N8n Code Python

n8n Code Python

Expert guidance for writing Python in n8n Code nodes.

Based on n8n-skills by Romuald Członkowski

Python Code Node Basics

n8n supports Python in Code nodes with some differences from JavaScript.

Run Once for All Items

# Access all input items
items = _input.all()

# Process and return
return [{"json": {**item.json, "processed": True}} for item in items]

Run Once for Each Item

# Access current item
data = _input.item.json

# Return single item
return {"json": {**data, "processed": True}}

Accessing Data

Current Node Input

# All items
items = _input.all()

# First item
first = _input.first()

# Current item (in "each item" mode)
current = _input.item

# JSON data
data = _input.first().json

Execution Context

# Note: Limited compared to JavaScript
# Access via items or hardcoded values

Common Patterns

Transform All Items

items = _input.all()

return [
    {
        "json": {
            "id": item.json["id"],
            "name": item.json["name"].upper(),
            "processed": True
        }
    }
    for item in items
]

Filter Items

items = _input.all()

return [
    {"json": item.json}
    for item in items
    if item.json.get("status") == "active"
]

Aggregate Data

items = _input.all()

total = sum(item.json.get("amount", 0) for item in items)
count = len(items)

return [{
    "json": {
        "total": total,
        "count": count,
        "average": total / count if count > 0 else 0
    }
}]

Group By

from collections import defaultdict

items = _input.all()
grouped = defaultdict(list)

for item in items:
    key = item.json.get("category", "unknown")
    grouped[key].append(item.json)

return [
    {"json": {"category": k, "items": v, "count": len(v)}}
    for k, v in grouped.items()
]

JSON Parsing

import json

items = _input.all()

return [
    {
        "json": {
            "parsed": json.loads(item.json.get("rawData", "{}"))
        }
    }
    for item in items
]

Error Handling

import json

items = _input.all()
results = []

for item in items:
    try:
        parsed = json.loads(item.json.get("rawData", "{}"))
        results.append({"json": {"success": True, "data": parsed}})
    except Exception as e:
        results.append({"json": {"success": False, "error": str(e)}})

return results

Date/Time Handling

from datetime import datetime, timedelta

# Current time
now = datetime.now()

# Parse ISO date
date = datetime.fromisoformat("2024-01-15T10:30:00")

# Format
formatted = now.strftime("%Y-%m-%d %H:%M:%S")

# Add/subtract
next_week = now + timedelta(days=7)
yesterday = now - timedelta(days=1)

# Return with dates
return [{
    "json": {
        "now": now.isoformat(),
        "formatted": formatted,
        "nextWeek": next_week.isoformat()
    }
}]

Working with Pandas

⚠️ Note: pandas may not be available in all n8n installations. Check your environment.

import pandas as pd

items = _input.all()

# Convert to DataFrame
data = [item.json for item in items]
df = pd.DataFrame(data)

# Process with pandas
df["total"] = df["price"] * df["quantity"]
df_grouped = df.groupby("category").agg({"total": "sum"}).reset_index()

# Convert back to n8n format
return [{"json": row} for row in df_grouped.to_dict(orient="records")]

Webhook Data Access

CRITICAL: Webhook data is under .body:

# ❌ Wrong
message = _input.first().json.get("message")

# ✅ Correct - webhook data is in body
body = _input.first().json.get("body", {})
message = body.get("message")
headers = _input.first().json.get("headers", {})
query = _input.first().json.get("query", {})

Available Libraries

Standard Python libraries typically available:

• json - JSON parsing
• datetime - Date/time handling
• re - Regular expressions
• collections - Data structures
• math - Mathematical functions
• base64 - Encoding
• hashlib - Hashing

import json
import re
import hashlib
from datetime import datetime
from collections import defaultdict

# Use hashlib
hash_value = hashlib.sha256(data.encode()).hexdigest()

# Use regex
matches = re.findall(r"\d+", text)

Common Mistakes

1. Wrong Return Format

# ❌ Wrong - must return list of dicts with "json" key
return {"name": "John"}

# ✅ Correct
return [{"json": {"name": "John"}}]

2. Using dot notation for dict access

# ❌ Wrong - Python dicts use brackets
name = item.json.name

# ✅ Correct
name = item.json["name"]
# or safer:
name = item.json.get("name", "default")

3. Not Handling Missing Keys

# ❌ Wrong - KeyError if missing
value = item.json["optional_field"]

# ✅ Correct
value = item.json.get("optional_field", "default")

4. Returning dict instead of list

# ❌ Wrong in "all items" mode
return {"json": {"result": "data"}}

# ✅ Correct - always return list
return [{"json": {"result": "data"}}]

Python vs JavaScript in n8n

Best Practices

1. Always return list of {"json": {...}} dicts
2. Use .get() for safe dict access
3. Handle exceptions with try/except
4. Import at top of code block
5. Test with simple data first
6. Access webhook data via .body

Quick Reference

Based on n8n-skills by Romuald Członkowski • Adapted for Moltbot by fazer.ai

Source: fazer-ai/moltbot-skill-n8n — distributed by TomeVault.