如何在python和Streamlight中创建依赖的dropdownlist？

Question

根据答案of this post，我能够在应用所需过滤器后显示数据帧

我有一个Streamlight代码，可以显示多个下拉列表

1. 第一个dropdownlist具有列名称选项（其multiselection选项）
2. 其他下拉列表将包括 选定列

我想要的是，如果用户选择cat3，并且cat3没有loc2 我希望在第三个下拉列表中根据数据帧的记录只显示loc1和loc3

代码：

import numpy as np
import pandas as pd
import streamlit as st 

df =pd.DataFrame({
            "source_number":
             [11199,11328,11287,32345,12342,1232,13456,123244,13456],
             "location":          
             ["loc2","loc1","loc3","loc1","loc2","loc2","loc3","loc2","loc1"],
              "category": 
             ["cat1","cat2","cat1","cat3","cat3","cat3","cat2","cat3","cat2"],
             })  

is_check = st.checkbox("Display Data")
if is_check:
    st.table(df)


columns = st.sidebar.multiselect("Enter the variables", df.columns)

sidebars = {}
for y in columns:
    ucolumns=list(df[y].unique())
    print (ucolumns)

    sidebars[y]=st.sidebar.multiselect('Filter '+y, ucolumns)   

if bool(sidebars):
    L = [df[k].isin(v) if isinstance(v, list) 
         else df[k].eq(v) 
         for k, v in sidebars.items() if k in df.columns]
    
    df1 = df[np.logical_and.reduce(L)]
    st.table(df1)