[SciPy-user] Newbie broadcasting question

[John Reid]

This works fine:

In [49]: numpy.zeros((3,2))+numpy.array([1,2])
Out[49]:
array([[ 1.,  2.],
        [ 1.,  2.],
        [ 1.,  2.]])


but this doesn't:
In [50]: numpy.zeros((3,2))+numpy.array([1,2,3])
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)

C:\Dev\MyProjects\Bio\Python\site_dpm\<ipython console> in <module>()

ValueError: shape mismatch: objects cannot be broadcast to a single shape
 > <ipython console>(1)<module>()



what is the simplest way to get this addition to work? I would like the 
following

array([[ 0.,  0.],
        [ 0.,  0.],
        [ 0.,  0.]])


+

array([1,2,3])

=

array([[ 1.,  1.],
        [ 2.,  2.],
        [ 3.,  3.]])

In general my arrays are held in variables and are not constructed on 
the fly so while this works

numpy.zeros((3,2)).T+numpy.array([1,2,3])

which works fine with the '+' operator but not with '+='. This doesn't work:
In [54]: a=zeros((3,2))

In [55]: a.T += numpy.array([1,2,3])
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)

C:\Dev\MyProjects\Bio\Python\site_dpm\<ipython console> in <module>()

AttributeError: attribute 'T' of 'numpy.ndarray' objects is not writable
 > <ipython console>(1)<module>()


My guess is that I should do
a = (a.T + numpy.array([1,2,3])).T

but I wonder if there is a more efficient way. Am I missing something?

Thanks,
John.