Re: Can Embedded Python Blocks have callbacks?

Thanks!  That worked.  Here's a full working block:

"""
Embedded Python Blocks:

Each time this file is saved, GRC will instantiate the first class it finds
to get ports and parameters of your block. The arguments to __init__  will
be the parameters. All of them are required to have default values!
"""

import numpy as np
from gnuradio import gr

```
class blk(gr.sync_block):  # other base classes are basic_block, decim_block, interp_block
    """Embedded Python Block example - a simple multiply const"""

    def __init__(self, example_param=1.0):  # only default arguments here
        """arguments to this function show up as parameters in GRC"""
        gr.sync_block.__init__(
            self,
            name='Embedded Python Block',   # will show up in GRC
            in_sig=[np.complex64],
            out_sig=[np.complex64]
        )
        # if an attribute with the same name as a parameter is found,
        # a callback is registered (properties work, too).
        self.example_param = example_param

    def work(self, input_items, output_items):
        """example: multiply with constant"""
        output_items[0][:] = input_items[0] * self.example_param
        return len(output_items[0])
   
    @property
    def example_param(self):
        return self._example_param
 
    @example_param.setter
    def example_param(self, value):
       print('here')
       self._example_param = value

```

On Tue, Jun 25, 2024 at 8:33 AM Philipp Niedermayer <p.niedermayer@gsi.de> wrote:

As a workaround, use python's property construct to intercept changes on class attribute level:

class blk(...):

    def __init__(self, example_param=1.0):

        ...

        # [...] (properties work, too)

        self.example_param = example_param

   

    @property

    def example_param(self):

        return self._example_param

  


    @example_param.setter

    def example_param(self, value):

       print('here')


       self._example_param = value


---

From: Jameson Collins [mailto:jameson.collins@gmail.com]

Date: Thursday, June 20, 2024 at 14:10 UTC+2

Subject: Can Embedded Python Blocks have callbacks?

This was my concern, and it does appear to behave that way.

On Wed, Jun 19, 2024 at 4:34 PM Daniel Estévez <daniel@destevez.net> wrote:

On 19/06/2024 14:51, Jameson Collins wrote:
> I'm trying to use a callback to set a variable in an embedded python
> block.  Using the tutorial
> (https://wiki.gnuradio.org/index.php/Embedded_Python_Block
> <https://wiki.gnuradio.org/index.php/Embedded_Python_Block>) as an
> example I added the function below.  I've found that this callback never
> gets called when I update this value from a GUI.  Should it be?
>
> |def set_example_param(self, example_param): print("here")|

Hi Jameson,

I think Embedded Python blocks can only have (automatically generated)
callbacks for __init__() arguments that are assigned as

self.foo = foo

in the body of __init__() (the example template that you get when you
create a new Embedded Python block shows how this works).

If you need more complex callbacks, I think you need to create a regular
Python block in an OOT module.

Best,
Daniel.