Overview
If you are rendering existing Jupyter notebooks that were not created with Quarto in mind, you may wish to do some pre-processing on the notebook prior to its conversion to markdown. This can be accomplished by specifying one or more ipynb-filters. These filters are passed the JSON representation of the notebook on stdin and should write a transformed JSON representation to stdout.






Note



The purpose of notebook filters is to adapt existing .ipynb files for use with Quarto. Consequently, notebook filters are only run when the original input is an .ipynb file (they are not run for .qmd files).




Example
For example, this notebook filter uses the nbformat package to read a notebook, prepend a comment to the source of each code cell, and then write it back to stdout:
import sys
import nbformat

# read notebook from stdin
nb = nbformat.reads(sys.stdin.read(), as_version = 4)

# prepend a comment to the source of each cell
for index, cell in enumerate(nb.cells):
  if cell.cell_type == 'code':
     cell.source = "# comment\n" + cell.source
  
# write notebook to stdout 
nbformat.write(nb, sys.stdout)
You can arrange for this filter to be run using the ipynb-filters option (specified at either the document or project level):
---
ipynb-filters:
  - filter.py
---
Note that the current working directory for the filter will be set to the location of the input notebook.