Send and Receive MIDI data from device using MIDO

st_midi_app.py

import time

import mido
import streamlit as st

EMPTY_DEVICE_PLACEHOLDER = "-"
LIGHT_PLACEHOLDER = "Light!"
NOTE_PLACEHOLDER = "Wait for note"


def main():
    # For an unknown reason sometimes not all MIDI ports are immediately detected?
    with st.sidebar:
        if "initialized" not in st.session_state:
            with st.sidebar:
                with st.spinner("Wait for Ports to load..."):
                    time.sleep(3)
                    st.session_state["initialized"] = True

        selected_action = st.selectbox(
            "What do you want to do?", (LIGHT_PLACEHOLDER, NOTE_PLACEHOLDER)
        )
        selected_midi_device = st.selectbox(
            "Select MIDI to send to"
            if selected_action == LIGHT_PLACEHOLDER
            else "Select MIDI to receive from",
            [EMPTY_DEVICE_PLACEHOLDER]
            + (
                mido.get_output_names()
                if selected_action == LIGHT_PLACEHOLDER
                else mido.get_input_names()
            ),
        )

    if selected_midi_device is not EMPTY_DEVICE_PLACEHOLDER:
        if selected_action == LIGHT_PLACEHOLDER:
            with mido.open_output(selected_midi_device) as outport:
                outport.send(mido.Message("note_on", channel=0, note=55))
                time.sleep(5)
                outport.send(mido.Message("note_off", channel=0, note=55))

        if selected_action == NOTE_PLACEHOLDER:
            with mido.open_input(selected_midi_device) as inport:
                st.markdown("Waiting for note input")
                msg = inport.receive()
                st.write(f"Received MIDI message: {msg}")


if __name__ == "__main__":
    main()