跟随这里的回答 https://stackoverflow.com/questions/71610356/how-to-specify-the-x-coordinate-on-a-grouped-bar-chart-on-plotly
我想要以编程方式获取所有的x坐标。
我可以通过调整硬编码的数字来获得工作解决方案，例如：
    import plotly.express as px
    import plotly.graph_objects as go
    import numpy as np
    
    df = px.data.tips()
    print(df.head())
    fig = px.histogram(
        df, x="sex", y="total_bill", color="time", barmode="group", height=400
    )
    
    # 添加覆盖分类x轴的次要x轴
    fig.layout.xaxis2 = go.layout.XAxis(
        overlaying='x', range=[0, 2], showticklabels=False)
    
    # 添加线条跟踪，并与第二个x轴关联
    bargap = 0.2
    for i in range(2):
        x = bargap/2 + (1-bargap)/4
        y = [1111]
        print(111,x, y)
        scatt = fig.add_scatter(x=[i+x], y=y, xaxis='x2',
                                showlegend=False, line={'color': 'gray'})
        x *=2.3
        print(22222,x, y)
        scatt = fig.add_scatter(x=[i+x], y=y, xaxis='x2',
                                showlegend=False, line={'color': 'gray'})
    fig
但我需要一个动态解决方案，当我将颜色更改为“day”时也能正常工作：
    fig = px.histogram(
        df, x="sex", y="total_bill", color="day", barmode="group", height=400
    )
然后在子图中有4个框。在我处理的数据中，总是有不同数量的图和子图。
我真的希望plotly的开发人员能够帮助解决这个问题，这是我在使用plotly时遇到的第一个主要限制。

import plotly.express as px
df = px.data.tips()
# Use primary and secondary in your function to vary
primary = 'day'
secondary = 'sex'
fig = px.histogram(df, x=primary, y="total_bill", color=secondary, barmode="group", height=400)
nPri = len(df[primary].unique())
nSec = len(df[secondary].unique())
N = nPri
# Group centers
xrange = N-1  # the underlying x-axis is scaled with N automatically
xGp = [xrange * n / (N-1) for n in range(N)]
# Plot group centers
for ix in xGp:
    fig.add_vline(x=ix)
bargap = 0.2  # I tried it with some variation. Still works.
fig.layout.bargap = bargap
# Calculate bar sizing
gpWidth = 1 - bargap
barWidth = gpWidth / nSec
# Left and right edges of each group
gpEdges = [(x - gpWidth / 2, x + gpWidth / 2) for x in xGp]
for ix1, ix2 in gpEdges:
    gpRange = ix2 - ix1 # group range
    xB = [ix1 + barWidth/2 + barWidth * n for n in range(nSec)]  # list of x coordinates of each bar in the group
    print(xB)
    for x in xB:
        fig.add_vline(x=x, line_color='blue')
fig.show()