[Discuss-gnuradio] 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 Dulmage
#
##################################################

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:]))


------------------------------------------------------
Jared Dulmage
Engineering Specialist
Digital Comm. and Implementation Dept.
Aerospace Corporation
310-336-3140

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