在Python中检查函数的返回值

Question

I have a small function for database connection in Django as follows:

def db_connection(query_name):
    try:
        cursor = connection.cursor()
        cursor.execute(query_name)
        descr = cursor.description
        rows = cursor.fetchall()
        result = [dict(zip([column[0] for column in descr], row)) for row in rows]
        return result
    except Exception as e:
        return e 
    finally:
       cursor.close()

This function is used in my function views for Django rest framework to execute SQL queries.The general syntax is as follows:

@api_view(['GET'])
def foo_bar(request):
    ....
    ....
    ....
    query1 = "Select name from table"
    result = db_connection(query1)

    return Response(result, status=status.HTTP_200_OK)

However,what I need is to change the status value in the Response tuple depending on the return value of my db_connection function ie to return a 200 OK if no exception occurs else a 500. How can I check if the return value of a function is an exception ?

Answer 1

You are explicitly bypassing all the nice control flow that exceptions already give you. Don't do that.

If you just want a 500 to be returned, then don't catch the exception at all; just let it bubble up, Django's exception handling middleware will catch it and return a 500 response.

In any case, you should never catch the base Exception class; only catch the things you can actually deal with. And when you do catch an exception, you should actually deal with it; returning it instead of raising it is of no use whatsoever.

Answer 2

I would move the try catch block in the foo_bar function over the result = db_connection(query1) code and return a 500 status from there, along with some kind of errors dict which contains a message explaining why it failed. I say this because I'm assuming you are making a REST API which must always return an answer and not crash the normal django way.