How do I change the font size of ticks of matplotlib.pyplot.colorbar.ColorbarBase?

To change the font size of ticks in a matplotlib colorbar, you can use the tick_params() method on the colorbar's axis. This allows you to customize the appearance of tick labels including their size.

Basic Example

Here's how to create a colorbar and modify its tick font size ?

import numpy as np
import matplotlib.pyplot as plt

# Set figure properties
plt.rcParams["figure.figsize"] = [7.00, 3.50]
plt.rcParams["figure.autolayout"] = True

# Create random 5x5 data
data = np.random.rand(5, 5)

# Display data as image with colormap
im = plt.imshow(data, interpolation="nearest", cmap="copper")

# Create colorbar
cbar = plt.colorbar(im)

# Set tick font size
tick_font_size = 10
cbar.ax.tick_params(labelsize=tick_font_size)

plt.show()

Multiple Font Size Examples

You can experiment with different font sizes to find what works best for your visualization ?

import numpy as np
import matplotlib.pyplot as plt

# Create sample data
data = np.random.rand(8, 8)

# Create subplots for comparison
fig, axes = plt.subplots(1, 3, figsize=(12, 4))

font_sizes = [8, 12, 16]
titles = ['Small (8pt)', 'Medium (12pt)', 'Large (16pt)']

for i, (ax, font_size, title) in enumerate(zip(axes, font_sizes, titles)):
    # Plot image
    im = ax.imshow(data, cmap='viridis')
    
    # Add colorbar with specified font size
    cbar = plt.colorbar(im, ax=ax)
    cbar.ax.tick_params(labelsize=font_size)
    
    # Set subplot title
    ax.set_title(title)

plt.tight_layout()
plt.show()

Advanced Customization

You can also customize other aspects of the colorbar ticks ?

import numpy as np
import matplotlib.pyplot as plt

# Generate data
data = np.random.rand(6, 6)

# Create plot
fig, ax = plt.subplots(figsize=(8, 6))
im = ax.imshow(data, cmap='plasma')

# Create colorbar with advanced customization
cbar = plt.colorbar(im, ax=ax)

# Customize tick parameters
cbar.ax.tick_params(
    labelsize=14,        # Font size
    colors='red',        # Text color
    width=2,             # Tick width
    length=6             # Tick length
)

# Set colorbar label
cbar.set_label('Values', fontsize=16, color='blue')

plt.title('Customized Colorbar Ticks', fontsize=18)
plt.show()

Key Parameters

Conclusion

Use cbar.ax.tick_params(labelsize=size) to change colorbar tick font size. You can also customize colors, width, and length for better visualization. The tick_params() method provides complete control over colorbar tick appearance.