working dropdown

app.py

@@ -87,13 +87,47 @@ def tree_to_dot(graph: Dict[str, Any]) -> str:
     return "\n".join(lines)
 
 def main():
-    st.title("Math Genealogy Ancestor Tree (WebSocket API)")
-    mgp_id_str = st.text_input("Enter MGP ID (integer):")
+    st.title("Math Genealogy Ancestor Tree")
+
+    mathematicians = [
+        ("Tristan Hearn", 162833),
+        ("Alexander Grothendieck", 31245),
+        ("Emmy Noether", 6967),
+        ("David Hilbert", 7298),
+        ("Sophie Germain", 55175),
+        ("Carl Friedrich Gauss", 18231),
+    ]
+    names = [f"{name} ({mid})" for name, mid in mathematicians]
+    default_index = 0  # Tristan Hearn
+
+    # initialize session state for mgp_id_str if not set
+    if "mgp_id_str" not in st.session_state:
+        st.session_state["mgp_id_str"] = str(mathematicians[default_index][1])
+
+    mgp_id_str = st.text_input(
+        "Enter MGP ID (integer):",
+        value=st.session_state["mgp_id_str"],
+        key="mgp_id_str",
+        help="You can type a custom ID or use the selection below."
+    )
+
+    def on_select():
+        st.session_state["mgp_id_str"] = str(mathematicians[st.session_state["mathematician_idx"]][1])
+
+    selected_idx = st.selectbox(
+        "Or select a mathematician:",
+        range(len(names)),
+        format_func=lambda i: names[i],
+        index=default_index,
+        key="mathematician_idx",
+        on_change=on_select,
+    )
+
     progress_placeholder = st.empty()
     graph_placeholder = st.empty()
     run_btn = st.button("Show Ancestor Tree")
     if run_btn:
-        mgp_id = get_id_from_input(mgp_id_str)
+        mgp_id = get_id_from_input(st.session_state["mgp_id_str"])
         if mgp_id is None:
             st.error("Please enter a valid integer MGP ID.")
             return