import numpy as np
import holoviews as hv
hv.extension('bokeh')
The HLines element is a type of annotation that can mark multiple lines along the y-axis. It accepts a list of y-coordinates and will draw a horizontal line at each location. This has the advantage over HLine of being able to draw multiple lines at once and also being able to get hover information for each of the line.
ys = np.random.normal(size=10)
hv.HLines(ys).opts(tools=['hover'], color='red', line_width=5)
For full documentation and the available style and plot options, use hv.help(hv.HLines).