When should st.radio be preferred over st.selectbox?

Which is a quantifier in regex?

To split a “full_name” column (“Jane Doe”) into “first” and “last” columns, the cleanest call is:

In regex, what does the ? quantifier mean?

You apply str.contains to a column that has some NaN values. Without the na argument, what happens?

To preserve a value across script reruns in Streamlit (e.g., remembering whether the user clicked a button):

To display a Plotly figure with full interactivity in Streamlit:

To split the main area into a 2:1 layout (chart on left, controls on right):

Which command starts a Streamlit app from app.py?

To collect multiple inputs and submit them together (so the page doesn’t rerun on every keystroke), use: