Python Flask Type Error when returning SQLAlchemy query result

I run a query to populate a on a web form. The is working. I click submit, which should POST the selection back to Flask, which runs a query on it. I am getting TypeError: Object of type BaseQuery is not JSON serializable.

This part seems to work fine until I click "submit":

<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>

I think the issue is happening with this SQLAlchemy query:

@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)

This is the error:

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
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Solution

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

In this line Roomtable.query.filter() returns a BaseQuery object. You would want to use first() (which would then return a Roomtable object) to get the first query result.

Try this

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