odd behavior

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  • Greg
    #1

    odd behavior

    Forgive me, and be kind, as I am just a newby learning this language
    out of M.L. Hetland's book. The following behavior of 2.4.1 seems very
    strange[color=blue][color=green][color=darkred]
    >>> x = ['aardvark', 'abalone', 'acme', 'add',[/color][/color][/color]
    'aerate'][color=blue][color=green][color=darkred]
    >>> x.sort(key=len)
    >>> x[/color][/color][/color]
    ['add', 'acme', 'aerate', 'abalone', 'aardvark'][color=blue][color=green][color=darkred]
    >>> x.sort(reverse= True)
    >>> x[/color][/color][/color]
    ['aerate', 'add', 'acme', 'abalone', 'aardvark']
    The function called on line 4, at least to me, should work on x as it
    was on line 3, not the previously existing x on line 1. What gives?
    By the way these functions do not exist in 2.3.5 so they must be newly
    implemented.

    Tags: None
    • Kristian Zoerhoff
      #2
      Re: odd behavior

      On 11 Nov 2005 11:34:47 -0800, Greg <gstgeorge@gmai l.com> wrote:[color=blue]
      > Forgive me, and be kind, as I am just a newby learning this language
      > out of M.L. Hetland's book. The following behavior of 2.4.1 seems very
      > strange[color=green][color=darkred]
      > >>> x = ['aardvark', 'abalone', 'acme', 'add',[/color][/color]
      > 'aerate'][color=green][color=darkred]
      > >>> x.sort(key=len)
      > >>> x[/color][/color]
      > ['add', 'acme', 'aerate', 'abalone', 'aardvark'][color=green][color=darkred]
      > >>> x.sort(reverse= True)
      > >>> x[/color][/color]
      > ['aerate', 'add', 'acme', 'abalone', 'aardvark']
      > The function called on line 4, at least to me, should work on x as it
      > was on line 3, not the previously existing x on line 1. What gives?[/color]

      The key option defaults to an alphabetic sort *every time* you call
      sort, so if you want to change this, you must call for your sort key
      each time. To do what you want, roll the sorts into one step:
      [color=blue][color=green][color=darkred]
      >>> x.sort(key=len, reverse=True)
      >>> x[/color][/color][/color]
      ['aardvark', 'abalone', 'aerate', 'acme', 'add']


      --
      Kristian

      kristian.zoerho ff(AT)gmail.com
      zoerhoff(AT)fre eshell.org

        Comment

        • Lee Harr
          #3
          Re: odd behavior

          On 2005-11-11, Kristian Zoerhoff <kristian.zoerh off@gmail.com> wrote:[color=blue]
          > On 11 Nov 2005 11:34:47 -0800, Greg <gstgeorge@gmai l.com> wrote:[color=green]
          >> Forgive me, and be kind, as I am just a newby learning this language
          >> out of M.L. Hetland's book. The following behavior of 2.4.1 seems very
          >> strange[color=darkred]
          >> >>> x = ['aardvark', 'abalone', 'acme', 'add',[/color]
          >> 'aerate'][color=darkred]
          >> >>> x.sort(key=len)
          >> >>> x[/color]
          >> ['add', 'acme', 'aerate', 'abalone', 'aardvark'][color=darkred]
          >> >>> x.sort(reverse= True)
          >> >>> x[/color]
          >> ['aerate', 'add', 'acme', 'abalone', 'aardvark']
          >> The function called on line 4, at least to me, should work on x as it
          >> was on line 3, not the previously existing x on line 1. What gives?[/color]
          >
          > The key option defaults to an alphabetic sort *every time* you call
          > sort, so if you want to change this, you must call for your sort key
          > each time. To do what you want, roll the sorts into one step:
          >[color=green][color=darkred]
          >>>> x.sort(key=len, reverse=True)
          >>>> x[/color][/color]
          > ['aardvark', 'abalone', 'aerate', 'acme', 'add']
          >
          >[/color]


          .... or just reverse it after:
          [color=blue][color=green][color=darkred]
          >>> x.sort(key=len)
          >>> x.reverse()
          >>> x[/color][/color][/color]
          ['aardvark', 'abalone', 'aerate', 'acme', 'add']

            Comment

            • Steven D'Aprano
              #4
              Re: odd behavior

              On Fri, 11 Nov 2005 11:34:47 -0800, Greg wrote:
              [color=blue]
              > Forgive me, and be kind, as I am just a newby learning this language
              > out of M.L. Hetland's book. The following behavior of 2.4.1 seems very
              > strange[/color]
              [color=blue][color=green][color=darkred]
              >>>> x = ['aardvark', 'abalone', 'acme', 'add', 'aerate']
              >>>> x.sort(key=len)
              >>>> x[/color][/color]
              > ['add', 'acme', 'aerate', 'abalone', 'aardvark'][color=green][color=darkred]
              >>>> x.sort(reverse= True)
              >>>> x[/color][/color]
              > ['aerate', 'add', 'acme', 'abalone', 'aardvark'][/color]
              [color=blue]
              > The function called on line 4, at least to me, should work on x as it
              > was on line 3, not the previously existing x on line 1. What gives?[/color]

              Why do you think it isn't operating on x as it is? The second sort is
              sorting in reverse lexicographic order, which is the result you get.

              I'm not running Python 2.4 so I can't test this, but to get the result you
              want I guess you want this:

              py> x.sort(key=len, reverse=True)
              py> x
              ['aardvark', 'abalone', 'aerate', 'acme', 'add']

              or:

              py> x.sort(key=len)
              py> x.reverse()


              --
              Steven.

                Comment

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