mermaidgenerator 1.3.0

Generator to create mermaid class diagrams.

MermaidGenerator

Automatically generate Mermaid class diagrams from Python source code.

MermaidGenerator parses your Python files using the AST and produces a Markdown file with embedded Mermaid class diagrams — no runtime execution required. See an example output.

Made by Fabian Gnatzig in 2026.

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Features

• Class attributes with type annotations
• Method signatures including argument types and return types
• Inheritance relationships with links between diagrams
• @staticmethod and @classmethod — marked with $
• @abstractmethod — marked with *
• @property — rendered as a typed attribute, backing field suppressed
• Abstract base classes (ABC) — rendered with <<abstract>> stereotype
• @dataclass and other decorators — rendered as Mermaid stereotypes
• Public (+) and private (-) visibility based on naming convention
• Union types (X | Y), generics (list[str]), and qualified types (typing.Optional)
• Works on single files or entire project trees

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Installation

pip install mermaidgenerator

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Usage

python -m mermaidgenerator --src-folder <path> [--doc-path <output>]

Argument	Required	Description
--src-folder	yes	Root directory of your Python project to scan
--doc-path	no	Output path for the .md file (default: <src-folder>/../class_diagrams.md)
--exclude	no	Glob pattern of files to skip, relative to --src-folder (can be repeated)

Examples

# Basic usage
python -m mermaidgenerator --src-folder src --doc-path docs/class_diagrams.md

# Exclude test files and a specific module
python -m mermaidgenerator --src-folder src --exclude "**/test_*.py" --exclude "migrations/*.py"

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Use as a pre-commit hook

Add this to your project's .pre-commit-config.yaml:

- repo: https://github.com/FabianGnatzig/MermaidGenerator
  rev: v1.2.1
  hooks:
    - id: mermaidgenerator
      args: [--src-folder, src, --doc-path, docs/class_diagrams.md]

args accepts the same flags as the CLI (--src-folder, --doc-path, --exclude). Pin rev to a tag and run pre-commit autoupdate to bump it later.

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Example output

Given a class like this:

from abc import ABC, abstractmethod

class Shape(ABC):
    """Abstract base class for shapes."""

    def __init__(self, color: str) -> None:
        self.color: str = color

    @abstractmethod
    def area(self) -> float: ...

    @staticmethod
    def describe(color: str) -> str: ...

MermaidGenerator produces:

# Shape
Abstract base class for shapes.
```mermaid
classDiagram
    class Shape {
<<abstract>>
+ str color
- __init__(color: str) None
+ area() float *
+ describe(color: str) str $
}
```