A categorical column (“region”) has 5% missing values and the rest are roughly evenly distributed across four categories. Which strategy is most defensible?

The standard recommended Plotly continuous colormap (perceptually uniform, colorblind-friendly):

Trailing/leading whitespace in a string column is most cleanly removed with:

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: