Initial commit

2025-11-29 18:17:17 +08:00
commit 6062d3994e
39 changed files with 21748 additions and 0 deletions
--- a/skills/n8n-code-python/SKILL.md
+++ b/skills/n8n-code-python/SKILL.md
@@ -0,0 +1,748 @@
+---
+name: n8n-code-python
+description: Write Python code in n8n Code nodes. Use when writing Python in n8n, using _input/_json/_node syntax, working with standard library, or need to understand Python limitations in n8n Code nodes.
+---
+
+# Python Code Node (Beta)
+
+Expert guidance for writing Python code in n8n Code nodes.
+
+---
+
+## ⚠️ Important: JavaScript First
+
+**Recommendation**: Use **JavaScript for 95% of use cases**. Only use Python when:
+- You need specific Python standard library functions
+- You're significantly more comfortable with Python syntax
+- You're doing data transformations better suited to Python
+
+**Why JavaScript is preferred:**
+- Full n8n helper functions ($helpers.httpRequest, etc.)
+- Luxon DateTime library for advanced date/time operations
+- No external library limitations
+- Better n8n documentation and community support
+
+---
+
+## Quick Start
+
+```python
+# Basic template for Python Code nodes
+items = _input.all()
+
+# Process data
+processed = []
+for item in items:
+    processed.append({
+        "json": {
+            **item["json"],
+            "processed": True,
+            "timestamp": datetime.now().isoformat()
+        }
+    })
+
+return processed
+```
+
+### Essential Rules
+
+1. **Consider JavaScript first** - Use Python only when necessary
+2. **Access data**: `_input.all()`, `_input.first()`, or `_input.item`
+3. **CRITICAL**: Must return `[{"json": {...}}]` format
+4. **CRITICAL**: Webhook data is under `_json["body"]` (not `_json` directly)
+5. **CRITICAL LIMITATION**: **No external libraries** (no requests, pandas, numpy)
+6. **Standard library only**: json, datetime, re, base64, hashlib, urllib.parse, math, random, statistics
+
+---
+
+## Mode Selection Guide
+
+Same as JavaScript - choose based on your use case:
+
+### Run Once for All Items (Recommended - Default)
+
+**Use this mode for:** 95% of use cases
+
+- **How it works**: Code executes **once** regardless of input count
+- **Data access**: `_input.all()` or `_items` array (Native mode)
+- **Best for**: Aggregation, filtering, batch processing, transformations
+- **Performance**: Faster for multiple items (single execution)
+
+```python
+# Example: Calculate total from all items
+all_items = _input.all()
+total = sum(item["json"].get("amount", 0) for item in all_items)
+
+return [{
+    "json": {
+        "total": total,
+        "count": len(all_items),
+        "average": total / len(all_items) if all_items else 0
+    }
+}]
+```
+
+### Run Once for Each Item
+
+**Use this mode for:** Specialized cases only
+
+- **How it works**: Code executes **separately** for each input item
+- **Data access**: `_input.item` or `_item` (Native mode)
+- **Best for**: Item-specific logic, independent operations, per-item validation
+- **Performance**: Slower for large datasets (multiple executions)
+
+```python
+# Example: Add processing timestamp to each item
+item = _input.item
+
+return [{
+    "json": {
+        **item["json"],
+        "processed": True,
+        "processed_at": datetime.now().isoformat()
+    }
+}]
+```
+
+---
+
+## Python Modes: Beta vs Native
+
+n8n offers two Python execution modes:
+
+### Python (Beta) - Recommended
+- **Use**: `_input`, `_json`, `_node` helper syntax
+- **Best for**: Most Python use cases
+- **Helpers available**: `_now`, `_today`, `_jmespath()`
+- **Import**: `from datetime import datetime`
+
+```python
+# Python (Beta) example
+items = _input.all()
+now = _now  # Built-in datetime object
+
+return [{
+    "json": {
+        "count": len(items),
+        "timestamp": now.isoformat()
+    }
+}]
+```
+
+### Python (Native) (Beta)
+- **Use**: `_items`, `_item` variables only
+- **No helpers**: No `_input`, `_now`, etc.
