increase the linewidth of the legend lines in matplotlib

Solution 1:

Here's a simple example of how to do it:

import numpy as np
import matplotlib.pyplot as plt

# make some data
x = np.linspace(0, 2*np.pi)
y1 = np.sin(x)
y2 = np.cos(x)

# plot sin(x) and cos(x)
p1 = plt.plot(x, y1, 'b-', linewidth=1.0)
p2 = plt.plot(x, y2, 'r-', linewidth=1.0)

# make a legend for both plots
leg = plt.legend([p1, p2], ['sin(x)', 'cos(x)'], loc=1)

# set the linewidth of each legend object
for legobj in leg.legendHandles:
    legobj.set_linewidth(2.0)

plt.show()

Solution 2:

@Brendan Wood's method use the api provided by pyplot. In matplotlib, the object oriented style using axes is prefered. The following is how you can achieve this using axes method.

import numpy as np
import matplotlib.pyplot as plt

# make some data
x = np.linspace(0, 2*np.pi)
y1 = np.sin(x)
y2 = np.cos(x)

fig, ax = plt.subplots()
ax.plot(x, y1, linewidth=1.0, label='sin(x)')
ax.plot(x, y2, linewidth=1.0, label='cos(x)')
leg = ax.legend()

for line in leg.get_lines():
    line.set_linewidth(4.0)

plt.show()

The produced plot is shown below,