numpy-discussion

[Numpy-discussion] dtype() examples that used to work

[Joris De R. <jo...@st...>]

Hi,

The following did once work in NumPy:

>>> dtype([int16])
>>> dtype([[int16]])
>>> dtype([uint,int32])
>>> dtype(['f8','S10'])

but now they all generate a "TypeError: data type not understood". Why?
I could not find the answer in help(dtype), the RecordArrays tutorial on 
scipy.org, the NumPy release notes, nor in the NumPy book.

J.


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Re: [Numpy-discussion] dtype() examples that used to work

[Francesc A. <fa...@ca...>]

A Divendres 27 Octubre 2006 18:13, Joris De Ridder va escriure:
> Hi,
>
> The following did once work in NumPy:
> >>> dtype([int16])
> >>> dtype([[int16]])
> >>> dtype([uint,int32])
> >>> dtype(['f8','S10'])
>
> but now they all generate a "TypeError: data type not understood". Why?

Should be intended as well. If you try to set a dtype from a list, it has t=
o=20
follow the format of a description as specified in:

http://numpy.scipy.org/array_interface.shtml

for example:

In [67]: dtype([('f1', int16)])
Out[67]: dtype([('f1', '<i2')])

In [68]: dtype([('f1', int16, (2,2))])
Out[68]: dtype([('f1', '<i2', (2, 2))])

In [69]: dtype([('f1', int16, (2,2)), ('f3', int32)])
Out[69]: dtype([('f1', '<i2', (2, 2)), ('f3', '<i4')])

Cheers,

=2D-=20
>0,0<   Francesc Altet =A0 =A0 http://www.carabos.com/
V   V   C=E1rabos Coop. V. =A0=A0Enjoy Data
 "-"

Re: [Numpy-discussion] dtype() examples that used to work

[Travis O. <oli...@ie...>]

Joris De Ridder wrote:
> Hi,
>
> The following did once work in NumPy:
>
>   
>>>> dtype([int16])
>>>> dtype([[int16]])
>>>> dtype([uint,int32])
>>>> dtype(['f8','S10'])
>>>>         
>
> but now they all generate a "TypeError: data type not understood". Why?
> I could not find the answer in help(dtype), the RecordArrays tutorial on 
> scipy.org, the NumPy release notes, nor in the NumPy book.
>   

It's in the release notes.   Look in the section from 1.0b2 to 1.0b3.  
It's highlighted with a Note:

*NOTE: * When creating data-type objects from lists, the list must be in 
array descriptor format. The "list of data-type objects" approach is no 
longer supported due to its ambiguity with the very common array 
descriptor approach. You can still get this behavior using a 
comma-separated string or changing your list to an array_descriptor: 
[('', x) for x in oldlist]


-Travis

Re: [Numpy-discussion] dtype() examples that used to work

[Joris De R. <jo...@st...>]

On Friday 27 October 2006 19:06, Francesc Altet wrote:
   [FA]: for example:
   [FA]: 
   [FA]: In [67]: dtype([('f1', int16)])
   [FA]: Out[67]: dtype([('f1', '<i2')])
   [FA]: 
   [FA]: In [68]: dtype([('f1', int16, (2,2))])
   [FA]: Out[68]: dtype([('f1', '<i2', (2, 2))])
   [FA]: 
   [FA]: In [69]: dtype([('f1', int16, (2,2)), ('f3', int32)])
   [FA]: Out[69]: dtype([('f1', '<i2', (2, 2)), ('f3', '<i4')])

Thanks, Francesc, for the examples!

IMO, record arrays seem powerful, but also intimidating at a first glance.
I think many didactical examples will help getting them into common use.
I made some effort to get updated examples in the Numpy Example List:

www.scipy.org/Numpy_Example_List#dtype
www.scipy.org/Numpy_Example_List#array

Could people who already have some experience with it, have a look at
them and give me their opinion?

Cheers,
Joris


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Re: [Numpy-discussion] dtype() examples that used to work

[Francesc A. <fa...@ca...>]

El dl 30 de 10 del 2006 a les 14:58 +0100, en/na Joris De Ridder va
escriure:
> IMO, record arrays seem powerful, but also intimidating at a first glance.

Agreed, specially if you start to nest datatypes.

> I think many didactical examples will help getting them into common use.
> I made some effort to get updated examples in the Numpy Example List:
> 
> www.scipy.org/Numpy_Example_List#dtype
> www.scipy.org/Numpy_Example_List#array
> 
> Could people who already have some experience with it, have a look at
> them and give me their opinion?

Looks good. I've taken the freedom to add some examples of nested types
and recarrays.

-- 
Francesc Altet    |  Be careful about using the following code --
Carabos Coop. V.  |  I've only proven that it works, 
www.carabos.com   |  I haven't tested it. -- Donald Knuth