Re: [Tutor] Accesing "column" of a 2D list

[Kent Johnson]

Ian Witham wrote:
> This looks like a job for List Comprehensions!
> 
>  >>> list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
>  >>> new_list = [item[1] for item in list]
>  >>> new_list
> [2, 5, 8]
>  >>>

Alternately, if you want *all* columns, you can use zip() to transpose 
the lists:

In [1]: lst = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
In [2]: zip(*lst)
Out[2]: [(1, 4, 7), (2, 5, 8), (3, 6, 9)]

PS. Don't use 'list' as the name of a list, it shadows the builtin 
'list' which is the  of list. Similarly, avoid str, dict, set and 
file as names.

Kent

> looks good?
> 
> Ian
> 
> On 8/21/07, *Orest Kozyar* <[EMAIL PROTECTED] 
> > wrote:
> 
> I've got a "2D" list (essentially a list of lists where all sublists
> are of
> the same length).  The sublists are polymorphic.  One "2D" list I
> commonly
> work with is:
> 
> [ [datetime object, float, int, float],
>   [datetime object, float, int, float],
>   [datetime object, float, int, float] ]
> 
> I'd like to be able to quickly accumulate the datetime column into a
> list.
> Is there a simple/straightforward syntax (such as list[:][0]) to do
> this, or
> do we need to use a for loop?  I expect what I have in mind is
> similar to
> the Python array type, except it would be polymorphic.
> 
> Thanks,
> Orest
> 
> ___
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> http://mail.python.org/mailman/listinfo/tutor
> 
> 
> 
> 
> 
> ___
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Re: [Tutor] Accesing "column" of a 2D list

[Ian Witham]

This looks like a job for List Comprehensions!

>>> list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
>>> new_list = [item[1] for item in list]
>>> new_list
[2, 5, 8]
>>>

looks good?

Ian

On 8/21/07, Orest Kozyar <[EMAIL PROTECTED]> wrote:
>
> I've got a "2D" list (essentially a list of lists where all sublists are
> of
> the same length).  The sublists are polymorphic.  One "2D" list I commonly
> work with is:
>
> [ [datetime object, float, int, float],
>   [datetime object, float, int, float],
>   [datetime object, float, int, float] ]
>
> I'd like to be able to quickly accumulate the datetime column into a list.
> Is there a simple/straightforward syntax (such as list[:][0]) to do this,
> or
> do we need to use a for loop?  I expect what I have in mind is similar to
> the Python array type, except it would be polymorphic.
>
> Thanks,
> Orest
>
> ___
> Tutor maillist  -  Tutor@python.org
> http://mail.python.org/mailman/listinfo/tutor
>
___
Tutor maillist  -  Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor