list subsetting

culpritNr1 ig2ar-saf1 at yahoo.co.uk
Wed Jan 21 23:22:45 CET 2009


Thank you Fogelbird and Jeff.

I actually tried to find out if such function existed. I did

>>> help("count")
no Python documentation found for 'count'

Anyway. More than counting, I am interested in list subsetting in a simple
way. Forget about counting. Say I have a list of lists and I want to pull
only the rows where the second "column" equals 3.14.

It is a very simple concept. I wonder if python can keep it simple despite
being a general purpose programming language, not a numerical programming
language.

Thanks,

culpritNr1





Jeff McNeil-2 wrote:
> 
> On Jan 21, 4:53 pm, culpritNr1 <ig2ar-s... at yahoo.co.uk> wrote:
>> Hello All,
>>
>> Say I have a list like this:
>>
>> a = [0 , 1, 3.14, 20, 8, 8, 3.14]
>>
>> Is there a simple python way to count the number of 3.14's in the list in
>> one statement?
>>
>> In R I do like this
>>
>> a = c(0 , 1, 3.14, 20, 8, 8, 3.14)
>>
>> length( a[ a[]==3.14 ] )
>>
>> How do I do that in standard python?
>>
>> (Note that this is just an example, I do not mean to use == in floating
>> point operations.)
>>
>> Thank you
>>
>> culpritNr1
>>
>> --
>> View this message in
>> context:http://www.nabble.com/list-subsetting-tp21593123p21593123.html
>> Sent from the Python - python-list mailing list archive at Nabble.com.
> 
> Just the number of occurrences? Count method?
> 
> Python 2.6 (r26:66714, Oct 29 2008, 08:30:04)
> [GCC 4.1.2 20070925 (Red Hat 4.1.2-33)] on linux2
> Type "help", "copyright", "credits" or "license" for more information.
>>>> [1,2,3,3.14,3.14,5,66].count(3.14)
> 2
>>>>
> 
> Jeff
> --
> http://mail.python.org/mailman/listinfo/python-list
> 
> 

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