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Re: list reversal error

Path csiph.com!feeder.erje.net!2.us.feeder.erje.net!bloom-beacon.mit.edu!bloom-beacon.mit.edu!panix!gordon
From John Gordon <gordon@panix.com>
Newsgroups comp.lang.python
Subject Re: list reversal error
Date Thu, 3 Mar 2016 23:08:15 +0000 (UTC)
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In <8b3d06eb-0027-4396-bdf8-fee0cc9ff771@googlegroups.com> vlyamtsev@gmail.com writes:

> i have list of strings "data" and i am trying to build reverse list data1
> data1 = []
> for i in range(len(data)):
>    j = len(data) - i
>    data1.append(data[j])

> but i have the following error:
> data1.append(data[j])
> IndexError: list index out of range
>  
> am i doing it wrong?
> Thanks

Python lists are zero-indexed, meaning a list of five items will have
indexes 0 to 4.

The first time through your loop, i is 0, so

    j = len(data) - i 

evaluates to

    j = len(data)

which would yield 5 for a five-element list, but the last actual element
is in data[4].

-- 
John Gordon                   A is for Amy, who fell down the stairs
gordon@panix.com              B is for Basil, assaulted by bears
                                -- Edward Gorey, "The Gashlycrumb Tinies"

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Thread

list reversal error vlyamtsev@gmail.com - 2016-03-03 14:51 -0800
  Re: list reversal error John Gordon <gordon@panix.com> - 2016-03-03 23:08 +0000
    Re: list reversal error Joel Goldstick <joel.goldstick@gmail.com> - 2016-03-03 18:13 -0500
    Re: list reversal error MRAB <python@mrabarnett.plus.com> - 2016-03-03 23:20 +0000
  Re: list reversal error Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-03 23:20 +0000
  Re: list reversal error Gary Herron <gherron@digipen.edu> - 2016-03-03 15:15 -0800
  Re: list reversal error Steven D'Aprano <steve@pearwood.info> - 2016-03-04 11:06 +1100

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