separated model, better type for `operation`

app.py

@@ -1,31 +1,28 @@
 # main.py
 import gradio as gr
 from fastapi import FastAPI, HTTPException
-from pydantic import BaseModel
+
+from models import CalculationRequest
 
 # FastAPI setup
 app = FastAPI()
 
-class CalculationRequest(BaseModel):
-    operation: str
-    x: float
-    y: float
 
 @app.post("/calculate")
 def calculate(request: CalculationRequest):
+    operation = request.operation.value
+    
     try:
-        if request.operation == "add":
+        if operation == "add":
             answer = request.x + request.y
-        elif request.operation == "subtract":
+        elif operation == "subtract":
             answer = request.x - request.y
-        elif request.operation == "multiply":
+        elif operation == "multiply":
             answer = request.x * request.y
-        elif request.operation == "divide":
+        else: # only option left is divide
             if request.y == 0:
                 raise HTTPException(status_code=400, detail="Division by zero is not allowed")
             answer = request.x / request.y
-        else:
-            raise HTTPException(status_code=400, detail="Invalid operation")
         
         return {"result": answer}
     except ValueError:

models.py

@@ -0,0 +1,16 @@
+from enum import Enum
+
+from pydantic import BaseModel
+
+
+class Operation(Enum):
+    ADD = "add"
+    SUBTRACT = "subtract"
+    MULTIPLY = "multiply"
+    DIVIDE = "divide"
+
+
+class CalculationRequest(BaseModel):
+    operation: Operation
+    x: float
+    y: float