Hi,
I believe some other guys met this problem before, but I did not find the final solution expressed clearly.
After I installed the gnuradio, grextras, then in my python code which trys to import the extras_swig like
import gnuradio.extras as gr_extras
File "/usr/local/lib/python2.7/dist-packages/gnuradio/extras/__init__.py", line 20, in <module>
from extras_swig import *
File "/usr/local/lib/python2.7/dist-packages/gnuradio/extras/extras_swig.py", line 26, in <module>
_extras_swig = swig_import_helper()
File "/usr/local/lib/python2.7/dist-packages/gnuradio/extras/extras_swig.py", line 22, in swig_import_helper
_mod = imp.load_module('_extras_swig', fp, pathname, description)
ImportError: /usr/local/lib/libgnuradio-extras.so: undefined symbol: _ZN15gr_msg_accepter4postEN5boost13intrusive_ptrIN3pmt8pmt_baseEEES4_