Changing the value of a Python Variable into a block

[dubstep]

Hello!

I’m developing a TV enconder, and I need to extract information from my
input data, and this will be used to determine the parameters of other
blocks on the flow graph.
How can I change the value of a variable of the python (or grc)
environment
from the block general_work() method?

Thanks!

[SSAndrSS_SelvaSS_SS]

On 01/24/2012 10:42 AM, Andr S. wrote:

Hello!

I’m developing a TV enconder, and I need to extract information from my
input data, and this will be used to determine the parameters of other
blocks on the flow graph.
How can I change the value of a variable of the python (or grc) environment
from the block general_work() method?

Well, you generally cant call a python function from c++… but heres a
few ways that may accomplish what you need:

1. Using swig directors is a possibility. Rather than figure out the
   intricacies of directors, gnuradio already makes use of them in the
   gr.feval_* class, which you can use to call into a python object. Your
   general_work() calls the feval object in c++; and then feval object
   (from python) directly calls into other variables in the python-domain
   of your flow graph.

2. Another possibility is passing messages into a message queue object.
   A python thread can pop the messages and act upon them.

3. A related possibility, depending upon how your block operates would
   be to have a python thread periodically poll the getter methods of your
   custom block and act upon those values. There is already a block in grc
   that will poll another block’s getter function and update a variable.

4. You could write the general work in python, which means all of the
   parameter calculation and setting occurs entirely in python (this
   functionality is not yet officially accepted).
   http://gnuradio.org/redmine/projects/gnuradio/wiki/WriteBlocksInPython

5. And if thats not possible for performance reasons, you might consider
   a hybrid approach where you write general work in python, but you call
   into a function implemented in c++; where this function processes the
   input data and returns the “determined parameters”, which you can act on
   in python.

-Josh