You can use the following syntax to draw a vertical line in Matplotlib:

import matplotlib.pyplot as plt #draw vertical line at x=2 plt.axvline(x=2)

The following examples show how to use this syntax in practice with the following pandas DataFrame:

**import pandas as pd
#create DataFrame
df = pd.DataFrame({'x': [1, 2, 3, 4, 5, 6, 7, 8],
'y': [5, 7, 8, 15, 26, 39, 45, 40]})
#view DataFrame
df
x y
0 1 5
1 2 7
2 3 8
3 4 15
4 5 26
5 6 39
6 7 45
7 8 40
**

**Example 1: Draw One Vertical Line**

The following code shows how to draw one vertical line on a Matplotlib plot:

**import matplotlib.pyplot as plt
#create line plot
plt.plot(df.x, df.y)
#add vertical line at x=2
plt.axvline(x=2, color='red', linestyle='--')**

**Example 2: Draw Multiple Vertical Lines**

The following code shows how to draw multiple vertical lines on a Matplotlib plot:

**import matplotlib.pyplot as plt
#create line plot
plt.plot(df.x, df.y)
#add vertical line at x=2
plt.axvline(x=2, color='red', linestyle='--')
#add vertical line at x=4
plt.axvline(x=4, color='black', linestyle='-')
**

**Example 3: Draw Multiple Vertical Lines with Legend**

The following code shows how to draw multiple vertical lines on a Matplotlib plot and add a legend to make the lines easier to interpret:

**import matplotlib.pyplot as plt
#create line plot
plt.plot(df.x, df.y)
#add vertical line at x=2
plt.axvline(x=2, color='red', linestyle='--', label='First Line')
#add vertical line at x=4
plt.axvline(x=4, color='black', linestyle='-', label='Second Line')
#add legend
plt.legend()**

**Note:** Refer to the Matplotlib documentation for a list of potential colors and linestyles you can apply to vertical lines.

**Additional Resources**

How to Draw a Horizontal Line in Matplotlib

How to Plot Multiple Lines in Matplotlib

How to Plot a Time Series in Matplotlib

How to Draw Rectangles in Matplotlib

How to Draw Arrows in Matplotlib