How to change the legend fontname in Matplotlib?

To change the legend fontname in Matplotlib, you can use several approaches. The most common methods are using the fontname parameter in legend() or setting font properties for individual legend text elements.

Method 1: Using fontname Parameter

The simplest way is to specify the fontname parameter directly in the legend() method ?

import numpy as np
import matplotlib.pyplot as plt

# Set figure size
plt.rcParams["figure.figsize"] = [7.50, 3.50]
plt.rcParams["figure.autolayout"] = True

# Create data points
x = np.linspace(-5, 5, 100)

# Plot functions
plt.plot(x, np.sin(x), label="y=sin(x)")
plt.plot(x, np.cos(x), label="y=cos(x)")

# Add legend with custom font
plt.legend(loc='upper right', fontname='Arial')

plt.show()

Method 2: Using Font Properties

For more control over font properties, use FontProperties ?

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.font_manager import FontProperties

# Set figure size
plt.rcParams["figure.figsize"] = [7.50, 3.50]
plt.rcParams["figure.autolayout"] = True

# Create data points
x = np.linspace(-5, 5, 100)

# Plot functions
plt.plot(x, np.sin(x), label="y=sin(x)")
plt.plot(x, np.cos(x), label="y=cos(x)")

# Create font properties
font_prop = FontProperties(family='serif', style='italic', size=12)

# Add legend with font properties
plt.legend(loc='upper right', prop=font_prop)

plt.show()

Method 3: Modifying Existing Legend Text

You can also change the font of an existing legend by iterating through its text elements ?

import numpy as np
import matplotlib.pyplot as plt

# Set figure size
plt.rcParams["figure.figsize"] = [7.50, 3.50]
plt.rcParams["figure.autolayout"] = True

# Create data points
x = np.linspace(-5, 5, 100)

# Plot functions
plt.plot(x, np.sin(x), label="y=sin(x)")
plt.plot(x, np.cos(x), label="y=cos(x)")

# Create legend
legend = plt.legend(loc='upper right')

# Change font for each text element
for text in legend.get_texts():
    text.set_fontname('Times New Roman')
    text.set_fontsize(12)

plt.show()

Available Font Options

Common font names you can use include:

• 'Arial', 'Times New Roman', 'Courier New'
• 'serif', 'sans-serif', 'monospace' (generic families)
• 'DejaVu Sans', 'Liberation Sans' (system fonts)

Comparison

Conclusion

Use the fontname parameter for simple font changes, FontProperties for detailed control, or modify existing legend text for post-creation adjustments. The FontProperties approach offers the most flexibility for customizing legend appearance.