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. -- http://mail.python.org/mailman/listinfo/python-list
