Python Bokeh output_file: Save Plots as HTML Files

The output_file() function in Bokeh is a crucial tool that allows you to save your interactive visualizations as standalone HTML files. This makes sharing and distributing your plots incredibly convenient.

Understanding output_file() Function

Before creating visualizations with Bokeh, it's essential to properly set up Bokeh in your Python environment. The output_file() function is typically the first step in the plotting process.

Basic Syntax and Parameters

The basic syntax of output_file() includes several parameters that control how your plot is saved:

from bokeh.plotting import figure, output_file, show

# Basic syntax
output_file(filename, title=None, mode="cdn", root_dir=None)

# Example
output_file("my_plot.html", title="My First Bokeh Plot")

Creating a Simple Plot Example

Let's create a basic line plot to demonstrate how output_file() works in practice:

from bokeh.plotting import figure, output_file, show
import numpy as np

# Set the output file
output_file("line_plot.html", title="Simple Line Plot")

# Create sample data
x = np.linspace(0, 10, 50)
y = np.sin(x)

# Create the plot
p = figure(title="Sine Wave", x_axis_label='x', y_axis_label='y')
p.line(x, y, line_color="blue", line_width=2)

# Show the plot
show(p)

Advanced Usage and Customization

When working with Bokeh's interactive plots, you can customize how your HTML files are generated and stored.

Setting Custom Directory Path

import os
from bokeh.plotting import figure, output_file, show

# Set custom directory
output_dir = "my_plots"
if not os.path.exists(output_dir):
    os.makedirs(output_dir)

# Save plot in custom directory
output_file(os.path.join(output_dir, "custom_plot.html"))

# Create a simple plot
p = figure(title="Plot in Custom Directory")
p.circle([1, 2, 3], [4, 5, 6])

show(p)

Multiple Plots in One File

You can combine multiple plots into a single HTML file using layouts:

from bokeh.layouts import column
from bokeh.plotting import figure, output_file, show

# Set output file for multiple plots
output_file("multiple_plots.html")

# Create first plot
p1 = figure(title="Plot 1")
p1.circle([1, 2, 3], [4, 5, 6])

# Create second plot
p2 = figure(title="Plot 2")
p2.line([1, 2, 3], [2, 4, 6])

# Combine plots and show
show(column(p1, p2))

Best Practices and Tips

File naming conventions are important when working with output_file(). Use descriptive names and always include the .html extension.

Consider these important tips:

• Always verify file permissions before saving
• Use absolute paths when working in different directories
• Include meaningful titles for better organization

Common Issues and Solutions

If you encounter issues with displaying your plots in the browser, ensure you're calling show() after creating your visualization.

# Common mistake - forgot to call show()
output_file("forgotten_plot.html")
p = figure()
p.line([1, 2, 3], [1, 2, 3])
# Plot won't appear without show()
show(p)  # Always include this!

Conclusion

The output_file() function is a fundamental tool in Bokeh that enables you to create standalone HTML visualizations. Understanding its proper usage is crucial for effective data visualization sharing.

Remember to always specify your output file before creating your plot, use meaningful file names, and properly organize your visualization files for better maintainability.