Plot vertical lines in matplotlib within a given y range

Question

I'm using the following:

fig, ax = plt.subplots(figsize=(20, 10))

ax.set_ylim(bottom=0, top=10)
for i in range(4):
    ax.axvline(x=i, ymin=5, ymax=9, color="red", linewidth=40)

Which gives:

I would expect there to be a vertical line at each point from y = 5 to y = 9.

Answer 1

You should use matplotlib.pyplot.vlines, as suggested by BigBen in the comment:

for i in range(4):
    ax.vlines(x=i, ymin=5, ymax=9, color="red", linewidth=40)

Answer 2

If you look at the parameters for axvline, you see that ymin and ymax goes from 0 to 1. A fraction of your complete ylimit. https://matplotlib.org/stable/api/_as_gen/matplotlib.pyplot.axvline.html

So you need something like .5 to .9 or calculate the appropriate fractions.

fig, ax = plt.subplots(figsize=(20, 10))

ax.set_ylim(bottom=0, top=10)
for i in range(4):
    ax.axvline(x=i, ymin=.5, ymax=.9, color="red", linewidth=40)

Output: