Streamlit美国州城联动下拉框问题：字典显示异常

核心问题修正点 #

当前代码用states_dict.items()作为州下拉框选项，导致显示(州全名, 州缩写)的键值对，需调整为仅显示州全名，同时保留全名到缩写的映射用于城市筛选；另外回调函数调用方式有误，城市列表初始化逻辑也需优化避免重复追加数据。

修改后的完整代码 #

import streamlit as st
import geonamescache

col1, col2, col3 = st.columns(3)

with col2:
    gc = geonamescache.GeonamesCache()
    cities = gc.get_cities()
    us_states = gc.get_us_states()

    # 初始化session状态
    if "disabled" not in st.session_state:
        st.session_state.disabled = True

    def callback():
        st.session_state.disabled = False

    # --- 处理州数据：建立州全名到缩写的映射，生成仅含全名的选项列表 ---
    state_name_to_code = {code['name']: state for state, code in us_states.items()}
    state_options = ["Select a State"] + list(state_name_to_code.keys())

    # 州下拉选择框：仅显示州全名
    selected_state_name = st.selectbox("Select a State", state_options)

    if selected_state_name != "Select a State":
        st.write("You selected:", selected_state_name)
        # 获取选中州的缩写
        selected_state_code = state_name_to_code[selected_state_name]
    else:
        st.write("#")
        selected_state_code = None

    # --- 处理城市数据：根据选中州的缩写筛选 ---
    city_options = ["Select a city"]
    if selected_state_code:
        for city in cities.values():
            if city['countrycode'] == 'US' and city['admin1code'] == selected_state_code:
                city_options.append(city['name'])

    # 城市下拉选择框：仅当选中州后启用
    selected_city = st.selectbox(
        "Select a city", 
        city_options, 
        disabled=st.session_state.disabled, 
        on_change=callback  # 传入函数名而非直接调用
    )

    if selected_city != "Select a city":
        st.write("You selected:", selected_city)
    else:
        st.write("#")

关键改动说明 #

• 州数据处理：
  • 构建state_name_to_code字典，实现州全名到缩写的快速映射
  • 生成state_options列表，默认选项加所有州全名，确保下拉框仅显示州全名
• 城市筛选逻辑：
  • 将城市列表初始化移到州选择之后，每次选州都重新生成对应城市列表，避免重复追加旧数据
  • 仅在选中有效州时，用对应缩写筛选美国城市
• 回调函数修正：
  • on_change参数传入函数名callback而非callback()，后者会直接执行函数，前者才是触发选择变化时调用

内容的提问来源于stack exchange，提问作者Nicholas Cordone