deno_python exposes Python modules to JavaScript in a way that makes it possible access the API of any Python module out of the box, as if it were a JS API. Executing a Python shell command is quite different.
Here, FFI is used to interface with the Python Interpreter C API. Argument for FFI against just executing shell commands is performance, efficiency, and that you can make calls from same process instead of spawning a subprocess. When doing [de]serialization over shell interface, a lot of things will be hit and miss. But for deno_python, type conversions are widely supported. You can even pass around objects by reference with zero copy, which would otherwise require copy over a shell interface.
Here, FFI is used to interface with the Python Interpreter C API. Argument for FFI against just executing shell commands is performance, efficiency, and that you can make calls from same process instead of spawning a subprocess. When doing [de]serialization over shell interface, a lot of things will be hit and miss. But for deno_python, type conversions are widely supported. You can even pass around objects by reference with zero copy, which would otherwise require copy over a shell interface.