Runs parameterized Jupyter notebooks as reproducible batch report generators with papermill, renders them to HTML/PDF with nbconvert, aggregates results across samples, and makes notebook outputs trustworthy. Use when generating per-sample analysis reports, executing a notebook template across many datasets, or fixing notebooks that do not reproduce.
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Runs parameterized Jupyter notebooks as reproducible batch report generators with papermill, renders them to HTML/PDF with nbconvert, aggregates results across samples, and makes notebook outputs trustworthy. Use when generating per-sample analysis reports, executing a notebook template across many datasets, or fixing notebooks that do not reproduce.
Before using code patterns, verify installed versions match. If versions differ:
Python: pip show papermill then help(papermill.execute_notebook)
CLI: papermill --help, jupyter nbconvert --help
If code throws ImportError, AttributeError, or TypeError, introspect the installed package and adapt the example to match the actual API rather than retrying.
Jupyter Reports with Papermill
"Generate a reproducible analysis report" -> Execute a parameterized notebook in a clean kernel, producing an executed-notebook artifact, then render it to a code-hidden HTML/PDF report.
CLI: jupyter nbconvert --execute --to html notebook.ipynb
The Load-Bearing Idea: A Notebook Has Hidden State; the Report Is the Executed Artifact
A .ipynb is JSON holding cell source, saved outputs, and per-cell execution_count integers - and those three are decoupled. The kernel is a long-lived process with a mutable namespace, so a user can run cell 5, edit cell 2, rerun it, delete cell 3, run cell 7, and save. The stored outputs then reflect a kernel state that NO top-to-bottom rerun reproduces. Non-monotonic execution counts are the forensic tell.
This is intrinsic to the REPL-on-a-document model, not a bug. The discipline answer is mechanical: Restart Kernel and Run All before sharing, so saved outputs equal one clean linear run. papermill and nbconvert --execute are that discipline automated - they always spin up a FRESH kernel and run cells strictly in document order, so the output is by construction the record of one clean run. The value is not "trust the saved outputs," it is "regenerate them from a known-empty state."
The empirical case (Pimentel et al.): of ~1.4M GitHub notebooks, only ~24% of those executed finished without error and only ~4% reproduced their stored outputs; ~36% had out-of-order cells, and the dominant failure was ImportError - environment, not logic. (It is a public-GitHub corpus, so the absolute rates carry selection bias, but the failure mode is the lesson.) Two lessons: saved outputs are not reproducible (always re-execute), and the #1 fix is pinning the environment (see below).
Two Artifacts People Conflate
Executed notebook - papermill's output, or nbconvert --execute --to notebook. A record of the run: same cells, freshly computed outputs, an injected-parameters cell. For audit/debug/aggregation, not for humans to read as prose.
Human report - nbconvert --to html/pdf, optionally --no-input to hide code. The rendered deliverable.
A papermill pipeline does both: execute the parameterized notebook -> output .ipynb (the evidence) -> convert to HTML/PDF (the report).
Parameterizing with papermill
Tag ONE cell parameters holding defaults. At execution papermill inserts a NEW cell tagged injected-parameters immediately AFTER it, containing only the overrides; because Python runs top-to-bottom, the injected cell shadows the defaults.
import papermill as pm
pm.execute_notebook('template.ipynb', 'out/sampleA.ipynb',
parameters={'sample_id': 'sampleA', 'fdr_threshold': 0.05})
If NO cell is tagged parameters, the injected cell goes at the TOP and downstream references to a param raise NameError. Keep all parameters in one tagged cell.
Type coercion is the #1 CLI gotcha.-p name value YAML-parses the value (-p n 5 -> int, -p flag true -> bool); -r name value keeps it a raw string (-r chrom 1 -> "1", needed for sample IDs like 007 or chromosome "1"). -y/--parameters_yaml and -f/--parameters_file pass lists/dicts. The Python API passes native objects directly with no YAML round-trip - prefer it in pipelines to avoid coercion surprises.
Execution Controls That Matter in Pipelines
execution_timeout (CLI --execution-timeout) - seconds per cell; default is forever (None). A long bioinformatics cell hangs a pipeline silently without this. Set it.
kernel_name / --kernel - must be a REGISTERED kernelspec; a mismatch is a top failure cause. The kernel must point at the pinned environment.
log_output=True / --log-output - stream each cell's stdout/stderr for CI visibility.
On a cell exception papermill raises PapermillExecutionError, STILL writes the output notebook with the traceback captured (evidence preserved), then exits non-zero. Tag a cell raises-exception to allow it to fail without aborting. Fail loud, keep the artifact.
papermill reads/writes notebooks from s3://, gs://, adl:///abs://, and http(s):// out of the box (cloud connectors are extras: pip install papermill[s3]), so serverless per-sample execution works.
The fresh-kernel guarantee holds when papermill owns the kernel lifecycle (the default execute_notebook path). Advanced patterns that reuse a kernel across notebooks forgo the from-empty-state guarantee - let papermill create the kernel.
