如何将Plotly图例符号从线条修改为方形？

你可以通过两种简单方式实现将图例符号从线条改为方形：

方法1：添加trace时单独设置图例符号 #

在创建go.Scatter对象时，直接添加legend_symbol="square"参数，指定该trace的图例符号为方形：

import pandas as pd
import plotly.express as px
import plotly.graph_objects as go

def save_fig(fig,pngname):
    fig.write_image(pngname,format="png",width=600,height=400, scale=1)
    print("[[%s]]"%pngname)
    return

df = px.data.stocks()
df = df[['date','AMZN', 'AAPL']]

fig = go.Figure()
for name in df.columns:
    if name == 'date': continue
    trace = go.Scatter(
        x = df['date'],
        y = df[name],
        name=name,
        legend_symbol="square"  # 设置图例符号为方形
    )
    fig.add_trace(trace)
        
save_fig(fig,"./demo.png")

方法2：批量更新所有trace的图例符号 #

如果已经创建完所有trace，可通过fig.update_traces()方法统一修改所有图例符号，无需逐个调整：

import pandas as pd
import plotly.express as px
import plotly.graph_objects as go

def save_fig(fig,pngname):
    fig.write_image(pngname,format="png",width=600,height=400, scale=1)
    print("[[%s]]"%pngname)
    return

df = px.data.stocks()
df = df[['date','AMZN', 'AAPL']]

fig = go.Figure()
for name in df.columns:
    if name == 'date': continue
    trace = go.Scatter(
        x = df['date'],
        y = df[name],
        name=name,
    )
    fig.add_trace(trace)

# 统一设置所有trace的图例符号为方形
fig.update_traces(legend_symbol="square")
        
save_fig(fig,"./demo.png")

补充说明：legend_symbol参数支持多种符号取值，比如circle、diamond等，可根据需求替换。

内容的提问来源于stack exchange，提问作者lucky1928