pandoc filters – Hamel’s Blog - Hamel Husain

Two python packages

The tutorial on pandoc filters can help you get oriented to the general idea. If rolling your own filters, you probably want to use the JSON filters. Furthermore you can understand the pandoc AST by using the -t native flag (examples of this are shown later).

The minimal notebook

Here is minimal notebook we are working with:

json title="minimal.ipynb" { "cells": [ { "cell_type": "markdown", "metadata": {}, "source": [ "## A minimal notebook" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "<MyTag></MyTag>" ] }, { "cell_type": "code", "execution_count": 1, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "2\n" ] } ], "source": [ "# Do some arithmetic\n", "print(1+1)" ] } ], "metadata": { "interpreter": { "hash": "42fd40e048e0585f88ec242f050f7ef0895cf845a8dd1159352394e5826cd102" }, "kernelspec": { "display_name": "Python 3.9.7 ('base')", "language": "python", "name": "python3" }, "language_info": { "codemirror_mode": { "name": "ipython", "version": 3 }, "file_extension": ".py", "mimetype": "text/x-python", "name": "python", "nbconvert_exporter": "python", "pygments_lexer": "ipython3", "version": "3.9.7" } }, "nbformat": 4, "nbformat_minor": 4 }

Minimal ipynb to md converstion with pandoc

$ pandoc --to gfm minimal.ipynb <div class="cell markdown"> ## A minimal notebook </div> <div class="cell markdown"> <MyTag></MyTag> </div> <div class="cell code" execution_count="1"> ``` python # Do some arithmetic print(1+1) ``` <div class="output stream stdout"> 2 </div> </div>

Minimal ipynb to md converstion with quarto

$ quarto render minimal.ipynb --to gfm pandoc to: gfm+footnotes+tex_math_dollars-yaml_metadata_block output-file: minimal.md standalone: true default-image-extension: png filters: - crossref Output created: minimal.md

This creates

## A minimal notebook <MyTag></MyTag> ``` python # Do some arithmetic print(1+1) ``` 2

Running Pandoc With those Extensions

running pandoc with --standalone --to gfm+footnotes+tex_math_dollars-yaml_metadata_block still adds the divs and looks different than quarto. Somewhere, maybe quarto is removing the divs. We can see the Div elements in the AST when we explore panflute in the sections below.

How to use panflute

The examples are helpful.

This filter places CodeOutput blocks around code as well as changes the codefence to have file=script.py in order to hack the code fence.

#!/Users/hamel/opt/anaconda3/bin/python #flute.py from typing import Text from panflute import * from logging import warning def increase_header_level(elem, doc): if type(elem) == CodeBlock and type(elem.parent.prev) == CodeBlock: return ([RawBlock("<CodeOutput>"), elem, RawBlock("</CodeOutput>")]) elif type(elem) == CodeBlock: elem.classes = ['file=script.py'] def main(doc=None): return run_filter(increase_header_level, doc=doc) if __name__ == "__main__": main()

This is how we can use this filter and see the rendered output:

$ pandoc --to gfm minimal.ipynb --filter "flute.py" <div class="cell markdown"> ## A minimal notebook </div> <div class="cell markdown"> <MyTag></MyTag> </div> <div class="cell code" execution_count="1"> ``` file=script.py # Do some arithmetic print(1+1) ``` <div class="output stream stdout"> <CodeOutput> 2 </CodeOutput> </div> </div>

Note: we could probably replace the inner div with the output class with <CodeOutput> tag

Just for completeness, this is the schema of the minimal notebook using the --to native flag prior to applying the filter:

$pandoc --to native minimal.ipynb [ Div ( "" , [ "cell" , "markdown" ] , [] ) [ Header 2 ( "a-minimal-notebook" , [] , [] ) [ Str "A" , Space , Str "minimal" , Space , Str "notebook" ] ] , Div ( "" , [ "cell" , "markdown" ] , [] ) [ Para [ RawInline (Format "html") "<MyTag>" , RawInline (Format "html") "</MyTag>" ] ] , Div ( "" , [ "cell" , "code" ] , [ ( "execution_count" , "1" ) ] ) [ CodeBlock ( "" , [ "python" ] , [] ) "# Do some arithmetic\nprint(1+1)" , Div ( "" , [ "output" , "stream" , "stdout" ] , [] ) [ CodeBlock ( "" , [] , [] ) "2\n" ] ] ]

And after applying the filter:

$pandoc --to native minimal.ipynb --filter flute.py [ Div ( "" , [ "cell" , "markdown" ] , [] ) [ Header 2 ( "a-minimal-notebook" , [] , [] ) [ Str "A" , Space , Str "minimal" , Space , Str "notebook" ] ] , Div ( "" , [ "cell" , "markdown" ] , [] ) [ Para [ RawInline (Format "html") "<MyTag>" , RawInline (Format "html") "</MyTag>" ] ] , Div ( "" , [ "cell" , "code" ] , [ ( "execution_count" , "1" ) ] ) [ CodeBlock ( "" , [ "file=script.py" ] , [] ) "# Do some arithmetic\nprint(1+1)" , Div ( "" , [ "output" , "stream" , "stdout" ] , [] ) [ RawBlock (Format "html") "<CodeOutput>" , CodeBlock ( "" , [] , [] ) "2\n" , RawBlock (Format "html") "</CodeOutput>" ] ] ]