如何消除Plotly子图中的重复图例（Python）

当使用Plotly子图布局时，若不同子图包含相同名称的trace，会导致右侧出现重复图例。以下是两种有效的解决方法：

原始问题代码 #

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

f1 = go.Figure([
    go.Scatter(x=[1, 2, 3, 4, 5], y=[1, 2, 3, 4, 5], name="A"),
    go.Scatter(x=[1, 2, 3, 4, 5], y=[5, 4, 3, 2, 1], name="B")
])
f2 = go.Figure([
    go.Scatter(x=[1, 2, 3, 4, 5], y=[1, 2, 5, 4, 5], name="B"),
    go.Scatter(x=[1, 2, 3, 4, 5], y=[5, 4, 1, 2, 1], name="C")
])

fig = make_subplots(rows=1, cols=2, subplot_titles=['F1', 'F2'])

for ea in f1.data:
    fig.add_trace(ea, row=1, col=1)
    
for ea in f2.data:
    fig.add_trace(ea, row=1, col=2)
    
fig.show()

重复图例效果：

方法一：自动去重图例 #

通过记录已出现的图例名称，仅保留每个名称的第一次显示，后续同名trace隐藏图例：

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

f1 = go.Figure([
    go.Scatter(x=[1,2,3,4,5], y=[1,2,3,4,5], name="A"),
    go.Scatter(x=[1,2,3,4,5], y=[5,4,3,2,1], name="B")
])
f2 = go.Figure([
    go.Scatter(x=[1,2,3,4,5], y=[1,2,5,4,5], name="B"),
    go.Scatter(x=[1,2,3,4,5], y=[5,4,1,2,1], name="C")
])

fig = make_subplots(rows=1, cols=2, subplot_titles=['F1', 'F2'])
seen_names = set()

# 添加第一个子图的trace
for ea in f1.data:
    if ea.name not in seen_names:
        seen_names.add(ea.name)
    else:
        ea.showlegend = False
    fig.add_trace(ea, row=1, col=1)

# 添加第二个子图的trace
for ea in f2.data:
    if ea.name not in seen_names:
        seen_names.add(ea.name)
    else:
        ea.showlegend = False
    fig.add_trace(ea, row=1, col=2)

fig.show()

方法二：使用图例分组（推荐） #

通过legendgroup将同名trace归为一组，手动设置仅显示一次图例，同时保证点击图例时同组trace联动：

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

f1 = go.Figure([
    go.Scatter(x=[1,2,3,4,5], y=[1,2,3,4,5], name="A", legendgroup="A"),
    go.Scatter(x=[1,2,3,4,5], y=[5,4,3,2,1], name="B", legendgroup="B")
])
f2 = go.Figure([
    # 同名trace隐藏图例，指定同一图例组
    go.Scatter(x=[1,2,3,4,5], y=[1,2,5,4,5], name="B", legendgroup="B", showlegend=False),
    go.Scatter(x=[1,2,3,4,5], y=[5,4,1,2,1], name="C", legendgroup="C")
])

fig = make_subplots(rows=1, cols=2, subplot_titles=['F1', 'F2'])

for ea in f1.data:
    fig.add_trace(ea, row=1, col=1)
    
for ea in f2.data:
    fig.add_trace(ea, row=1, col=2)
    
fig.show()

内容的提问来源于stack exchange，提问作者Scoodood