我正在开发一个 Flask 应用程序，用于过滤 Mysql 数据库表的值，并根据第一个下拉列表的选定值，它将更新第二个下拉列表的值。最后返回一些数据

现在代码正在工作，但代码中似乎存在错误，这样当我从第一个下拉列表中进行新选择时，它将用第一个下拉列表的值以及预期的值填充第二个下拉列表第二个下拉列表的值

它不应该这样做，我希望它只用预期值填充第二个下拉列表，而不是将第一个下拉列表的值与其一起添加。

这是我的烧瓶应用程序代码：

from flask import jsonify, request
from flask import Flask, render_template  
import mysql.connector

app = Flask(__name__)

# Configure MySQL connection
cnx = mysql.connector.connect(
  host="xxxxxxx",
  user="xxxxxxxxx",
  password="xxxxxxxxx",
  database="xxxxxxxxxx")


@app.route('/', methods=['GET', 'POST'])
def index():
    try:
        cursor = cnx.cursor()
        query = "SELECT topic FROM text_table"
        cursor.execute(query)
        data = [row[0] for row in cursor.fetchall()] # Get the first column of all rows
        cursor.nextset() # consume any unread result
        cursor.close()


        if request.method == 'POST':
            selected_topic = request.form.get('selected_topic') # Get the selected topic from the form
            if selected_topic:
                cursor = cnx.cursor()
                query = "SELECT sub_topic FROM text_table WHERE topic = %s"
                cursor.execute(query, (selected_topic,))
                sub_topics = [row[0] for row in cursor.fetchall()] # Get the sub topics for the selected topic
                cursor.nextset()
                selected_sub_topic = request.form.get('selected_sub_topic') # Get the selected sub topic from the form
                if selected_sub_topic:
                    query = "SELECT text FROM text_table WHERE topic = %s AND sub_topic = %s"
                    cursor.execute(query, (selected_topic, selected_sub_topic))
                    result = cursor.fetchone()[0] # Get the value of the text for the selected sub topic
                    cursor.nextset()
                    cursor.close()
                    return render_template('index.html', topics=data, selected_topic=selected_topic, sub_topics=sub_topics, selected_sub_topic=selected_sub_topic, result=result)

                cursor.close()
                return render_template('index.html', topics=data, selected_topic=selected_topic, sub_topics=sub_topics)

        return render_template('index.html', topics=data)

    except Exception as e:
        # Return an error message if there's an exception
        return jsonify(error=str(e)), 500


if __name__ == '__main__':
    app.run()

这是我的 html 代码，带有一点 JavaScript

  
    
    
  
  
    

      
        {% for topic in topics %}
          
            {{ topic }}
          
        {% endfor %}
      
      
        {% for sub_topic in sub_topics %}
          
            {{ sub_topic }}
          
        {% endfor %}
      
      
    
    {% if result %}
      
{{ result }}
    {% endif %}
  

谢谢，任何帮助将不胜感激