How do you change the contents of a form based on radio buttons?

Using Streamlit
5

How are you doing that? I have something like:

with st.form("form"):
    space_for_selecting_use_case = st.empty()

    if use_case == "complex":
        additional_input = st.text_input("Additional Input")

with space_for_selecting_use_case:
    use_case = st.radio(
        label = "Select your use case.",
        options = ("simple", "complex")
    )

I then get an error of “cannot access local variable ‘use_case’ where it is not associated with a value” when checking if use_case == "complex".

In the provided example, radio_option was only accessed in a different empty element, whose contents were defined after the section initializing radio_option itself. How would you access the value of radio_option in an if-statement in the form itself?