+- **More limited**: Standard Python only
+- **Use when**: Need pure Python without n8n helpers
+
+```python
+# Python (Native) example
+processed = []
+
+for item in _items:
+    processed.append({
+        "json": {
+            "id": item["json"].get("id"),
+            "processed": True
+        }
+    })
+
+return processed
+```
+
+**Recommendation**: Use **Python (Beta)** for better n8n integration.
+
+---
+
+## Data Access Patterns
+
+### Pattern 1: _input.all() - Most Common
+
+**Use when**: Processing arrays, batch operations, aggregations
+
+```python
+# Get all items from previous node
+all_items = _input.all()
+
+# Filter, transform as needed
+valid = [item for item in all_items if item["json"].get("status") == "active"]
+
+processed = []
+for item in valid:
+    processed.append({
+        "json": {
+            "id": item["json"]["id"],
+            "name": item["json"]["name"]
+        }
+    })
+
+return processed
+```
+
+### Pattern 2: _input.first() - Very Common
+
+**Use when**: Working with single objects, API responses
+
+```python
+# Get first item only
+first_item = _input.first()
+data = first_item["json"]
+
+return [{
+    "json": {
+        "result": process_data(data),
+        "processed_at": datetime.now().isoformat()
+    }
+}]
+```
+
+### Pattern 3: _input.item - Each Item Mode Only
+
+**Use when**: In "Run Once for Each Item" mode
+
+```python
+# Current item in loop (Each Item mode only)
+current_item = _input.item
+
+return [{
+    "json": {
+        **current_item["json"],
+        "item_processed": True
+    }
+}]
+```
+
+### Pattern 4: _node - Reference Other Nodes
+
+**Use when**: Need data from specific nodes in workflow
+
+```python
+# Get output from specific node
+webhook_data = _node["Webhook"]["json"]
+http_data = _node["HTTP Request"]["json"]
+
+return [{
+    "json": {
+        "combined": {
+            "webhook": webhook_data,
+            "api": http_data
+        }
+    }
+}]
+```
+
+**See**: [DATA_ACCESS.md](DATA_ACCESS.md) for comprehensive guide
+
+---
+
+## Critical: Webhook Data Structure
+
+**MOST COMMON MISTAKE**: Webhook data is nested under `["body"]`
+
+```python
+# ❌ WRONG - Will raise KeyError
+name = _json["name"]
+email = _json["email"]
+
+# ✅ CORRECT - Webhook data is under ["body"]
+name = _json["body"]["name"]
+email = _json["body"]["email"]
+
+# ✅ SAFER - Use .get() for safe access
+webhook_data = _json.get("body", {})
+name = webhook_data.get("name")
+```
+
+**Why**: Webhook node wraps all request data under `body` property. This includes POST data, query parameters, and JSON payloads.
+
+**See**: [DATA_ACCESS.md](DATA_ACCESS.md) for full webhook structure details
+
+---
+
+## Return Format Requirements
+
+**CRITICAL RULE**: Always return list of dictionaries with `"json"` key
+
+### Correct Return Formats
+
+```python
+# ✅ Single result
+return [{
+    "json": {
+        "field1": value1,
+        "field2": value2
+    }
+}]
+
+# ✅ Multiple results
+return [
+    {"json": {"id": 1, "data": "first"}},
+    {"json": {"id": 2, "data": "second"}}
+]
+
+# ✅ List comprehension
+transformed = [
+    {"json": {"id": item["json"]["id"], "processed": True}}
+    for item in _input.all()
+    if item["json"].get("valid")
+]
+return transformed
+
+# ✅ Empty result (when no data to return)
+return []
+
+# ✅ Conditional return
+if should_process:
+    return [{"json": processed_data}]
+else:
+    return []
+```
+
+### Incorrect Return Formats
+
+```python
+# ❌ WRONG: Dictionary without list wrapper
+return {
+    "json": {"field": value}
+}
+
+# ❌ WRONG: List without json wrapper
+return [{"field": value}]
+
+# ❌ WRONG: Plain string
+return "processed"
+
+# ❌ WRONG: Incomplete structure
+return [{"data": value}]  # Should be {"json": value}
+```
+
+**Why it matters**: Next nodes expect list format. Incorrect format causes workflow execution to fail.
