Plotly Python使用按钮过滤数据点击下拉框后数值异常问题问询

问题原因 #

你代码的核心问题是visible参数对应的布尔列表长度和图表实际包含的trace数量不匹配：

• 每个国家对应2条Bar trace（Coal、Gas各1条），3个国家总共生成了6条trace
• 原有代码构造的显隐控制列表args = [False] * len(df_dict)长度仅为3，和6条trace的数量不匹配，点击下拉按钮时仅能控制前3条trace的显隐，剩余trace的显隐逻辑完全错误，最终导致切换国家后图表数值不符合预期。

修复方案 #

调整显隐控制列表的构造逻辑，保证其长度和总trace数一致，对应每个国家的2条trace同步控制显隐即可，修正后的完整代码如下：

import pandas as pd
import plotly.graph_objects as go

#Dummy data
df_germany = pd.DataFrame({'Fuels':[2010,2011],'Coal':[200,250],'Gas':[400,500]})
df_poland = pd.DataFrame({'Fuels':[2010,2011],'Coal':[500,150],'Gas':[600,100]})
df_spain = pd.DataFrame({'Fuels':[2010,2011],'Coal':[700,260],'Gas':[900,400]})

#put dataframes into object for easy access:
df_dict = {'Germany': df_germany, 
           'Poland': df_poland, 
           'Spain': df_spain}

#每个国家对应的trace数量，此处为2种燃料
trace_per_country = len(df_germany.columns) -1
#总trace数量
total_trace = len(df_dict) * trace_per_country

#create a figure from the graph objects (not plotly express) library
fig = go.Figure()

buttons = []
i = 0

#iterate through dataframes in dict
for country, df in df_dict.items():
    #iterate through columns in dataframe (not including the year column)
    for column in df.drop(columns=['Fuels']):
        #add a bar trace to the figure for the country we are on
        fig.add_trace(go.Bar(
                          name = column,
                          #x axis is "fuels" where dates are stored as per example
                          x = df.Fuels.to_list(),
                          #y axis is the data for the column we are on
                          y = df[column].to_list(),
                          #setting only the first country to be visible as default
                          visible = (i==0)
                        )
                     )
        
    #args长度改为总trace数，初始全为False
    args = [False] * total_trace
    #将当前国家对应的2个trace设为可见
    args[trace_per_country*i : trace_per_country*(i+1)] = [True]*trace_per_country
    
    #create a button object for the country we are on
    button = dict(label = country,
                  method = "update",
                  args=[{"visible": args}])
    
    #add the button to our list of buttons
    buttons.append(button)
    
    #i is an iterable used to tell our "args" list which value to set to True
    i+=1
        
fig.update_layout(
    updatemenus=[
        dict(
        #change this to "buttons" for individual buttons
        type="dropdown",
        #this can be "left" or "right" as you like
        direction="down",
        #(1,1) refers to the top right corner of the plot
        x = 1,
        y = 1,
        #the list of buttons we created earlier
        buttons = buttons)
    ],
    #stacked bar chart specified here
    barmode = "stack",
    #so the x axis increments once per year
    xaxis = dict(dtick = 1))

fig.show()

运行修正后的代码，点击下拉按钮切换国家即可得到符合预期的堆叠柱状图。

内容的提问来源于stack exchange，提问作者Hongyi Chen