Add text for different part of line chart plot in plotly python

• I have simulated data with features that will generate a graph similar to one you have shown
• there are three ways to add labels
  1. labels against traces in legend
  2. as additional scatter plots with mode="text"
  3. as annotations on the figure

All three of these are demonstrated below. It does assume you have a working knowledge of pandas

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

df = pd.DataFrame({"AAA":np.concatenate([np.random.uniform(1,5,20), np.full(20,np.nan)]), 
              "BBB":np.concatenate([np.full(20,np.nan), np.random.uniform(1,5,20), ])})

# create two traces, where traces are in legend to label AAA & BBB
fig = px.scatter(df, x=df.index, y=["AAA","BBB"]).update_traces(mode="lines+markers")

# additionally create text trace, that are last AAA & BBB
lastAAA = df.loc[~df["AAA"].isna()].iloc[-1]
lastBBB = df.loc[~df["BBB"].isna()].iloc[-1]
fig.add_trace(go.Scatter(x=[lastAAA.name], y=[lastAAA["AAA"]], text="AAA", mode="text", showlegend=False))
fig.add_trace(go.Scatter(x=[lastBBB.name], y=[lastBBB["BBB"]], text="BBB", mode="text", showlegend=False))

# additionally add annotations
fig.add_annotation(x=lastAAA.name, y=lastAAA["AAA"], text="AAA")
fig.add_annotation(x=lastBBB.name, y=lastBBB["BBB"], text="BBB")