Head gr_head from gnuradio import gr gr.head($type.size*$vlen, $num_items) 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 Num Items num_items 1024 int Vec Length vlen 1 int $vlen > 0 in $type $vlen out $type $vlen