+
+**See**: [ERROR_PATTERNS.md](ERROR_PATTERNS.md) #2 for detailed error solutions
+
+---
+
+## Critical Limitation: No External Libraries
+
+**MOST IMPORTANT PYTHON LIMITATION**: Cannot import external packages
+
+### What's NOT Available
+
+```python
+# ❌ NOT AVAILABLE - Will raise ModuleNotFoundError
+import requests  # ❌ No
+import pandas  # ❌ No
+import numpy  # ❌ No
+import scipy  # ❌ No
+from bs4 import BeautifulSoup  # ❌ No
+import lxml  # ❌ No
+```
+
+### What IS Available (Standard Library)
+
+```python
+# ✅ AVAILABLE - Standard library only
+import json  # ✅ JSON parsing
+import datetime  # ✅ Date/time operations
+import re  # ✅ Regular expressions
+import base64  # ✅ Base64 encoding/decoding
+import hashlib  # ✅ Hashing functions
+import urllib.parse  # ✅ URL parsing
+import math  # ✅ Math functions
+import random  # ✅ Random numbers
+import statistics  # ✅ Statistical functions
+```
+
+### Workarounds
+
+**Need HTTP requests?**
+- ✅ Use **HTTP Request node** before Code node
+- ✅ Or switch to **JavaScript** and use `$helpers.httpRequest()`
+
+**Need data analysis (pandas/numpy)?**
+- ✅ Use Python **statistics** module for basic stats
+- ✅ Or switch to **JavaScript** for most operations
+- ✅ Manual calculations with lists and dictionaries
+
+**Need web scraping (BeautifulSoup)?**
+- ✅ Use **HTTP Request node** + **HTML Extract node**
+- ✅ Or switch to **JavaScript** with regex/string methods
+
+**See**: [STANDARD_LIBRARY.md](STANDARD_LIBRARY.md) for complete reference
+
+---
+
+## Common Patterns Overview
+
+Based on production workflows, here are the most useful Python patterns:
+
+### 1. Data Transformation
+Transform all items with list comprehensions
+
+```python
+items = _input.all()
+
+return [
+    {
+        "json": {
+            "id": item["json"].get("id"),
+            "name": item["json"].get("name", "Unknown").upper(),
+            "processed": True
+        }
+    }
+    for item in items
+]
+```
+
+### 2. Filtering & Aggregation
+Sum, filter, count with built-in functions
+
+```python
+items = _input.all()
+total = sum(item["json"].get("amount", 0) for item in items)
+valid_items = [item for item in items if item["json"].get("amount", 0) > 0]
+
+return [{
+    "json": {
+        "total": total,
+        "count": len(valid_items)
+    }
+}]
+```
+
+### 3. String Processing with Regex
+Extract patterns from text
+
+```python
+import re
+
+items = _input.all()
+email_pattern = r'\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b'
+
+all_emails = []
+for item in items:
+    text = item["json"].get("text", "")
+    emails = re.findall(email_pattern, text)
+    all_emails.extend(emails)
+
+# Remove duplicates
+unique_emails = list(set(all_emails))
+
+return [{
+    "json": {
+        "emails": unique_emails,
+        "count": len(unique_emails)
+    }
+}]
+```
+
+### 4. Data Validation
+Validate and clean data
+
+```python
+items = _input.all()
+validated = []
+
+for item in items:
+    data = item["json"]
+    errors = []
+
+    # Validate fields
+    if not data.get("email"):
+        errors.append("Email required")
+    if not data.get("name"):
+        errors.append("Name required")
+
+    validated.append({
+        "json": {
+            **data,
+            "valid": len(errors) == 0,
+            "errors": errors if errors else None
+        }
+    })
+
+return validated
+```
+
+### 5. Statistical Analysis
+Calculate statistics with statistics module
+
+```python
+from statistics import mean, median, stdev
+
+items = _input.all()
+values = [item["json"].get("value", 0) for item in items if "value" in item["json"]]
+
+if values:
+    return [{
+        "json": {
+            "mean": mean(values),
+            "median": median(values),
+            "stdev": stdev(values) if len(values) > 1 else 0,
+            "min": min(values),
+            "max": max(values),
+            "count": len(values)
+        }
+    }]
+else:
+    return [{"json": {"error": "No values found"}}]
+```
+
+**See**: [COMMON_PATTERNS.md](COMMON_PATTERNS.md) for 10 detailed Python patterns
+
+---
+
+## Error Prevention - Top 5 Mistakes
+
+### #1: Importing External Libraries (Python-Specific!)
