On Fri, Jan 27, 2012 at 21:17, Emmanuel Mayssat <emayssat@gmail.com> wrote:

In [20]: dt_knobs = [('pvName',(str,40)),('start','float'),('stop','float'),('mode',(str,10))]

In [21]: r_knobs = np.recarray([],dtype=dt_knobs)

In [22]: r_knobs Out[22]: rec.array(('\xa0\x8c\xc9\x02\x00\x00\x00\x00(\xc8v\x02\x00\x00\x00\x00\x00\xd3\x86\x02\x00\x00\x00\x00\x10\xdeJ\x02\x00\x00\x00\x00\x906\xb9\x02', 1.63e-322, 1.351330465085e-312, '\x90\xc6\xa3\x02\x00\x00\x00\x00P'),      dtype=[('pvName', '|S40'), ('start', '<f8'), ('stop', '<f8'), ('mode', '|S10')])

why is the array not empty?

The shape [] creates a rank-0 array, which is essentially a scalar. [~] |1> x = np.array(10) [~] |2> x array(10) [~] |3> x.shape () If you want an empty array, you need at least one dimension of size 0: [~] |7> r_knobs = np.recarray([0], dtype=dt_knobs) [~] |8> r_knobs rec.array([], dtype=[('pvName', '|S40'), ('start', '<f8'), ('stop', '<f8'), ('mode', '|S10')]) -- Robert Kern "I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth."   -- Umberto Eco