[Numpy-discussion] Enum type

Wes McKinney wesmckinn@gmail....
Tue Jan 3 12:46:11 CST 2012


On Tue, Jan 3, 2012 at 1:06 PM, Jim Vickroy <jim.vickroy@noaa.gov> wrote:
> On 1/3/2012 10:46 AM, Ognen Duzlevski wrote:
>> Hello,
>>
>> I am playing with adding an enum dtype to numpy (to get my feet wet in
>> numpy really). I have looked at the
>> https://github.com/martinling/numpy_quaternion and I feel comfortable
>> with my understanding of adding a simple type to numpy in technical
>> terms.
>>
>> I am mostly a C programmer and have programmed in Python but not at
>> the level where my code wcould be considered "pretty" or maybe even
>> "pythonic". I know enums from C and have browsed around a few python
>> enum implementations online. Most of them use hash tables or lists to
>> associate names to numbers - these approaches just feel "heavy" to me.
>>
>> What would be a proper "numpy approach" to this? I am looking mostly
>> for direction and advice as I would like to do the work myself :-)
>>
>> Any input appreciated :-)
>> Ognen
>
> Does "enumerate"
> (http://docs.python.org/library/functions.html#enumerate) work for you?
>
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That's not exactly what he means. The R lingo for this concept is
"factor" or a bit more common "categorical variable":

http://stat.ethz.ch/R-manual/R-patched/library/base/html/factor.html

FWIW R's factor type is implemented using hash tables. I do the same in pandas.

- Wes


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