Hi @shuchao.lv,
Unfortunately, streamlit apps really do need to be kicked off from streamlit run in order for you to see their effects.
That DeltaGenerator object you’re seeing is the intermediate step before the streamlit engine “notices” a new element and has it picked up by the frontend. None of that machinery will be in place if you’re not running the streamlit engine directly.
You can use tools like PyCharm and VScode (here’s a discussion thread about it) to set breakpoints in your code to dump variables and break out into a debugger while the script is running.
What will be going on while using the debugger is that you will still be running streamlit run yourscript.py and the output will still be shown in the browser.