[Numpy-discussion] use of concatenate with subclass of ndarray

Bryce Hendrix bhendrix@enthought....
Tue Mar 27 19:08:04 CDT 2007

We have a class which is a subclass of ndarray which defines 
__array_finalize__ to add an attribute. The class looks something like 

class UnitArray(ndarray):
 # ...
 def __new__(cls, data, dtype=None, copy=True, units=None):
   # ...
   arr = array(data, dtype=dtype, copy=copy)
   res = ndarray.__new__(cls, arr.shape, arr.dtype,buffer=arr)
   res.units = units
   return res

 def __array_finalize__(self, obj):
   if (isinstance(obj, UnitArray)):
     if hasattr(obj, 'units'):
       self.units = obj.units

This works for all the ufuncs I've tried, but the result of concatenate 
is missing the units attribute. Is this a bug with concatenate, or 
expected behavior?

The real class can be found here:


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