nteract/papermill

Parameter strings cannot contain "="

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#864 opened on Feb 28, 2026

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 (0 comments) (0 reactions) (0 assignees)Python (5,381 stars) (402 forks)batch import
bughelp wanted

Description

🐛 Bug

# %% tags=["parameters"]

s = "a=b"

# %%
print(s)

This fails with: Passed unknown parameter: s`". Seems like papermill naively counts = on the parameter line, so it's treated as unparseable, then flagged as “unknown parameter”.

Papermill version: 2.6.0.

Contributor guide

Tech stack
python
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Basic Python knowledgeFamiliarity with papermill parameter parsing
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
80
Research direction
The issue is that parameter strings containing "=" are incorrectly parsed because papermill naively splits on '='. Look for the parameter parsing logic in the papermill source code, likely in files related to notebook execution or parameter injection (e.g., `papermill/execute.py` or `papermill/iorw.py`). The fix should use a more robust method to parse key value pairs, such as splitting only on the first '=' or using a regex that accounts for escaped '='. Ensure that the fix does not break existing parameter handling. No linked PRs or comments exist yet, so the issue is open for contribution.