+
+```python
+# ❌ WRONG: Trying to import external library
+import requests  # ModuleNotFoundError!
+
+# ✅ CORRECT: Use HTTP Request node or JavaScript
+# Add HTTP Request node before Code node
+# OR switch to JavaScript and use $helpers.httpRequest()
+```
+
+### #2: Empty Code or Missing Return
+
+```python
+# ❌ WRONG: No return statement
+items = _input.all()
+# Processing...
+# Forgot to return!
+
+# ✅ CORRECT: Always return data
+items = _input.all()
+# Processing...
+return [{"json": item["json"]} for item in items]
+```
+
+### #3: Incorrect Return Format
+
+```python
+# ❌ WRONG: Returning dict instead of list
+return {"json": {"result": "success"}}
+
+# ✅ CORRECT: List wrapper required
+return [{"json": {"result": "success"}}]
+```
+
+### #4: KeyError on Dictionary Access
+
+```python
+# ❌ WRONG: Direct access crashes if missing
+name = _json["user"]["name"]  # KeyError!
+
+# ✅ CORRECT: Use .get() for safe access
+name = _json.get("user", {}).get("name", "Unknown")
+```
+
+### #5: Webhook Body Nesting
+
+```python
+# ❌ WRONG: Direct access to webhook data
+email = _json["email"]  # KeyError!
+
+# ✅ CORRECT: Webhook data under ["body"]
+email = _json["body"]["email"]
+
+# ✅ BETTER: Safe access with .get()
+email = _json.get("body", {}).get("email", "no-email")
+```
+
+**See**: [ERROR_PATTERNS.md](ERROR_PATTERNS.md) for comprehensive error guide
+
+---
+
+## Standard Library Reference
+
+### Most Useful Modules
+
+```python
+# JSON operations
+import json
+data = json.loads(json_string)
+json_output = json.dumps({"key": "value"})
+
+# Date/time
+from datetime import datetime, timedelta
+now = datetime.now()
+tomorrow = now + timedelta(days=1)
+formatted = now.strftime("%Y-%m-%d")
+
+# Regular expressions
+import re
+matches = re.findall(r'\d+', text)
+cleaned = re.sub(r'[^\w\s]', '', text)
+
+# Base64 encoding
+import base64
+encoded = base64.b64encode(data).decode()
+decoded = base64.b64decode(encoded)
+
+# Hashing
+import hashlib
+hash_value = hashlib.sha256(text.encode()).hexdigest()
+
+# URL parsing
+import urllib.parse
+params = urllib.parse.urlencode({"key": "value"})
+parsed = urllib.parse.urlparse(url)
+
+# Statistics
+from statistics import mean, median, stdev
+average = mean([1, 2, 3, 4, 5])
+```
+
+**See**: [STANDARD_LIBRARY.md](STANDARD_LIBRARY.md) for complete reference
+
+---
+
+## Best Practices
+
+### 1. Always Use .get() for Dictionary Access
+
+```python
+# ✅ SAFE: Won't crash if field missing
+value = item["json"].get("field", "default")
+
+# ❌ RISKY: Crashes if field doesn't exist
+value = item["json"]["field"]
+```
+
+### 2. Handle None/Null Values Explicitly
+
+```python
+# ✅ GOOD: Default to 0 if None
+amount = item["json"].get("amount") or 0
+
+# ✅ GOOD: Check for None explicitly
+text = item["json"].get("text")
+if text is None:
+    text = ""
+```
+
+### 3. Use List Comprehensions for Filtering
+
+```python
+# ✅ PYTHONIC: List comprehension
+valid = [item for item in items if item["json"].get("active")]
+
+# ❌ VERBOSE: Manual loop
+valid = []
+for item in items:
+    if item["json"].get("active"):
+        valid.append(item)
+```
+
+### 4. Return Consistent Structure
+
+```python
+# ✅ CONSISTENT: Always list with "json" key
+return [{"json": result}]  # Single result
+return results  # Multiple results (already formatted)
+return []  # No results
+```
+
+### 5. Debug with print() Statements
+
+```python
