Change the legend format of Python histogram

Question

I label the two different histograms in the same figure, as shown below. However, the legend for the two histograms are in the format of a box. I tried various ways to change the box to line but all did not work. I wonder how to implement such function?

Answer 1

One way to go about doing this is to specify explicitly the legend handles by hand:

handle1 = matplotlib.lines.Line2D([], [], c='r')
handle2 = matplotlib.lines.Line2D([], [], c='b')
plt.legend(handles=[handle1, handle2])

Depending of course a good deal on how you set everything up, this might look as follows:

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.lines import Line2D

# Generate some data that sort of looks like that in the question
np.random.seed(0)
x1 = np.random.normal(2, 1, 200)
x2 = np.random.exponential(1, 200)

# Plot the data as histograms that look like unfilled lineplots
fig = plt.figure()
ax = fig.add_subplot(111)
ax.hist(x1, label='target', histtype='step')
ax.hist(x2, label='2nd halo', histtype='step')

# Create new legend handles but use the colors from the existing ones
handles, labels = ax.get_legend_handles_labels()
new_handles = [Line2D([], [], c=h.get_edgecolor()) for h in handles]

plt.legend(handles=new_handles, labels=labels)
plt.show()