How to add vertical line to plotly plot

Question

I am testing plotly express.

I have the latest version: 0.4.1

I am trying to plot the most basic chart in their tutorial but it's throwing an error:

import plotly.express as px

df = px.data.iris()
fig = px.scatter(df, x="petal_length", y="petal_width")
fig.add_vline(x=2.5, line_width=3, line_dash="dash", line_color="green")
fig.add_hrect(y0=0.9, y1=2.6, line_width=0, fillcolor="red", opacity=0.2)
fig.show()


AttributeError: 'Figure' object has no attribute 'add_vline'

Am I doing something wrong?

All I want to do is to get add_vline working.

It's the second example on the how-to guide here: https://plotly.com/python/horizontal-vertical-shapes/

Answer 1

As of plotly version 4.12, which you seem to not be running, you can add Horizontal and Vertical Lines and Rectangles. So for your case, just use:

fig.add_vline()

And there's nothing wrong with your code on my end. This exact snippet:

import plotly.express as px
df = px.data.iris()
fig = px.scatter(df, x="petal_length", y="petal_width")
fig.add_vline(x=2.5, line_width=3, line_dash="dash", line_color="green")
fig.add_hrect(y0=0.9, y1=2.6, line_width=0, fillcolor="red", opacity=0.2)
fig.show()

...produces this figure:

Which plotly version are you running?

Answer 2

To run the minimal example your package plotly has to be up to date as well as your package plotly.express.

import plotly.express as px

df = px.data.iris()
fig = px.scatter(df, x="petal_length", y="petal_width")
fig.add_hline(y=0.9)
fig.add_vrect(x0=0.9, x1=2)
fig.show()

I quote from the documentation you have shared.

add_hline, add_vline, add_hrect, and add_vrect is introduced in plotly 4.12.

Please bring your package on this or a newer version.