The trick to plot a donut chart using matplotlib is to draw a pie plot and add a white circle in the middle of it. In order to draw a circle, you can use the `Circle()`

function of matplotlib. The parameters passed to the function in the example below are:

`(x,y)`

: center point of the circle`radius`

: radius of the circle`color`

: color of the circle

In the example, the `add_artist()`

function is used to add the white circle on the axes of the pie chart. In order to get the current axes instance on the current figure, the `gca()`

function is used and to get the current figure, the `gcf()`

function is used.

```
# library
import matplotlib.pyplot as plt
# create data
size_of_groups=[12,11,3,30]
# Create a pie plot
plt.pie(size_of_groups)
#plt.show()
# add a white circle at the center
my_circle=plt.Circle( (0,0), 0.7, color='white')
p=plt.gcf()
p.gca().add_artist(my_circle)
# show the graph
plt.show()
```