Applying method to objects in a numpy array with vectorize results in empty array

Question

I want to apply a method to each object in a numpy array. I thought of using numpy.vectorize to speed things up, but I get an empty array instead. I can't figure out what I am doing wrong. Please help!

Here's the code:

import numpy

class Foo(object):
  def __init__(self):
    self.x = None
  def SetX(self, x):
    self.x = x
# Initialize and array of Foo objects
y = numpy.empty( 3, dtype=object )
vFoo = numpy.vectorize(lambda x: Foo() )
yfoo = vFoo(y)
# Apply method SetX to each object
xsetter = numpy.vectorize( lambda foo: foo.SetX(3.45) )
print xsetter(yfoo) #[None None None]

Thanks in advance!

Answer 1

The problem is that the lambda function return values is None (the result of Foo.SetX ), you can do this:

def f(foo):
    foo.SetX(3.45)
    return foo
xsetter = numpy.vectorize( f )

Answer 2

It's because your SetX method does not return a value. One way to fix this would be by rewriting SetX as

def SetX(self, x):
  self.x = x
  return self