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Implements comprehensive Python Code node guidance with critical focus on "NO external libraries" limitation. ## Skill #7 - n8n Code Python **Critical Message**: Use JavaScript for 95% of use cases. Python in n8n has NO external libraries (no requests, pandas, numpy). ### Files Created **Core Skill Files (6 files, 4,205 lines total)**: 1. **SKILL.md** (748 lines) - When to use Python vs JavaScript (95% JavaScript recommendation) - Critical limitation: NO external libraries - Mode selection (All Items vs Each Item) - Data access overview (_input, _json, _node) - Return format requirements - Standard library overview 2. **DATA_ACCESS.md** (702 lines) - _input.all() - Process all items - _input.first() - Get first item - _input.item - Current item (Each Item mode only) - _node["Name"] - Reference other nodes - Webhook body structure (data under ["body"]) - Pattern selection guide - Python vs JavaScript comparison 3. **STANDARD_LIBRARY.md** (974 lines) - Complete reference for available modules - json - JSON parsing and generation - datetime - Date/time operations - re - Regular expressions - base64 - Encoding/decoding - hashlib - Hashing (MD5, SHA256) - urllib.parse - URL operations - math, random, statistics - What's NOT available (requests, pandas, numpy, etc.) - Workarounds for missing libraries 4. **COMMON_PATTERNS.md** (794 lines) - 10 production-tested Python patterns - Multi-source data aggregation - Regex-based filtering - Markdown to structured data - JSON object comparison - CRM data transformation - Release notes processing - Array transformation - Dictionary lookup - Top N filtering - String aggregation - Python vs JavaScript pattern comparison 5. **ERROR_PATTERNS.md** (601 lines) - Top 5 Python-specific errors with solutions - Error #1: ModuleNotFoundError (THE critical Python error) - Error #2: Empty code / missing return - Error #3: KeyError (use .get() instead) - Error #4: IndexError (check bounds first) - Error #5: Incorrect return format - Error prevention checklist - Quick fix reference table - Testing patterns 6. **README.md** (386 lines) - Skill metadata and activation triggers - "JavaScript First" recommendation prominent - What this skill teaches - File structure overview - Integration with other skills - Success metrics checklist - Quick reference guide - Common use cases - Limitations and workarounds - Best practices **Evaluations (5 scenarios)**: 1. **eval-001-module-import-error.json** - Tests understanding of external library limitation - Scenario: ModuleNotFoundError with requests - Expected: Recommend JavaScript or HTTP Request node 2. **eval-002-dictionary-keyerror.json** - Tests safe dictionary access with .get() - Scenario: KeyError when accessing missing field - Expected: Use .get() with default values 3. **eval-003-webhook-body-gotcha.json** - Tests webhook data under ["body"] understanding - Scenario: KeyError when accessing webhook data directly - Expected: Access via data.get("body", {}) 4. **eval-004-return-format-error.json** - Tests proper return format requirement - Scenario: Returning plain dict instead of array - Expected: Return [{"json": {...}}] 5. **eval-005-standard-library-usage.json** - Tests knowledge of available modules - Scenario: What modules for JSON, hashing, dates, regex - Expected: json, hashlib, datetime, re (standard library only) ### Key Features **Critical Limitations Emphasized**: - NO external libraries (no requests, pandas, numpy) - JavaScript recommended for 95% of use cases - Only standard library available - ModuleNotFoundError is #1 Python error **Python-Specific Syntax**: - Underscore prefix: _input, _json, _node (vs $ in JavaScript) - Dictionary access: _json["body"]["field"] (vs dot notation) - Safe access: .get() method with defaults **Complete Standard Library Coverage**: - 15+ modules documented with examples - json, datetime, re, base64, hashlib, urllib.parse - math, random, statistics, collections - Clear list of what's NOT available - Workarounds for missing functionality **Production Patterns**: - 10 tested patterns adapted from JavaScript - Python-specific implementations - List comprehensions and dictionary operations - Standard library usage examples **Error Prevention Focus**: - Top 5 errors cover majority of failures - ModuleNotFoundError prominently featured - Safe dictionary access (.get()) - Proper return format emphasized - Error prevention checklist ### Integration Works seamlessly with: - **n8n Code JavaScript**: Compare approaches, know when to use which - **n8n Expression Syntax**: Different from {{}} expressions - **n8n MCP Tools Expert**: Validate Code node configurations - **n8n Workflow Patterns**: Code nodes in larger workflows - **n8n Node Configuration**: Configure mode and connections ### Statistics - **6 skill files**: 4,205 lines total - **5 evaluations**: Cover critical Python scenarios - **10 patterns**: Production-tested Python code - **15+ modules**: Standard library coverage - **5 top errors**: Prevention and solutions ### Design Principles 1. **JavaScript First**: 95% recommendation throughout 2. **Critical Limitation**: NO external libraries emphasized everywhere 3. **Safe Patterns**: .get() for dicts, bounds checking for lists 4. **Proper Format**: [{"json": {...}}] return format 5. **Standard Library**: Complete reference with examples 6. **Error Prevention**: Top 5 errors with solutions ### Recommendation **Use JavaScript Code node for 95% of use cases.** Use Python only when: - Complex Python-specific logic required - Python standard library features needed - Team more comfortable with Python than JavaScript For HTTP requests, date operations, and most transformations → Use JavaScript. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com> Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en