Rendering to a Report
nbconvert --execute runs the notebook top-to-bottom in a fresh kernel and writes regenerated outputs - that re-execution, not the saved outputs, is what makes a converted report reproducible.
jupyter nbconvert --to html --no-input out/sampleA.ipynb # code-hidden stakeholder report
jupyter nbconvert --execute --to html template.ipynb # execute then render in one step
jupyter nbconvert --to webpdf out/sampleA.ipynb # PDF without LaTeX
--to pdf needs a LaTeX toolchain (xelatex + pandoc) - the classic CI pain. --to webpdf renders HTML then prints via headless Chromium (pip install nbconvert[webpdf], --allow-chromium-download) and avoids TeX entirely. The tradeoff: webpdf uses Chromium page geometry, so wide tables and long code lines can clip at the page edge, whereas LaTeX --to pdf paginates and wraps better for table-heavy reports.
--no-input hides all code; --no-prompt drops the In[ ]:/Out[ ]: prompts; TagRemovePreprocessor.remove_cell_tags strips cells by tag (tag setup cells to remove them). Custom branded layouts use the nbconvert 6+ directory-template system (--template <name>).
Aggregating Results Across Samples
papermill.record is deprecated (since papermill 1.0). Use scrapbook: in the template, import scrapbook as sb; sb.glue('auc', 0.91) records named scraps (and sb.glue('fig', obj, display=True) for figures). Downstream, sb.read_notebooks('reports/').papermill_dataframe aggregates every executed notebook's scraps into one tidy table - the canonical pattern for looping papermill over a sample sheet then collecting per-sample QC into a cohort summary.
Version Control: Never Commit Outputs
.ipynb is JSON with embedded base64 outputs and execution_count, so committing it raw gives giant unreviewable diffs, brutal merge conflicts, and leaked data. Three complementary fixes:
nbstripout - a git clean filter (*.ipynb filter=nbstripout in .gitattributes) that strips outputs and execution counts on git add; the working copy keeps its outputs. Highest-leverage single fix.
jupytext - pairs .ipynb with a text twin (py:percent is runnable and diff-friendly, or Markdown/.qmd); commit the text file as source of truth, regenerate outputs. Lets a notebook be code-reviewed as a normal PR.
jupyter-cache - caches executed outputs keyed by a code-cell hash; the engine Jupyter Book/MyST-NB and Quarto use to skip re-running expensive cells. Right tool when notebooks are doc sources with long compute.
Reproducible Execution Is Not Reproducible Science
State this plainly: papermill and nbconvert --execute guarantee EXECUTION ORDER and a clean kernel - they do NOT guarantee the ENVIRONMENT or numerical determinism. The same parameterized notebook rerun against newer numpy/scanpy, a different BLAS, or an unseeded RNG runs flawlessly and produces DIFFERENT numbers. Order-reproducibility is necessary, not sufficient. Pair papermill with: a pinned environment (conda lockfile / requirements.txt with exact versions, ideally a container; the registered kernel must point at it), seeded RNGs for any stochastic step (clustering, UMAP, splits, bootstraps), and pinned reference/DB versions. To catch silent drift, nbval (pytest --nbval) re-executes and compares new outputs against stored ones in CI.
When a Notebook Report Is the Wrong Tool
The notebook is the REPORT, not the PIPELINE. Heavy compute (alignment, variant calling, large scanpy integration, anything multi-hour or needing a scheduler, retries, or parallel fan-out) belongs in a workflow manager (Snakemake/Nextflow/WDL). papermill notebooks shine as the final per-sample or per-cohort summary plus figures over already-computed results. Rule of thumb: if --retry, --cluster, or a DAG is wanted, it is a pipeline; if a parameterized HTML/PDF of results is wanted, it is a papermill report. Note Quarto can consume a .ipynb directly, so papermill (parameterize/execute) and Quarto (render) interoperate.
Common Errors
Symptom
Cause
Fix
Saved outputs do not match a rerun
Out-of-order interactive execution / hidden state
Restart-and-run-all; let papermill/nbconvert --execute regenerate
Parameter is a bool when a string was wanted
-p YAML-parses values
use -r name value for raw strings, or the Python API
NameError on a parameter
No parameters-tagged cell
tag one cell parameters; keep all params there
Pipeline hangs on one cell
execution_timeout defaults to forever
set execution_timeout
--to pdf fails in CI
no LaTeX toolchain
use --to webpdf (headless Chromium)
Giant notebook diffs / leaked data in git
committing outputs
nbstripout filter or jupytext pairing
Reruns months later give different numbers
environment/seed not pinned
pin env + container, seed RNGs, nbval in CI
Related Skills
reporting/quarto-reports - Document-first reporting that can render the same notebooks
Pimentel JF, Murta L, Braganholo V, Freire J. A large-scale study about quality and reproducibility of Jupyter notebooks. MSR '19, IEEE/ACM. 2019:507-517. doi:10.1109/MSR.2019.00077
Pimentel JF, Murta L, Braganholo V, Freire J. Understanding and improving the quality and reproducibility of Jupyter notebooks. Empir Softw Eng. 2021;26:65. doi:10.1007/s10664-021-09961-9
Rule A, Birmingham A, Zuniga C, et al. Ten simple rules for writing and sharing computational analyses in Jupyter Notebooks. PLoS Comput Biol. 2019;15(7):e1007007. doi:10.1371/journal.pcbi.1007007
Kluyver T, Ragan-Kelley B, Pérez F, et al. Jupyter Notebooks - a publishing format for reproducible computational workflows. ELPUB 2016, IOS Press. 2016:87-90. doi:10.3233/978-1-61499-649-1-87
