text: Q:
  
  How to make a numpy recarray with datatypes (datetime,float)?
  
  Let's say I have some simple data
  y = [[datetime.datetime( 2012,1,1,1,1), 2.1], 
       [datetime.datetime( 2012,1,1,1,2), -3.1],
       [datetime.datetime( 2012,1,1,1,3), 0.1]]
  
  and I want a numpy record array corresponding to it.  It would seem I ought to be able to do this:
  np.rec.array( y, dtype=[('timestamp', object),('x','f')] )
  
  or this
  np.rec.array( y, dtype=[('timestamp', '|O8'),('x','f')] )
  
  or maybe this
  np.rec.array( y, dtype=[('timestamp', 'V'),('x','f')] )
  
  But each of them returns an error, either
  ValueError: Setting void-array with object members using buffer.
  
  or
  TypeError: expected a readable buffer object
  
  So how exactly can I set this up, assuming it is even possible?
  
  A:
  
  You can use tuples instead of lists for the records:
  >> y = [(datetime.datetime( 2012,1,1,1,1), 2.1), 
  ...     (datetime.datetime( 2012,1,1,1,2), -3.1),
  ...     (datetime.datetime( 2012,1,1,1,3), 0.1)]
  >> np.rec.array(y, dtype=[('timestamp', object), ('x','f')])
  rec.array([(datetime.datetime(2012, 1, 1, 1, 1), 2.0999999046325684),
             (datetime.datetime(2012, 1, 1, 1, 2), -3.0999999046325684),
             (datetime.datetime(2012, 1, 1, 1, 3), 0.10000000149011612)],
  dtype=[('timestamp', '|O8'), ('x', '<f4')])
  
  