I'm creating a Python block that calculates a custom FFT. I need to ensure
that I get at least 1024 data points for every input to the block.

>From my reading, it looks like I should just be able to do this with the
forecast() function in the Python block. So I've done this:

class blk(gr.sync_block):  # other base classes are basic_block,
> decim_block, interp_block
>
>     def __init__(self, bandWidthMHz=100.0):  # only default arguments here
>         """arguments to this function show up as parameters in GRC"""
>         gr.sync_block.__init__(
>             self,
>             name='test',   # will show up in GRC
>             in_sig=[np.complex64],
>             out_sig=[np.float32]
>        )
>         # if an attribute with the same name as a parameter is found,
>         # a callback is registered (properties work, too).
>         self.bandWidthMHz = bandWidthMHz
>         self.MM = 0
>
>     def forecast(self, noutput_items, ninput_items_required=1024):
>         ninput_items_required[0] = 1024
>
>     def work(self, input_items, output_items):
>         if (np.shape(input_items[0])[0] < 1024):
>             print(np.shape(input_items[0]))
>         output_items[0] = [3.5, -1, 0, 1]
>         return len(output_items[0])
>

According to the docs, if I set ninput_items_required[0] = 1024, then
forecast should prevent the work from being done until I have at least 1024
input values.

Nevertheless, the print statement I have in the work function is showing
that the program gets to the work even when the input_items[0] is much less
(e.g. 24, 102, 960) than 1024.

Can anyone point me in the right direction? Can I just have the work
function skip execution if len(input_items[0]) < 1024? Or, will that drop
data?

Thanks for your help.
-Tony

p.s. I'm just doing this in a Python block from the GRC. So this is not a
custom OOT module. Does that matter?
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