figure text label not working in line chart plotly python

Question

I am trying to create a line charts with text labels on the chart itself but it is not working. It is working perfectly fine in scatter plot with the text parameter which you can see below.

code -

import plotly.express as px

fig = px.scatter(crime2,
                 x='murder',
                 y='burglary',
                 size='population',
                 text='state')  # add figure label
fig.update_layout(xaxis_title='Murder Rate',
                  yaxis_title='Burglary Rate')
fig.update_traces(marker=dict(color='red'))
fig.show()

But it's not working with line chart. code for line chart -

fig = px.line(covid_subset,
              x='date',
              y='total_cases',
              color='location',
              text='location'
)
fig.update_layout(title='Cumulative Confirmed covid-19 cases')
fig.show()

As you can see instead of show the country label on the line chart only at one place it kept showing all over the line.

I might missing some parameter but I don't know what is it.

This is what I am trying to do -

Answer 1

Here's a slightly more compact/DRY alternative:

import plotly.express as px

df = px.data.gapminder().query("continent == 'Oceania'")

fig = px.line(df, x="year", y="lifeExp", color="country")
fig.for_each_trace(lambda t: fig.add_annotation(
    x=t.x[-1], y=t.y[-1], text=t.name, 
    font_color=t.line.color,
    ax=5, ay=0, xanchor="left", showarrow=False
))
fig.update_layout(showlegend=False)

fig.show()

Answer 2

This is actually how the parameter text is supposed to work: show a text all the time it appears on the given column. I have in mind two possible workarounds one with a trick and the other with annotations. These are not ideal solutions but you can start from here.

Get Data

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

url = "https://github.com/owid/covid-19-data/raw/master/public/data/owid-covid-data.csv"
df = pd.read_csv(url)

countries = ["Brazil", "Germany", "India", "Indonesia", "Italy",
             "Mexico", "New Zealand", "Norway", "South Africa",
             "South Korea", "United States"]

df = df[df["location"].isin(countries)].reset_index(drop=True)

Annotations

grp = df.groupby("location")[["date", "total_cases"]].last().reset_index()

annotations = []
for i, row in grp.iterrows():
    annotations.append(
    dict(x=row["date"],
         y=row["total_cases"],
         text=row["location"],
        xref="x",
        yref="y",
        showarrow=True,
#         arrowhead=7,
        ax=50,
        ay=0
        ))
    
    
fig = px.line(df,
              x='date',
              y='total_cases',
              color='location',
)
fig.update_layout(title='Cumulative Confirmed covid-19 cases',
                  title_x=0.5,
                  showlegend=False,
                  annotations=annotations)
fig.show()

Trick

df["date"] = df["date"].astype("M8")

grp = df.groupby("location")[["date", "total_cases"]]\
        .last().reset_index()
grp["text"] = grp["location"].copy()

grp["date"] = grp["date"] + pd.offsets.DateOffset(days=5)

df1 = pd.concat([df, grp], ignore_index=True, sort=False)\
        .sort_values(["location", "date"]).reset_index(drop=True)

df1["text"] = np.where(df1["text"].isnull(), "", df1["text"])

fig = px.line(df1,
              x='date',
              y='total_cases',
              color='location',
              text="text",
              hover_data={"text":False}
)
fig.update_traces(textposition='top center') 
fig.update_layout(title='Cumulative Confirmed covid-19 cases',
                  title_x=0.5,
                  showlegend=False,)
fig.show()