N8n Code Python

Python Code Node (native)

Since n8n 2.0 the Code node's Python runs as native Python in a task runner (language: "pythonNative"). The old Pyodide "Python (Beta)" is gone, and with it every n8n helper it had: _input, _json, _node, _now, _today and _jmespath all raise NameError now. Code copied from old templates, forum posts or older docs usually breaks on this.

JavaScript first — stronger than before

Native Python gives you two variables and plain Python, and by default no imports: no json, datetime or re. Everything n8n-specific ($('Node'), $jmespath, Luxon, this.helpers.httpRequest, static data) exists only in JavaScript. Use Python only when the user explicitly asks for it. Even then, first check whether an expression, Edit Fields, or a native node (Crypto, Date & Time, HTML, XML) does the job. See n8n-code-javascript and the transform gatekeeper in n8n-expression-syntax.

Quick start

pythonCopy code
# Run Once for All Items (default mode)
return [
    {"json": {"name": it["json"]["name"], "revenue": it["json"]["revenue"]}}
    for it in _items
    if it["json"].get("active")
]

pythonCopy code
# Run Once for Each Item
row = _item["json"]
return {"json": {**row, "name_upper": (row.get("name") or "").upper()}}

Node config: {"language": "pythonNative", "mode": "runOnceForAllItems" | "runOnceForEachItem", "pythonCode": "..."} on n8n-nodes-base.code typeVersion 2.

The only inputs: _items and _item

• Each variable exists only in its own mode. _items in each-item mode (or _item in all-items mode) raises NameError.
• Dict access only. it["json"]["name"] or it["json"].get("name"). it.json.name raises AttributeError: 'dict' object has no attribute 'json'.
• No other nodes. There is no _node / $('Node') equivalent. If you need data from another branch, bring it in with Merge first, or read it in JavaScript.
• Webhook payloads are under ["body"]: _items[0]["json"].get("body", {}).get("email").
• Binary data isn't covered here. Read and write binary in JavaScript (see n8n-binary-and-data).
• pairedItem: returning _items / _item keeps it. When you build new dicts and downstream uses $('Node').item, add "pairedItem": {"item": i} to each returned item. That isn't verified on native Python yet, so test-run before relying on it.
• Missing keys: prefer .get(key, default). row["missing"] raises KeyError.

Migration table for legacy code:

Imports: blocked by default

Every import (standard library and third-party) is checked against an allowlist before the code runs. The default allowlist is empty, so even import json rejects the whole node:

Copy code
Security violations detected
Line 1: Import of standard library module 'json' is disallowed. Allowed stdlib modules: none

• n8n Cloud: no imports at all.
• Self-hosted: the admin can allowlist modules in the task-runner config (see n8n-self-hosting → TASK_RUNNERS.md). Some instances therefore allow json, datetime and re, and most don't.
• Default to import-free code. If an import would really help, confirm it first: a one-line test node import json + return [{"json": {"ok": True}}], or ask the user. Never assume.
• Without imports: parse JSON strings upstream ({{ JSON.parse($json.payload) }} in Edit Fields). Do date math in expressions (Luxon) or JS. ISO-8601 strings still compare and sort correctly as plain strings. Use the Crypto node for hashing.
• requests, pandas and numpy are never available unless the admin built a custom runner image. Use the HTTP Request node for HTTP.

Sandbox limits (these fail even without imports)

Everything else in plain Python works (verified): comprehensions, generators, lambdas, closures, recursion, try/except, f-strings / .format() / %, sorted/min/max/sum/any/all/ enumerate/zip/round, sets, isinstance, print() (output goes to the browser console).

Return shapes (verified)

Observed on n8n 2.38.5. The auto-wrapping and passthrough behaviours below are undocumented and could change in a later release. Re-check with a test run after upgrading n8n.

Run Once for All Items

Run Once for Each Item

Value conversion on output: tuple becomes a list, set becomes the string "{1, 2}", and a datetime becomes str(dt) ("2026-09-16 10:18:00.025792", not ISO). Convert explicitly (sorted(s), dt.isoformat()).

Prefer the explicit [{"json": ...}] in all-items mode and {"json": ...} in each-item mode. The auto-wrapping works, but the explicit shape makes the intent obvious to the next reader.

Errors and onError

A plain raise ValueError("bad row") fails the node with that message. When the node has an onError continue mode, the three failure kinds behave differently (verified):

The last two are silent-data traps: downstream nodes receive unprocessed input as if the code had run, and the execution still shows success. No error branch catches them. Prevent them (no imports unless confirmed, correct return shape) and confirm with a real test run, checking the Code node's status and output (see n8n-error-handling).

Other messages:

• Python runner unavailable: Python 3 is missing from this system: the self-hosted instance has no Python task runner (the stock image ships none). It's an infrastructure problem, not a code problem. See n8n-self-hosting → TASK_RUNNERS.md.
• validate_node / validate_workflow catch a few Python mistakes (import requests, missing return, return None). They do not catch _input/_json, dot access, blocked stdlib imports, dunder access or classes. A test execution is the only reliable check.

Performance

Each Python Code node costs roughly 0.4 s (about 1 s when the runner is cold), noticeably more than a JS Code node or an expression. Process lists in Run Once for All Items mode rather than per item, and don't chain several small Python nodes where one would do.

Checklist

• The user actually asked for Python. Otherwise JS, an expression, or a native node.
• Mode matches the variable: _items (all items) / _item (each item).
• Only dict access. No _input, _json, _node, _now or _jmespath.
• No import unless confirmed allowlisted on this instance.
• No classes, type(), getattr/hasattr or dunders. nonlocal instead of global.
• Return shape fits the mode. Sets and datetimes converted explicitly.
• Ran a real test execution and inspected the output items (validation alone won't catch the traps above).

Reference

• COMMON_PATTERNS.md: 12 import-free patterns, each verified on a live n8n instance (filter, aggregate, group, dedupe, top N, flatten, validate, drop items, text report, safe nested access, running totals, ISO timestamps).

Related skills

• n8n-code-javascript: the default for Code nodes, with all n8n helpers.
• n8n-expression-syntax: $jmespath, Luxon and the transform gatekeeper, often a better fit than any Code node.
• n8n-code-tool: Python in the AI-agent Custom Code Tool (_query, returns a string).
• n8n-error-handling: wiring error outputs; the passthrough trap above.
• n8n-self-hosting: enabling the Python task runner and allowlisting modules.