Prerequisites
Claude Desktop app installed
Pylance MCP Server running
Anthropic account with API access
Quick Start
Install Pylance MCP
Install via pip: pip install pylance-mcp-server
Configure Claude
Edit Claude Desktop configuration: macOS : ~/Library/Application Support/Claude/claude_desktop_config.jsonWindows : %APPDATA%\Claude\claude_desktop_config.jsonLinux : ~/.config/Claude/claude_desktop_config.json{ "mcpServers" : { "pylance" : { "command" : "python" , "args" : [ "-m" , "pylance_mcp.server" ], "env" : { "PYLANCE_WORKSPACE" : "/path/to/your/python/project" } } } }
Restart Claude Desktop
Quit and reopen Claude Desktop app
Verify Setup
In Claude chat, type: Can you analyze my Python workspace?
Claude should respond with workspace information. Configuration Examples Single Workspace claude_desktop_config.json
{ "mcpServers" : { "pylance" : { "command" : "python" , "args" : [ "-m" , "pylance_mcp.server" ], "env" : { "PYLANCE_WORKSPACE" : "/Users/you/projects/myapp" , "PYTHONPATH" : "/Users/you/projects/myapp" } } } }
Multiple Workspaces claude_desktop_config.json
{ "mcpServers" : { "pylance-backend" : { "command" : "python" , "args" : [ "-m" , "pylance_mcp.server" , "--port" , "3000" ], "env" : { "PYLANCE_WORKSPACE" : "/Users/you/projects/backend" } }, "pylance-ml" : { "command" : "python" , "args" : [ "-m" , "pylance_mcp.server" , "--port" , "3001" ], "env" : { "PYLANCE_WORKSPACE" : "/Users/you/projects/ml-models" } } } }
Cloud-Hosted claude_desktop_config.json
{ "mcpServers" : { "pylance" : { "url" : "https://api.pylancemcp.dev" , "headers" : { "Authorization" : "Bearer YOUR_API_KEY" , "X-Workspace" : "/path/to/workspace" } } } }
Usage Examples Code Review Ask Claude to review your code:
@pylance review the authentication module in src/auth.py
Claude will analyze:
Type safety issues
Potential bugs
Security vulnerabilities
Code style consistency
Best practice violations
Refactoring Assistance Request refactoring help:
@pylance can you help refactor database.py to use async/await?
Claude will:
Analyze current implementation
Suggest refactoring approach
Generate refactored code
Explain changes made
Documentation Generation Generate docstrings:
@pylance generate docstrings for all functions in utils.py
Output:
def calculate_total ( items : List[Item]) -> float : """ Calculate the total price of all items. Args: items: List of Item objects containing price information Returns: float: Sum of all item prices Raises: ValueError: If items list is empty Example: >>> items = [Item(price=10.0), Item(price=20.0)] >>> calculate_total(items) 30.0 """ if not items: raise ValueError ( "Items list cannot be empty" ) return sum (item.price for item in items)
Test Generation Generate unit tests:
@pylance create pytest tests for the User class in models/user.py
Claude generates comprehensive tests including:
Happy path scenarios
Edge cases
Error handling
Fixtures and mocks
Advanced Features Context-Aware Conversations Claude maintains context across messages:
You: @pylance what's the User model structure? Claude: The User model has email, password_hash, created_at fields... You: Add a last_login field to it Claude: I'll add the last_login timestamp field to the User model...
Multi-File Analysis Analyze dependencies across files:
@pylance trace how the login function works from API endpoint to database
Claude maps the flow:
api/auth.py:login_endpoint() → services/auth.py:authenticate_user() → models/user.py:User.verify_password() → database.py:query_user_by_email()
Intelligent Code Search Search using natural language:
@pylance find all database queries that aren't using prepared statements
Claude locates potential SQL injection vulnerabilities.
Conversation Templates Bug Investigation @pylance I'm getting a TypeError on line 45 of main.py. The error message is: "unsupported operand type(s) for +: 'int' and 'str'" Can you help debug this?
Feature Implementation @pylance I need to add OAuth2 authentication to the API. Can you: 1. Show me what files need to be modified 2. Generate the necessary code 3. Explain the security considerations
@pylance This function is slow with large datasets: [paste code] Can you suggest optimizations and show benchmarks?
Troubleshooting
Error : Command 'python' not foundFix : Use absolute path to Python:{ "command" : "/usr/local/bin/python3" , "args" : [ "-m" , "pylance_mcp.server" ] }
Error : Failed to initialize workspaceChecklist :
✅ Workspace path exists
✅ Path has no trailing slash
✅ User has read permissions
✅ Contains Python files (.py)
Error : 401 UnauthorizedSolutions :
Check API key is valid
Verify subscription is active
Ensure API key has correct permissions
Symptoms : No response to @pylance commandsDebug :
Check Claude Desktop logs:
macOS: ~/Library/Logs/Claude/
Windows: %APPDATA%\Claude\logs\
Verify MCP server is running:
ps aux | grep pylance_mcp
Test server manually:
python -m pylance_mcp.server --test
Large Workspaces For projects with >5,000 files:
claude_desktop_config.json
{ "mcpServers" : { "pylance" : { "command" : "python" , "args" : [ "-m" , "pylance_mcp.server" , "--max-workers" , "4" , "--cache-dir" , "/tmp/pylance-cache" ], "env" : { "PYLANCE_WORKSPACE" : "/path/to/large/project" , "PYLANCE_DIAGNOSTIC_MODE" : "openFilesOnly" } } } }
Memory Limits Constrain memory usage:
{ "env" : { "PYLANCE_MAX_MEMORY" : "2048" , // MB "PYLANCE_CACHE_SIZE" : "500" // MB } }
Security Best Practices Never commit claude_desktop_config.json with API keys to version control
Use environment variables:
claude_desktop_config.json
{ "mcpServers" : { "pylance" : { "url" : "https://api.pylancemcp.dev" , "headers" : { "Authorization" : "Bearer ${PYLANCE_API_KEY}" } } } }
Set in shell profile:
export PYLANCE_API_KEY = "pk_live_..."
Tips & Tricks Tip 1 : Use @pylance at the start of messages for better context
Tip 2 : Reference specific files: @pylance analyze src/models/user.py
Tip 3 : Ask for alternatives: @pylance show 3 ways to implement this function
Tip 4 : Request explanations: @pylance explain this decorator pattern
Next Steps 
