon[63]
    #>>> '+1 weapon: 2,000gp [weapon]'

The precise details of the wrapper class here are just to make
initialisation pretty; it could be done straight from a pair of lists
too:

    from bisect import bisect_left

    minor_weapon_indexes = 70, 85, 90, 100
    minor_weapon_descriptions = (
        "+1 weapon: 2,000gp [weapon]",
        "+2 weapon: 8,000gp [weapon]",
        "Specific weapon [minor specific weapon]",
        "Special ability [minor special weapon] and roll again"
    )

    minor_weapon_descriptions[bisect_left(minor_weapon_indexes, 80)]
    #>>> '+2 weapon: 8,000gp [weapon]'

Compare to

    if 80 <= 70:
        res = "+1 weapon: 2,000gp [weapon]"

    elif 80 <= 85:
        res = "+2 weapon: 8,000gp [weapon]"

    elif 80 <= 90:
        res = "Specific weapon [minor specific weapon]"

    elif 80 <= 100:
        res = "Special ability [minor special weapon] and roll again"

which although shorter¹ is a lot less data-driven and much less reusable.

¹ Longer if you ignore the import and class declaration.

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Thread

New user's initial thoughts / criticisms of Python John von Horn <j.h69@btinternet.com> - 2013-11-09 07:08 -0600
  Re: New user's initial thoughts / criticisms of Python Ned Batchelder <ned@nedbatchelder.com> - 2013-11-09 05:22 -0800
  Re: New user's initial thoughts / criticisms of Python Joshua Landau <joshua@landau.ws> - 2013-11-09 13:27 +0000
    Re: New user's initial thoughts / criticisms of Python Jonathan <jtcegh@gmail.com> - 2013-11-09 14:44 -0800
      Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-10 10:29 +1100
      Re: New user's initial thoughts / criticisms of Python MRAB <python@mrabarnett.plus.com> - 2013-11-10 00:50 +0000
      Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-10 11:54 +1100
      Re: New user's initial thoughts / criticisms of Python Neil Cerutti <neilc@norwich.edu> - 2013-11-11 15:30 +0000
    Re: New user's initial thoughts / criticisms of Python Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2013-11-10 13:24 +0100
  Re: New user's initial thoughts / criticisms of Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-11-09 13:41 +0000
  Re: New user's initial thoughts / criticisms of Python Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2013-11-09 16:24 +0200
  Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-10 01:27 +1100
    Sandboxing Python [was Re: New user's initial thoughts / criticisms of Python] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-11-09 15:25 +0000
      Re: Sandboxing Python [was Re: New user's initial thoughts / criticisms of Python] Chris Angelico <rosuav@gmail.com> - 2013-11-10 02:32 +1100
    Re: New user's initial thoughts / criticisms of Python Jorgen Grahn <grahn+nntp@snipabacken.se> - 2013-11-10 08:47 +0000
      Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-10 20:22 +1100
      Re: New user's initial thoughts / criticisms of Python Ian Kelly <ian.g.kelly@gmail.com> - 2013-11-10 04:39 -0700
      Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-10 22:43 +1100
      Re: New user's initial thoughts / criticisms of Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-11-10 12:12 -0500
      Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-11 10:29 +1100
      Re: New user's initial thoughts / criticisms of Python Terry Reedy <tjreedy@udel.edu> - 2013-11-10 19:13 -0500
  Re: New user's initial thoughts / criticisms of Python rusi <rustompmody@gmail.com> - 2013-11-09 07:38 -0800
    Re: New user's initial thoughts / criticisms of Python Roy Smith <roy@panix.com> - 2013-11-09 10:56 -0500
      Re: New user's initial thoughts / criticisms of Python rusi <rustompmody@gmail.com> - 2013-11-09 08:30 -0800
        Re: New user's initial thoughts / criticisms of Python Rick Johnson <rantingrickjohnson@gmail.com> - 2013-11-10 21:36 -0800
          Re: New user's initial thoughts / criticisms of Python Roy Smith <roy@panix.com> - 2013-11-11 09:01 -0500
            Re: New user's initial thoughts / criticisms of Python rusi <rustompmody@gmail.com> - 2013-11-11 07:14 -0800
            Re: New user's initial thoughts / criticisms of Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-11-11 21:05 -0500
            Re: New user's initial thoughts / criticisms of Python Ethan Furman <ethan@stoneleaf.us> - 2013-11-12 14:38 -0800
  Re: New user's initial thoughts / criticisms of Python John von Horn <j.h69@btinternet.com> - 2013-11-09 14:19 -0600
  Re: New user's initial thoughts / criticisms of Python Tim Chase <python.list@tim.thechases.com> - 2013-11-09 14:39 -0600
  Re: New user's initial thoughts / criticisms of Python Mark Janssen <dreamingforward@gmail.com> - 2013-11-09 12:33 -0800
    Re: New user's initial thoughts / criticisms of Python Ned Batchelder <ned@nedbatchelder.com> - 2013-11-09 12:54 -0800
      Re: New user's initial thoughts / criticisms of Python Mark Janssen <dreamingforward@gmail.com> - 2013-11-09 13:21 -0800
  Re: New user's initial thoughts / criticisms of Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-11-09 21:01 +0000
  Re: New user's initial thoughts / criticisms of Python Tim Chase <python.list@tim.thechases.com> - 2013-11-09 15:20 -0600
  Re: New user's initial thoughts / criticisms of Python lorenzo.gatti@gmail.com - 2013-11-11 02:09 -0800
    Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-11 21:39 +1100
      Re: New user's initial thoughts / criticisms of Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-11-11 11:17 +0000
        Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-11 22:32 +1100
        Re: New user's initial thoughts / criticisms of Python Mark Janssen <dreamingforward@gmail.com> - 2013-11-11 14:29 -0800
    Re: New user's initial thoughts / criticisms of Python Robert Kern <robert.kern@gmail.com> - 2013-11-11 11:53 +0000
    Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-11 23:07 +1100
    Re: New user's initial thoughts / criticisms of Python Joshua Landau <joshua@landau.ws> - 2013-11-11 20:50 +0000
    Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-12 09:21 +1100
    Re: New user's initial thoughts / criticisms of Python Joshua Landau <joshua@landau.ws> - 2013-11-12 01:53 +0000

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