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C4 Literate Python

Generate C4 architecture diagrams from literate Python code. View source on GitHub

Project Overview

C4 Literate Python extracts C4 model annotations from well-documented Python codebases and generates Structurizr DSL for creating architecture diagrams. Following literate programming principles, architecture documentation lives alongside the code it describes - no separate diagram files to maintain and no drift between code and documentation.

Technology Stack

Technology Role
Python 3.12 Core language (stdlib only - zero runtime dependencies)
ast module Python source code parsing
re module Annotation extraction from docstrings
Structurizr DSL Output format for C4 architecture diagrams
YAML / JSON Annotation schema definition

Key Features

  • Embed architecture documentation directly in Python docstrings
  • Automatic Structurizr DSL generation from annotations
  • Validation of C4 annotations before generation
  • Support for Container and Component diagrams
  • Zero runtime dependencies (Python standard library only)
  • PEP8-compliant multi-line annotation handling

Annotation Schema

Container Declaration

"""
@c4-container: API Application
@c4-technology: Python 3.12, FastAPI
@c4-description: Main REST API server
@c4-responsibilities:
    - Handle HTTP requests
    - Validate input data
"""

Component Declaration

"""
@c4-component: Authentication Service
@c4-technology: JWT, bcrypt
@c4-description: Handles user authentication
"""

Relationships

"""
@c4-uses: Database Layer - "Reads/writes data" - "SQLAlchemy"
@c4-used-by: API Gateway - "Routes requests" - "HTTP"
@c4-used-by-person: End User - "Makes API calls" - "HTTPS"
"""

Operations (Function Level)

def create_user(user_data):
    """
    @c4-operation: create_user
    @c4-calls: Database Layer - "Persists user record"
    """
    pass

Schema Reference

Full annotation schema is documented in:

  • Source of Truth: c4-annotations-schema.yaml (edit this file)
  • User Documentation: SCHEMA.md (generated from YAML)

Key annotations: @c4-container, @c4-component, @c4-technology, @c4-description, @c4-uses, @c4-calls, @c4-operation

Design Philosophy

Literate Programming

  • Architecture documentation lives with code
  • Annotations are human-readable
  • No separate diagram files to maintain
  • Documentation evolves with code

Minimal Dependencies

Core tool uses only Python standard library (ast for parsing, re for extraction). No external dependencies required.

PEP8 Compliance

Handles multi-line annotations wrapped at 79 characters. The tangler automatically rejoins these into single-line descriptions for clean DSL generation.

Codebase Overview

c4-literate-python/
├── src/
│   └── c4_literate/             # Main package: parser, tangler, validator, CLI
├── tests/                       # Unit tests for annotation extraction and DSL generation
├── docs/                        # ADRs and design documentation
├── c4-annotations-schema.yaml   # Source of truth for annotation schema
├── c4-annotations-schema.json   # JSON version of annotation schema
├── SCHEMA.md                    # Generated schema documentation
├── USAGE_EXAMPLE.md             # Annotated codebase walkthrough
├── generate_schema_docs.py      # Script to regenerate SCHEMA.md from YAML
├── workspace.dsl                # Example Structurizr DSL output
├── Makefile                     # Build targets: test, lint, docs
├── pyproject.toml               # Package configuration and dependencies
└── README.md                    # This file

Future Work

  • System Context diagram support
  • Deployment diagram support
  • Export to other formats (PlantUML, Mermaid)
  • MkDocs integration (weaver)
  • VS Code extension for real-time validation
  • Multi-workspace support for monorepos

Resources