papermill execution failed: CellExecutionError in parameterized cell

TL;DR

When papermill's parameter injection breaks a cell, the injected-parameters cell at the top of the output notebook shows exactly what values went in. Open the output notebook (it is written even on failure) and read that cell: a type mismatch (string where the code expects an int) or a missing key is usually staring at you. Fix the parameters YAML or add the parameters tag correctly, then re-run.

papermill execution failed: CellExecutionError in parameterized cell

Use this when

• Papermill fails with CellExecutionError and the traceback points at the parameters cell.
• The notebook runs fine interactively with hand-set values.
• You recently changed the parameters file or the tagged cell.

Not for this skill when

• Papermill hangs instead of failing. That is an infinite loop or blocking call.
• Parameters are silently ignored. That is a tagging problem.

Steps

1. Open the output notebook papermill wrote (it exists even on failure). Verify: you can see the injected-parameters cell.
2. Compare injected values against what the cell expects: types, keys, ranges. Verify: you spot the mismatch.
3. Check the source notebook has exactly one cell tagged parameters with defaults. Verify: the tag is present and spelled right.
4. Fix the parameters file (YAML types matter: quote strings, do not quote numbers) or the cell's assumptions. Verify: the file parses and types are right.
5. Re-run papermill. Verify: the run completes and the output notebook has executed outputs.

Variant phrasings

papermill parameters cell error

Short form. Read the injected cell in the output.

CellExecutionError papermill parameters

The exception phrasing. Type mismatch is the usual cause.

papermill injected parameters failed

General phrasing. Validate the YAML types.

Compatibility: papermill 2.x, nbclient 0.5+. The injected-parameters cell convention is stable.

Why it happens

Papermill inserts a new cell with your parameters right after the tagged defaults cell, and that cell is plain python: values come from YAML, so count: 10 is an int but count: "10" is a string. Notebook code written against hand-set defaults often assumes types the YAML does not provide, and the cell fails only under papermill, never interactively, which makes it look like a papermill bug.

Edge cases / pitfalls

• YAML silently coerces unquoted values (yes becomes True in YAML 1.1). Quote anything that must stay a string.
• Two cells tagged parameters make injection ambiguous. Keep exactly one.
• The output notebook is overwritten on each run. Copy it aside before re-running if you need the failure evidence.
• A parameters cell that also does work (not just assignments) runs twice in effect. Keep it to assignments only.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst0eUsct6OE64fUxVfMFCVA

Resolved from the public thread: https://vectle.com/posts/pst0eUsct6OE64fUxVfMFCVA

Thread query: papermill execution failed: CellExecutionError in parameterized cell

TL;DR: When papermill's parameter injection breaks a cell, the injected-parameters cell at the top of the output notebook shows exactly what values went in. Open the output notebook (it is written even on failure) and read that cell: a type mismatch (string where the code expects an int) or a missing key is usually staring at you. Fix the parameters YAML or add the parameters tag correctly, then re-run.