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Re: Append to python List

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Jussi Piitulainen於 2013年5月9日星期四UTC+8下午2時55分20秒寫道：
> RAHUL RAJ writes:
> 
> 
> 
> > Checkout the following code:
> 
> > 
> 
> > sample2 = [x+y for x in range(1,10) for y in range(1,10) if x!=y]   
> 
> > output=[]
> 
> > output=[x for x in sample2 if x not in output]
> 
> > 
> 
> > the output I get is
> 
> > 3 4 5 6 7 8 9 10 3 5 6 7 8 9 10 11 4 5 7 8 9 10 11 12 5 6 7 9 10 11
> 
> > 12 13 6 7 8 9 11 12 13 14 7 8 9 10 11 13 14 15 8 9 10 11 12 13 15 16
> 
> > 9 10 11 12 13 14 15 17 10 11 12 13 14 15 16 17
> 
> > 
> 
> > which contains duplicate values.
> 
> 
> 
> The second comprehension, [x for x in sample2 if x not in output], in
> 
> the context, is equivalent to [x for x in sample2 if x not in []]. It
> 
> does not refer to an incomplete version of the list that gets assigned
> 
> to the variable after it's done.

This is just the handy style for a non-critical loop.
In a critical loop, the number of  the total operation counts
does matter in the execution speed.

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Append to python List RAHUL RAJ <omrahulrajcse@gmail.com> - 2013-05-08 23:36 -0700
  Re: Append to python List Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2013-05-09 09:55 +0300
    Re: Append to python List 88888 Dihedral <dihedral88888@googlemail.com> - 2013-05-09 04:24 -0700
      Re: Append to python List Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2013-05-09 14:30 +0300
        Re: Append to python List 88888 Dihedral <dihedral88888@googlemail.com> - 2013-05-10 02:51 -0700
        Re: Append to python List Chris Angelico <rosuav@gmail.com> - 2013-05-09 21:49 +1000
          Re: Append to python List Anssi Saari <as@sci.fi> - 2013-05-11 18:47 +0300
            Re: Append to python List Chris Angelico <rosuav@gmail.com> - 2013-05-12 02:00 +1000
              Re: Append to python List 88888 Dihedral <dihedral88888@googlemail.com> - 2013-05-11 19:29 -0700
                Re: Append to python List Chris Angelico <rosuav@gmail.com> - 2013-05-12 12:40 +1000
          Re: Append to python List Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2013-05-12 09:02 +0300
  Re: Append to python List Chris Angelico <rosuav@gmail.com> - 2013-05-09 16:52 +1000
  Re: Append to python List Gary Herron <gary.herron@islandtraining.com> - 2013-05-08 23:54 -0700
    Re: Append to python List RAHUL RAJ <omrahulrajcse@gmail.com> - 2013-05-09 01:18 -0700
      Re: Append to python List RAHUL RAJ <omrahulrajcse@gmail.com> - 2013-05-09 01:19 -0700
      Re: Append to python List Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-05-09 11:14 +0000

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