Update backend.py

backend.py

@@ -1,9 +1,9 @@
-from fastapi import FastAPI, HTTPException
+from fastapi import APIRouter, HTTPException
 from pydantic import BaseModel, field_validator
 import math
 import re
 
-app = FastAPI()
+router = APIRouter()
 
 ALLOWED_FUNCTIONS = {'sin', 'cos', 'tan', 'log', 'ln', 'sqrt', 'abs', 'pow'}
 ALLOWED_CONSTANTS = {'pi', 'e'}
@@ -31,7 +31,7 @@ class Expression(BaseModel):
         
         return v
 
-@app.post("/calculate")
+@router.post("/calculate")
 async def calculate_api(expression: Expression):
     try:
         result = evaluate_expression(expression.expr)
@@ -57,8 +57,4 @@ def evaluate_expression(expr: str) -> float:
     except ValueError as e:
         raise ValueError(f"Math domain error: {str(e)}")
     except Exception as e:
-        raise ValueError(f"Invalid expression: {str(e)}")
-
-if __name__ == "__main__":
-    import uvicorn
-    uvicorn.run(app, host="0.0.0.0", port=8000)
+        raise ValueError(f"Invalid expression: {str(e)}")