Filling between intervals on plot based on pandas column value

I have an example DataFrame:

df = 

segment       sample      data_value
first           1            28
first           2            53
first           3            19
second          4            50
second          5            39
second          6            61
third           7            22
third           8            49
third           9            34            

I'd like to plot data_value vs. sample with plot shading (with the background of the plot indicating each segment with a different color. For example, from the bottom of the graph to the top, shading the background of the plot for the "first" segment as blue, "second" segment as green, etc. with the legend.

I can do:

plt.scatter(df['sample'], df['data_value'])

but am struggling on how to fill the backgrounds for each segment of the plot in a color-coded way to show the progression over time. Could I use fill_between() somehow?

Any help would be awesome. Thanks!

Is this what you are looking for? As suggested by JohanC, you can use axhspan to create bands as shown below...

Note: I am assuming that the order of sample is ascending, so that the code will work...

plt.scatter(df['data_value'], df['sample'])
colors = ['blue', 'green', 'red']
start = 0
for i, segs in enumerate(df.segment.unique()):
    plt.axhspan(start, df[df.segment == segs]['sample'].max(), facecolor=colors[i], alpha=0.2)
    start=df[df.segment == segs]['sample'].max()

Plot