It looks that my 3.6.4git versio doesn't support message passing logic within python, so I switched to another pc where I run 3.7.0. I assume that because there is no function for registering message ports, but when I changed to 3.7.0, there was no that error any more.
def __init__(self):
gr.sync_block.__init__(self,
name="msg_sender",
in_sig=[numpy.int8],
out_sig=[None])
self.message_port_register_out(pmt.pmt_intern('out_port'))
but when i run flowgraph, the following error comes out:
RuntimeError: msg_sender(2): insufficient connected output ports (1 needed, 0 connected)
From where came that output that I havent declared?
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Nemanja Savić