Modify variable values in bdb without ctypes

Question

I have a class extending bdb.Bbd that I use for analyzing Python 3 code. Now, I need to also modify some of the variable values as it steps through the program.

Outside of functions, I can do this by just modifying the frame.f_locals dictionary:

frame.f_locals['x'] = 2

I can't figure out how to do this inside functions without using the ctypes trick mentioned in this question. I'm running Python 3 inside Pyodide which unfortunately does not support ctypes yet.

score 2 · Accepted Answer · answered Mar 12 '21 at 07:50

It should be possible to do this as follows. Define a Javascript function:

function frameLocalsToFast(frame){
   pyodide._module._PyFrame_LocalsToFast(frame.$$.ptr, 0);
   // Hopefully avoid memory leak
   frame.destroy();
}

Then import frameLocalsToFast into Python and call it when you want to update the frame.

Modify variable values in bdb without ctypes

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