Blynk Python was in Alpha not too long ago… not sure it’s status now. But always best to refer to the GitHub pages examples for clues how to run the commands. Digging into the library file can also be a clue for commands not shown in the examples (like set parameter)
Meanwhile, I just (yesterday?) posted an example of how to changes images in the Image Gallery Widget, with both C++ and Python, based on a button press. You would just substitute the virtual write with your choice of GPIO control