+# Debug statements appear in browser console (F12)
+items = _input.all()
+print(f"Processing {len(items)} items")
+print(f"First item: {items[0] if items else 'None'}")
+```
+
+---
+
+## When to Use Python vs JavaScript
+
+### Use Python When:
+- ✅ You need `statistics` module for statistical operations
+- ✅ You're significantly more comfortable with Python syntax
+- ✅ Your logic maps well to list comprehensions
+- ✅ You need specific standard library functions
+
+### Use JavaScript When:
+- ✅ You need HTTP requests ($helpers.httpRequest())
+- ✅ You need advanced date/time (DateTime/Luxon)
+- ✅ You want better n8n integration
+- ✅ **For 95% of use cases** (recommended)
+
+### Consider Other Nodes When:
+- ❌ Simple field mapping → Use **Set** node
+- ❌ Basic filtering → Use **Filter** node
+- ❌ Simple conditionals → Use **IF** or **Switch** node
+- ❌ HTTP requests only → Use **HTTP Request** node
+
+---
+
+## Integration with Other Skills
+
+### Works With:
+
+**n8n Expression Syntax**:
+- Expressions use `{{ }}` syntax in other nodes
+- Code nodes use Python directly (no `{{ }}`)
+- When to use expressions vs code
+
+**n8n MCP Tools Expert**:
+- How to find Code node: `search_nodes({query: "code"})`
+- Get configuration help: `get_node_essentials("nodes-base.code")`
+- Validate code: `validate_node_operation()`
+
+**n8n Node Configuration**:
+- Mode selection (All Items vs Each Item)
+- Language selection (Python vs JavaScript)
+- Understanding property dependencies
+
+**n8n Workflow Patterns**:
+- Code nodes in transformation step
+- When to use Python vs JavaScript in patterns
+
+**n8n Validation Expert**:
+- Validate Code node configuration
+- Handle validation errors
+- Auto-fix common issues
+
+**n8n Code JavaScript**:
+- When to use JavaScript instead
+- Comparison of JavaScript vs Python features
+- Migration from Python to JavaScript
+
+---
+
+## Quick Reference Checklist
+
+Before deploying Python Code nodes, verify:
+
+- [ ] **Considered JavaScript first** - Using Python only when necessary
+- [ ] **Code is not empty** - Must have meaningful logic
+- [ ] **Return statement exists** - Must return list of dictionaries
+- [ ] **Proper return format** - Each item: `{"json": {...}}`
+- [ ] **Data access correct** - Using `_input.all()`, `_input.first()`, or `_input.item`
+- [ ] **No external imports** - Only standard library (json, datetime, re, etc.)
+- [ ] **Safe dictionary access** - Using `.get()` to avoid KeyError
+- [ ] **Webhook data** - Access via `["body"]` if from webhook
+- [ ] **Mode selection** - "All Items" for most cases
+- [ ] **Output consistent** - All code paths return same structure
+
+---
+
+## Additional Resources
+
+### Related Files
+- [DATA_ACCESS.md](DATA_ACCESS.md) - Comprehensive Python data access patterns
+- [COMMON_PATTERNS.md](COMMON_PATTERNS.md) - 10 Python patterns for n8n
+- [ERROR_PATTERNS.md](ERROR_PATTERNS.md) - Top 5 errors and solutions
+- [STANDARD_LIBRARY.md](STANDARD_LIBRARY.md) - Complete standard library reference
+
+### n8n Documentation
+- Code Node Guide: https://docs.n8n.io/code/code-node/
+- Python in n8n: https://docs.n8n.io/code/builtin/python-modules/
+
+---
+
+**Ready to write Python in n8n Code nodes - but consider JavaScript first!** Use Python for specific needs, reference the error patterns guide to avoid common mistakes, and leverage the standard library effectively.