Question

I have a class that defines the __complex__ special method. My class is not a standard numeric type (int, float, etc.), but it behaves like one as I have special methods defined for __add__, __sub__, etc.

I would like __complex__ to return my complex valued numeric object, not a standard complex numeric value python expects. As such, Python throws the following error when I try to return my object, rather than a standard complex numeric.

TypeError: unsupported operand type(s) for *: ‘complex’ and
‘MyNumericClass’

What’s the best way to do this?

---

Edit:

# Python builtins
import copy
# Numeric python
import numpy as np

class MyNumericClass (object):
    """ My numeric class, with one single attribute """
    def __init__(self, value):
        self._value = value

    def __complex__(self):
        """ Return complex value """
        # This looks silly, but my actual class has many attributes other
        # than this one value.
        self._value = complex(self._value)
        return self

def zeros(shape):
    """
    Create an array of zeros of my numeric class

    Keyword arguments:
      shape -- Shape of desired array
    """
    try:
        iter(shape)
    except TypeError, te:
        shape = [shape]
    zero = MyNumericClass(0.)
    return fill(shape, zero)

def fill(shape, value):
    """
    Fill an array of specified type with a constant value

    Keyword arguments:
      shape -- Shape of desired array
      value -- Object to initialize the array with
    """
    try:
        iter(shape)
    except TypeError, te:
        shape = [shape]
    result = value
    for i in reversed(shape):
        result = [copy.deepcopy(result) for j in range(i)]
    return np.array(result)

if __name__ == '__main__':
    a_cplx = np.zeros(3).astype(complex)
    print a_cplx
    b_cplx = zeros(3).astype(complex)
    print b_cplx

Answer 1

A couple of options:

1. Define __rmul__ (or define __mul__ and flip the multiplication operands).
2. Cast your MyNumericClass instance to complex before multiplying.