Update app.py

app.py

@@ -2,6 +2,10 @@ import streamlit as st
 import matplotlib.pyplot as plt
 import networkx as nx
 
+# Initialize session state variable if it does not exist
+if 'graph_displayed' not in st.session_state:
+    st.session_state.graph_displayed = False
+
 # Sidebar for selecting an option
 sidebar_option = st.sidebar.radio("Select an option", 
                                  ["Select an option", "Basic: Properties", 
@@ -161,7 +165,7 @@ elif sidebar_option == "Basic: Simple graph":
         display_simple_graph(G, pos)
 
     # Default example: directed graph with custom positions (added the missing part)
-    if option == "Default Example" and st.session_state.graph_displayed == False:
+    if option == "Default Example" and not st.session_state.graph_displayed:
         G = nx.DiGraph([(0, 3), (1, 3), (2, 4), (3, 5), (3, 6), (4, 6), (5, 6)])
 
         # Group nodes by column