[Numpy-discussion] question about creating numpy arrays

[Darren Dale]

On Wed, May 19, 2010 at 4:19 PM,  <josef.pktd at gmail.com> wrote:
> On Wed, May 19, 2010 at 4:08 PM, Darren Dale <dsdale24 at gmail.com> wrote:
>> I have a question about creation of numpy arrays from a list of
>> objects, which bears on the Quantities project and also on masked
>> arrays:
>>
>>>>> import quantities as pq
>>>>> import numpy as np
>>>>> a, b = 2*pq.m,1*pq.s
>>>>> np.array([a, b])
>> array([ 12.,   1.])
>>
>> Why doesn't that create an object array? Similarly:
>>
>>>>> m = np.ma.array([1], mask=[True])
>>>>> m
>> masked_array(data = [--],
>>             mask = [ True],
>>       fill_value = 999999)
>>
>>>>> np.array([m])
>> array([[1]])
>>
>> This has broader implications than just creating arrays, for example:
>>
>>>>> np.sum([m, m])
>> 2
>>>>> np.sum([a, b])
>> 13.0
>>
>> Any thoughts?
>
> These are "array_like" of floats, so why should it create anything
> else than an array of floats.

I gave two counterexamples of why.