On Aug 18, 10:03 pm, Nobody <nob...@nowhere.com> wrote: > On Wed, 18 Aug 2010 05:56:27 -0700, Duim wrote: > > Although I'm sure somewhere this issue is discussed in this (great) > > group, I didn't know the proper search words for it (although I > > tried). > > > I'm using python (2.6) scientifically mostly, and created a simple > > class to store time series (my 'Signal' class). > > I need this class to have a possibility to get multiplied by an array, > > but pre and post multiplication have different mathematical outcomes > > ( basically A* B != B*A ) . > > > Post multiplication by an array works fine defining __mul__ in the > > Signal class, but pre multiplication does not. It keeps trying to > > multiply all elements separately instead to send this array to my > > __rmul__ function. > > > How can I fix this without the need for a separate > > 'multiplysignal(A,B)' function? > > Make Signal a subclass of numpy.ndarray. If one operand is a subclass of > the other, its __rmul__ will be preferred to the parent's __mul__. > > In the absence of a subclass-superclass relationship, the LHS's __mul__ is > preferred to the RHS's __rmul__, so the RHS's __rmul__ is only called if > the LHS lacks a __mul__ method or if the method refuses its argument > (returns NotImplemented). > > Likewise for other "reflected" methods.
Great, many thanks. It seems to work well. For others looking into the same issue: http://www.scipy.org/Subclasses -- http://mail.python.org/mailman/listinfo/python-list
