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Re: Need help understanding list structure

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From Erik <python@lucidity.plus.com>
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Subject Re: Need help understanding list structure
Date Mon, 2 May 2016 22:48:33 +0100
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On 02/05/16 22:30, moa47401@gmail.com wrote:
> Can someone help me understand why or under what circumstances a list
> shows pointers instead of the text data?

When Python's "print" statement/function is invoked, it will print the 
textual representation of the object according to its class's __str__ or
__repr__ method. That is, the print function prints out whatever text
the class says it should.

For classes which don't implement a __str__ or __repr__ method, then
the text "<CLASS object at ADDRESS>" is used - where CLASS is the class
name and ADDRESS is the "memory pointer".

 > If I iterate over the list, I do get the actual text of each element
 > and am able to use it.
 >
 > Also, if I iterate over the list and place each element in a new list
 > using append, then each element in the new list is the text I expect
 > not memory pointers.

Look at the __iter__ method of the class of the object you are iterating 
over. I suspect that it returns string objects, not the objects that are 
in the list itself.

String objects have a __str__ or __repr__ method that represents them as 
the text, so that is what 'print' will output.

Hope that helps, E.

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Thread

Need help understanding list structure moa47401@gmail.com - 2016-05-02 14:30 -0700
  Re: Need help understanding list structure Erik <python@lucidity.plus.com> - 2016-05-02 22:48 +0100
    Re: Need help understanding list structure moa47401@gmail.com - 2016-05-02 15:33 -0700
      Re: Need help understanding list structure Michael Torrie <torriem@gmail.com> - 2016-05-02 17:25 -0600
      Re: Need help understanding list structure Ben Finney <ben+python@benfinney.id.au> - 2016-05-03 09:43 +1000
        Re: Need help understanding list structure moa47401@gmail.com - 2016-05-03 06:21 -0700
          Re: Need help understanding list structure Chris Angelico <rosuav@gmail.com> - 2016-05-03 23:47 +1000
            Re: Need help understanding list structure moa47401@gmail.com - 2016-05-03 09:01 -0700
              RE: Need help understanding list structure Dan Strohl <D.Strohl@F5.com> - 2016-05-03 16:52 +0000
                Re: Need help understanding list structure moa47401@gmail.com - 2016-05-03 10:31 -0700
                RE: Need help understanding list structure Dan Strohl <D.Strohl@F5.com> - 2016-05-03 17:54 +0000
                Use __repr__ to show the programmer's representation (was: Need help understanding list structure) Ben Finney <ben+python@benfinney.id.au> - 2016-05-04 04:14 +1000
                RE: Use __repr__ to show the programmer's representation (was: Need help understanding list structure) Dan Strohl <D.Strohl@F5.com> - 2016-05-03 18:35 +0000
                Re: Use __repr__ to show the programmer's representation (was: Need help understanding list structure) moa47401@gmail.com - 2016-05-03 12:24 -0700
                Re: Use __repr__ to show the programmer's representation (was: Need help understanding list structure) Random832 <random832@fastmail.com> - 2016-05-03 15:37 -0400
                Re: Need help understanding list structure MRAB <python@mrabarnett.plus.com> - 2016-05-03 20:57 +0100
                Re: Use __repr__ to show the programmer's representation (was: Need help understanding list structure) Chris Angelico <rosuav@gmail.com> - 2016-05-04 09:40 +1000

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