[Numpy-discussion] draft enum NEP

Dag Sverre Seljebotn d.s.seljebotn@astro.uio...
Wed Mar 14 00:08:38 CDT 2012

On 03/13/2012 06:44 PM, Mark Wiebe wrote:
> On Fri, Mar 9, 2012 at 8:55 AM, Bryan Van de Ven <bryanv@continuum.io
> <mailto:bryanv@continuum.io>> wrote:
>     Hi all,
>     I have started working on a NEP for adding an enumerated type to NumPy.
>     It is on my GitHub:
>     https://github.com/bryevdv/numpy/blob/enum/doc/neps/enum.rst
>     It is still very rough, and incomplete in places. But I would like to
>     get feedback sooner rather than later in order to refine it. In
>     particular there are a few questions inline in the document that I would
>     like input on. Any comments, suggestions, questions, concerns, etc. are
>     very welcome.
> This looks like a great start to me.
> I think the open/closed enum distinction will need to be explored a
> little bit more, because it interacts with dtype
> immutability/hashability. Do you know if there are any examples of
> Python objects in the wild that dynamically convert from not being
> hashable (i.e. raising an exception if used as a dict key) to become
> hashable?

In Sage, the matrix objects are mutable when constructed, and you can 
set_immutable to make them immutable.

The way I look at that though is that it is part of the construction 
phase of the object, you'd typically construct, fill it in, then 
set_immutable (to finish construction), then use it.

set/frozenset is an example of the opposite, and a design I personally 
like better (i.e., "frozen_dtype" :-)).


> It might be worth adding a section which briefly compares and contrasts
> the proposed functionality with enums in various programming languages.
> Here are two links I found to try and get an idea:
> MS on C# enum usage:
> http://msdn.microsoft.com/en-us/library/cc138362.aspx
> Wikipedia on C++ enum class:
> http://en.wikipedia.org/wiki/C%2B%2B11#Strongly_typed_enumerations
> For example, the C# enum has a way to enable a "flags" mode, which will
> create successive powers of 2. This may not be a feature NumPy needs,
> but if people are finding it useful in C#, maybe it would be useful here
> too.
> Cheers,
> Mark
>     Thanks,
>     Bryan
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