Preprocessors

Preprocessors in LabPaper modify notebook content before the conversion process begins. They handle tasks like code execution, markdown processing, and content validation.

Available Preprocessors

PygmentizePreprocessor

Handles syntax highlighting for code blocks in the LaTeX output. This preprocessor generates the necessary Pygments definitions and styles for proper code formatting in the final PDF.

Configuration options:

style (str, default: “abap”): Name of the pygments style to use for syntax highlighting

Example configuration:

c.PygmentizePreprocessor.style = "monokai"

PythonMarkdownPreprocessor

A powerful preprocessor that enables dynamic content generation in markdown cells and manages document metadata. It provides two main features:

Dynamic Markdown Content:

Evaluates Python expressions embedded in markdown cells using {{ expression }} syntax
Executes code cells to build up a namespace for expression evaluation
Provides access to matplotlib (plt) in the evaluation namespace

Example usage in markdown cells:

The mean of our data is {{ data.mean() }}
The plot shows {{ len(figures) }} different conditions

Note: The preprocessor automatically closes matplotlib figures after execution to prevent display issues.

Configuration

Preprocessors can be configured in your Jupyter configuration:

c.LabPaperExporter.preprocessors = [
    'labpaper.preprocessors.PygmentizePreprocessor',
    'labpaper.preprocessors.PythonMarkdownPreprocessor'
]

Custom Preprocessors

Create custom preprocessors by inheriting from nbconvert.preprocessors.Preprocessor:

from nbconvert.preprocessors import Preprocessor

class CustomPreprocessor(Preprocessor):
    def preprocess_cell(self, cell, resources, index):
        # Your preprocessing logic here
        return cell, resources

Execution Order

PythonMarkdownPreprocessor runs first to:
- Set document metadata
- Execute code cells to build namespace
- Process markdown cells with embedded expressions
PygmentizePreprocessor runs next to:
- Generate syntax highlighting definitions
- Apply code styling for the LaTeX output