fun.py

# passing functions in functions

def fun(arg):
    arg()

def fun2():
    print('fun2')

# decorator function

def decorator(fun):
    def wrapper(*args, **kwargs):
      
        nums = args[:-1]
        for arg in nums:
            try:
                int(arg)
            except ValueError:
                return {'message': 'Invalid input'}

        tu=tuple(map(int, nums))
        tu = tu + (args[-1],)
        return fun(*tu, **kwargs)

    return wrapper

@decorator
def simpleArith(num1, num2, operator):
 
    if operator == '+':
        return {"result": num1 + num2}
    elif operator == '-':
        return {"result": num1 - num2}
    elif operator == '*':
        return{"result": num1 * num2}
    elif operator == '/':
        return {"result": num1 / num2}

@decorator
def complexArith(num1, num2, num3, operator):

    if operator == '+':
        return {"result": num1 + num2 + num3}
    elif operator == '-':
        return {"result": num1 - num2 - num3}
    elif operator == '*':
        return {"result": num1 * num2 * num3}
    elif operator == '/':
        return {"result": num1 / num2 / num3}

print(simpleArith('1', 2, '+'))