[Numpy-discussion] Enum type

Ognen Duzlevski ognen@enthought....
Tue Jan 3 12:52:30 CST 2012


On Tue, Jan 3, 2012 at 12:46 PM, Wes McKinney <wesmckinn@gmail.com> wrote:
> 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?
> 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

Wes,

You are right, "categorical variable" is what I am after. Thanks for
the pointer, I will go the klib route you suggested and see what comes
out. I may be "old fashioned" a bit in the sense that adding
dependencies on external libraries is something I am reluctant to do -
this is why I said using hashes may have felt a bit "heavy". But that
may be my shortcoming :-)

Ognen


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