[Numpy-discussion] Re: array of arbitrary objects

[Tim Hochberg]

Albert Strasheim wrote:

>Hello all
>
>  
>
>>-----Original Message-----
>>From: numpy-discussion-admin at lists.sourceforge.net [mailto:numpy-
>>discussion-admin at lists.sourceforge.net] On Behalf Of Robert Kern
>>Sent: 11 May 2006 05:28
>>To: numpy-discussion at lists.sourceforge.net
>>Subject: [Numpy-discussion] Re: array of arbitrary objects
>>
>>Ryan Krauss wrote:
>>    
>>
>>>Is it possible with numpy to create arrays of arbitrary objects?
>>>Specifically, I have defined a symbolic string class with operator
>>>overloading for most simple math operations: 'a'*'b' ==> 'a*b'
>>>
>>>Can I create two matrices of these symbolic string objects and
>>>multiply those matrices together?
>>>
>>>(simply doing array([[a,b],[c,d]]) did not work.  the symbolic strings
>>>got cast to regular strings)
>>>      
>>>
>>Use dtype=object .
>>    
>>
>
>How does one go about putting tuples into an object array?
>
>Consider the following example, courtesy of Louis Cordier:
>
>In [1]: import numpy as N
>In [2]: a = [(1,2), (2,3), (3,4)]
>In [3]: len(a)
>Out[3]: 3
>In [5]: N.array(a, 'O')
>Out[5]:
>array([[1, 2],
>       [2, 3],
>       [3, 4]], dtype=object)
>
>instead of something like this:
>
>array([[(1, 2), (2, 3), (3, 4)]], dtype=object)
>  
>
Creating object arrays is always going to be a bit of a pain, however, 
the following approach will work here:

 >>> import numpy as N
 >>> a = [(1,2), (2,3), (3,4)]
 >>> b = N.zeros([len(a)], object)
 >>> b[:] = a
 >>> b
array([(1, 2), (2, 3), (3, 4)], dtype=object)
 >>> type(b[0])
<type 'tuple'>


Regards,

-tim