How to add a line parallel to y axis in matplotlib?

Question

I want to draw a line at x=c #constant.

This should be pretty straightforward, but how can I do it?

Answer 1

You can use matplotlib.pyplot.axvline().

import matplotlib.pyplot as plt

plt.figure()
plt.axvline(x=0.2)
plt.axvline(x=0.5)
plt.show()

Answer 2

Using matplotlib.pyplot's axvline method:

import matplotlib.pyplot as plt

plt.axvline(x=0.5)

You can also set range for the y value:

plt.axvline(x=0.5, ymin=0.2, ymax=0.4)

Default value for ymin = 0 and ymax = 1.