Null Source gr_null_source from gnuradio import gr gr.null_source($type.size*$vlen) Output Type type enum Complex complex size:gr.sizeof_gr_complex Float float size:gr.sizeof_float Int int size:gr.sizeof_int Short short size:gr.sizeof_short Byte byte size:gr.sizeof_char Vec Length vlen 1 int $vlen > 0 out $type $vlen