我有麻烦将日期从HTML转换成Python字符串，以便在查询中使用它

我想用日期参数向MySQL发送查询。

roomList=Room.objects.raw(
             "select room.id "
 +"from room join client_room on room.id=client_room.room_id "
 +"where client_room.date_in>'"+request.GET.get("date_out")+ ..."#argument-date_out

我从HTML接收日期

            <p>
                <label>Enter first date</label><br>
                <input type="date" name="date_in" value="{{date1}}"/>
            </p>
            <p>
                <label>Enter second date</label><br>
                <input type="date" name="date_out" value="{{date2}}"/>
            </p>

当单独打印日期时，它可以正确地打印

print(request.GET.get("date_in"))
2021-04-01#Terminal

但如果尝试赋值和/或串联，则返回非类型

date=request.GET.get("date_in")
print("Date is " + date)
can only concatenate str (not "NoneType") to str #HTML Response