返回 SQLAlchemy 查詢結果時 Python Flask 類型錯誤

Question

我運行查詢以在 web 表單上填充 a。 正在工作。 我單擊提交，它應該將選擇發布回 Flask，它運行一個查詢。 我收到 TypeError：BaseQuery 類型的 Object 不是 JSON 可序列化的。

這部分似乎工作正常，直到我點擊“提交”：

<form RoomSelectForm action = "#" method = "post">
        <p><label>Select Room</label>
        <select name="roomselect">
            {% for room in roomselect %}
                <option value="{{ room[0] }}">{{ room[0] }}</option>
            {% endfor %}
        </select>
    <input type ="submit" value ="Edit Room" onclick="toggleform()"></p>
</form>

我認為這個 SQLAlchemy 查詢正在發生問題：

@app.route("/editroom", methods=["POST"])
def edit_room_original_values():
    rm = request.form['roomselect']
    rmval = Roomtable.query.filter(Roomtable.room == rm)
    return dict(value=rmval)

這是錯誤：

TypeError
TypeError: Object of type BaseQuery is not JSON serializable

Traceback (most recent call last)
File "C:\Users\user1\AppData\Local\Programs\Python\Python38\Lib\site-packages\flask\app.py", line 2464, in __call__
return self.wsgi_app(environ, start_response)
File "C:\Users\user1\AppData\Local\Programs\Python\Python38\Lib\site-packages\flask\app.py", line 2450, in wsgi_app
response = self.handle_exception(e)
File "C:\Users\user1\AppData\Local\Programs\Python\Python38\Lib\site-packages\flask\app.py", line 1867, in handle_exception
reraise(exc_type, exc_value, tb)
File "C:\Users\user1\AppData\Local\Programs\Python\Python38\Lib\site-packages\flask\_compat.py", line 39, in reraise
raise value
File "C:\Users\user1\AppData\Local\Programs\Python\Python38\Lib\site-packages\flask\app.py", line 2447, in wsgi_app
response = self.full_dispatch_request()
File "C:\Users\user1\AppData\Local\Programs\Python\Python38\Lib\site-packages\flask\app.py", line 1953, in full_dispatch_request
return self.finalize_request(rv)
File "C:\Users\user1\AppData\Local\Programs\Python\Python38\Lib\site-packages\flask\app.py", line 1968, in finalize_request
response = self.make_response(rv)
File "C:\Users\user1\AppData\Local\Programs\Python\Python38\Lib\site-packages\flask\app.py", line 2112, in make_response
rv = jsonify(rv)
File "C:\Users\user1\AppData\Local\Programs\Python\Python38\Lib\site-packages\flask\json\__init__.py", line 370, in jsonify
dumps(data, indent=indent, separators=separators) + "\n",
File "C:\Users\user1\AppData\Local\Programs\Python\Python38\Lib\site-packages\flask\json\__init__.py", line 211, in dumps
rv = _json.dumps(obj, **kwargs)
File "C:\Users\user1\AppData\Local\Programs\Python\Python38\Lib\json\__init__.py", line 234, in dumps
return cls(
File "C:\Users\user1\AppData\Local\Programs\Python\Python38\Lib\json\encoder.py", line 201, in encode
chunks = list(chunks)
File "C:\Users\user1\AppData\Local\Programs\Python\Python38\Lib\json\encoder.py", line 431, in _iterencode
yield from _iterencode_dict(o, _current_indent_level)
File "C:\Users\user1\AppData\Local\Programs\Python\Python38\Lib\json\encoder.py", line 405, in _iterencode_dict
yield from chunks
File "C:\Users\user1\AppData\Local\Programs\Python\Python38\Lib\json\encoder.py", line 438, in _iterencode
o = _default(o)
File "C:\Users\user1\AppData\Local\Programs\Python\Python38\Lib\site-packages\flask\json\__init__.py", line 100, in default
return _json.JSONEncoder.default(self, o)
File "C:\Users\user1\AppData\Local\Programs\Python\Python38\Lib\json\encoder.py", line 179, in default
raise TypeError(f'Object of type {o.__class__.__name__} '
TypeError: Object of type BaseQuery is not JSON serializable
The debugger caught an exception in your WSGI application. You can now look at the traceback which led to the error.
To switch between the interactive traceback and the plaintext one, you can click on the "Traceback" headline. From the text traceback you can also create a paste of it. For code execution mouse-over the frame you want to debug and click on the console icon on the right side.

You can execute arbitrary Python code in the stack frames and there are some extra helpers available for introspection:

dump() shows all variables in the frame
dump(obj) dumps all that's known about the object

Answer 1

rmval = Roomtable.query.filter(Roomtable.room == rm)

在這一行Roomtable.query.filter()返回一個BaseQuery object。 您可能希望使用first() （然后返回Roomtable對象）來獲取第一個查詢結果。

嘗試這個

rmval = Roomtable.query.filter(Roomtable.room == rm).first()

Answer 2

該查詢是一種需要傳入 class 的方法，因此它知道將過濾結果返回為：

rmval = Roomtable.query(Room).filter(Roomtable.room == rm)

假設 Room 為 class。