Message passing: strobe or _post?

I am testing the capability of posting messages to Python blocks via
Python. I have included below a simple example in which the Python
block just prints out the message received. In one case, I send
messages to this block via the builtin gnuradio.blocks.message_strobe
block. In the other case I try to call _post on the block directly from
Python. The former case works, but not the latter. I’ve tried to delve
into the code, but so far have not found an answer. Any advice would be
appreciated.

Jared.

Ubuntu 14.04
Python 2.7.6
GR 3.7.8

#!/usr/bin/env python
##################################################

Message passing example

Jared D.

##################################################

from gnuradio import gr, blocks
import pmt
import json
import time

class message_print(gr.sync_block):
def init(self):
gr.sync_block.init(self, “message_print”, None, None)

    self.msg_port = mport = "in_port"
    self.message_port_register_in(pmt.intern(mport))
    self.set_msg_handler(pmt.intern(mport), self.print_msg)

def print_msg(self, msg):
    print "RECEIVED: ",
    print json.dumps(pmt.to_python(msg))

def main(*args):
if “strobe” in args:
main_strobe()
else:
main_no_strobe()

def main_no_strobe():
tb = gr.top_block()
msg_printer = message_print()
tb.connect(msg_printer)
tb.start()
for n in range(10):
time.sleep(0.1)
msg_printer.to_basic_block()._post(pmt.intern(msg_printer.msg_port),
pmt.to_pmt({‘NUM’: n}))
tb.stop()
tb.wait()

def main_strobe():
tb = gr.top_block()
msg_printer = message_print()
msg_strobe = blocks.message_strobe(pmt.to_pmt({‘NUM’: -1}), 100)
tb.msg_connect(msg_strobe, “strobe”, msg_printer,
msg_printer.msg_port)
tb.start()
time.sleep(1)
tb.stop()
tb.wait()

if name == ‘main’:
import sys
sys.exit(main(*sys.argv[1:]))