Update app.py

app.py

@@ -1,5 +1,6 @@
 import gradio as gr
 
+
 def calculator(num1, operation, num2):
     if operation == "add":
         return num1 + num2
@@ -19,13 +20,14 @@ def calculator(num1, operation, num2):
         return math.cos(num1)
     elif operation == "tan":
         return math.tan(num1)
-    
+    else:
+        return None
 
 demo = gr.Interface(
     fn=calculator,
     inputs=[
             gr.Number(value=4), 
-            gr.Radio(["add", "subtract", "multiply", "divide","square","cube","sin","cos","tan"]), 
+            gr.Radio(["add", "subtract", "multiply", "divide", "square", "cube", "sin", "cos", "tan"]), 
             "number"
             ],
     outputs="number",
@@ -39,4 +41,4 @@ demo = gr.Interface(
     description="Here's a sample scientific calculator. Enjoy! Code by: Freddy Aboulton   Improved by: Usually3"
 )
 
-demo.launch()
+demo.launch()