Plotly子图：如何为各子图添加独立图例并自定义柱状图尺寸

一、为每个子图添加对应独立图例 #

默认情况下Plotly会将所有图例集中显示，要实现每个子图绑定专属图例，需通过以下配置实现：

核心配置要点 #

• 为每个子图的所有trace设置相同的legendgroup，用于关联到同一个图例组
• 在布局中定义多个独立图例，通过xref/yref绑定到目标子图，调整x/y坐标控制图例位置
• 关闭全局统一图例，让每个trace仅显示对应组的图例

二、自定义柱状图尺寸 #

可以从两个层面调整：

• 单根柱子宽度：给Bar trace添加marker={"width": 0.5}参数（数值范围0-1，越小柱子越窄）
• 子图区域大小：在make_subplots中通过column_widths和row_heights设置子图的宽高占比，比如column_widths=[0.6, 0.4]让第一列子图更宽

修改后的完整代码 #

import plotly.express as px
import plotly.graph_objects as go
from plotly.subplots import make_subplots

# 调整子图宽高比例，影响柱状图显示区域
specs = [[{'type':'pie'}, {"type": "pie"}], [{"type": "bar"}, {"type": "bar"}]]
fig = make_subplots(
    rows=2, cols=2, 
    specs=specs, 
    shared_yaxes=True,
    subplot_titles=['Pie Chart A', 'Pie Chart B', 'Bar Chart A', ''],
    column_widths=[0.5, 0.5],  # 自定义列宽比例
    row_heights=[0.5, 0.5]     # 自定义行高比例
)

# 饼图1：绑定到图例组pie_1
df1 = df['Generation'].value_counts().reset_index(name='count')
fig.add_trace(go.Pie(
    labels=df1['index'], 
    values=df1['count'],
    hole=0.6,
    marker_colors=['#353837','#646665', '#8e9492'],
    textinfo='percent + value + label',
    textposition=['inside', 'inside','outside'],
    legendgroup="pie_1",  # 绑定图例组
    showlegend=True
), 1, 1)  

# 饼图2：绑定到图例组pie_2
df2 = df['Education_Level'].value_counts().reset_index(name='count')
fig.add_trace(go.Pie(
    labels=df2['index'], 
    values=df2['count'],
    hole=0.6,
    marker_colors=['#353837','#646665', '#8e9492','#acadac','#f0f2f0'],
    textinfo='percent + value + label',
    textposition=['inside', 'inside','inside','inside','outside'],
    legendgroup="pie_2",  # 绑定图例组
    showlegend=True
), 1, 2)  

df4 = df.groupby(['Generation'])['Education_Level'].value_counts().reset_index(name='count')
df4['%'] = 100 * df4['count'] / df4.groupby(['Generation'])['count'].transform('sum')

# 柱状图trace：统一绑定到图例组bar_1，同时自定义柱子宽度
trace1 = go.Bar(
    x=df4[df4['Generation']=='Millenials']['Education_Level'],
    y=df4[df4['Generation']=='Millenials']['count'],
    name='Millenials',
    text=['M, {}, {:.0%}'.format(v, p/100) for v,p in zip(
        df4[df4['Generation']=='Millenials']['count'],  
        df4[df4['Generation']=='Millenials']['%']
    )],
    textposition=['inside', 'inside', 'inside', 'inside', 'outside'],
    textfont_size=15,
    marker_color=['#455f66']*len(df4['Education_Level']),
    marker={"width": 0.4},  # 自定义柱子宽度
    legendgroup="bar_1",    # 绑定图例组
    showlegend=True
)

trace2 = go.Bar(
    x=df4[df4['Generation']=='Generation X']['Education_Level'],
    y=df4[df4['Generation']=='Generation X']['count'],
    name='Generation X',
    text=['GX, {}, {:.0%}'.format(v, p/100) for v,p in zip(
        df4[df4['Generation']=='Generation X']['count'],  
        df4[df4['Generation']=='Generation X']['%']
    )],
    textposition=['inside', 'inside', 'inside', 'outside', 'outside'],
    textfont_size=15,
    marker_color=['#7da8b3']*len(df4['Education_Level']),
    marker={"width": 0.4},
    legendgroup="bar_1",
    showlegend=True
)

trace3 = go.Bar(
    x=df4[df4['Generation']=='Boomers']['Education_Level'],
    y=df4[df4['Generation']=='Boomers']['count'],
    name='Boomers',
    text=['B, {}, {:.0%}'.format(v, p/100) for v,p in zip(
        df4[df4['Generation']=='Boomers']['count'],  
        df4[df4['Generation']=='Boomers']['%']
    )],
    textfont_size=15,
    textposition='outside',
    marker_color=['#9bd9e8']*len(df4['Education_Level']),
    marker={"width": 0.4},
    legendgroup="bar_1",
    showlegend=True
)

fig.append_trace(trace1,2,1)
fig.append_trace(trace2,2,1)
fig.append_trace(trace3,2,1)

fig.update_annotations(font_size=12)
fig.update_layout(
    height=650,
    width=850,
    showlegend=False,  # 关闭全局图例
    title=dict(
        text="<b> [Summary] </b> Highlevel Overview ",
        font=dict(family="Arial", size=20, color='#283747')
    ),
    # 定义三个独立图例，分别绑定到对应子图
    legends=[
        # 饼图1的图例
        dict(
            legendgroup="pie_1",
            x=0.25, y=1.05,  # 位置调整
            xref="x1", yref="paper",
            orientation="h"
        ),
        # 饼图2的图例
        dict(
            legendgroup="pie_2",
            x=0.75, y=1.05,
            xref="x2", yref="paper",
            orientation="h"
        ),
        # 柱状图的图例
        dict(
            legendgroup="bar_1",
            x=0.5, y=-0.1,
            xref="paper", yref="paper",
            orientation="h"
        )
    ]
)

fig.show()

内容的提问来源于stack exchange，提问作者WF30