How to Label Lines in Matplotlib

1. Label Lines With the label Parameter in Matplotlib
2. Set Label/Legend Positions With the loc Parameter in Matplotlib

This tutorial will demonstrate how to label lines in Matplotlib and place them inside the plot.

Before working with plots, we need to set up our script to work with the library. So we start by importing matplotlib.

Furthermore, we load the randrange function from the random module to quickly generate some data. Remember that it will look different for you.

import matplotlib.pyplot as plt
from random import randrange

data_1 = [randrange(0, 10) for _ in range(0, 10)]

Label Lines With the label Parameter in Matplotlib

We label lines or other kinds of plots with the label parameter, which we provide with a string. But for the label to show, we also have to call the legend function.

plt.plot(data_1, label="Random Data")

plt.legend()

plt.show()

Output:

Set Label/Legend Positions With the loc Parameter in Matplotlib

It is also possible to set the position of the legend. We do this with the loc parameter of the legend method.

plt.legend(loc="lower left")

Output:

The following positions are valid arguments:

upper right
upper left
lower left
lower right
right
center left
center right
lower center
upper center
center

Complete code:

import matplotlib.pyplot as plt
from random import randrange

data_1 = [randrange(0, 10) for _ in range(0, 10)]
data_2 = [randrange(0, 10) for _ in range(0, 10)]

plt.plot(data_1, label="Random Data")

plt.legend(loc="lower left")

plt.show()