[Tutor] Delete unwanted rows

[Mark Lawrence]

On 09/04/2014 10:23, Alexis Prime wrote:
> Hello,
>
> My question is whether I should write a loop or a function to delete rows.
>
> I'm using pandas. But you may be able to help me as my question is about
> the reasoning behind programming.
>
> I have a pandas dataframe that looks like this, covering all countries
> in the world, for over 200 rows and many columns:
>
> Canada                20
> China                  112
> Germany             10
> Japan                  12
> Martinique             140
> Mexico                180
> Saint Kitts            90
> Saint Martins        133
> Saint Helena         166
> USA                    18
>
> # So I write a list of small countries that I wish to exclude from my
> analysis. What I want to do is to delete the rows from my dataframe.
>
>      toexclude = ['Martinique', 'Saint Kitts', 'Saint Martins', 'Saint
> Helena']
>
> After this, should I write a loop to loop through the dataframe, find
> the countries that I want to delete, and then delete the rows?
>
> Or should I write a function, which deletes those rows, and then returns
> me a new and trimmed dataframe?
>
> Thank you for helping me figure this out.
>
> Alexis
>

If you are going to do this repeatedly you'd be better off writing a 
function.  I don't know enough about pandas to say whether the rows 
should be deleted within a loop in the function or a new data frame is 
returned.  But before you write any code, have to checked to see if 
there is a function or method in pandas that does this for you?

-- 
My fellow Pythonistas, ask not what our language can do for you, ask 
what you can do for our language.

Mark Lawrence

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