Design Pattern Examples in Python

Model and code examples of GoF Design Patterns for Python.
This project is available for the following objectives:

• To understand GoF Design Pattern examples in Python.
• To understand the mapping between UML model and Python code.
• To try Model-Driven Development (MDD) using Astah and M PLUS plug-in.

UML model example:

Python code example:

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# ˅
from structural_patterns.composite.file_system_element import FileSystemElement

# ˄


class File(FileSystemElement):
    # ˅

    # ˄

    def __init__(self, name, size):

        self.__name = name

        self.__size = size

        # ˅
        super().__init__()
        # ˄

    def get_name(self):
        # ˅
        return self.__name
        # ˄

    def get_size(self):
        # ˅
        return self.__size
        # ˄

    # Print this element with the "upper_path".
    def print(self, upper_path):
        # ˅
        print(upper_path + '/' + self.to_string())
        # ˄

    # ˅

    # ˄


# ˅

# ˄

Installation

UML Modeling Tool

• Download the modeling tool Astah UML or Professional, and install.
• Download M PLUS plug-in ver.2.1 or higher, and add it to Astah.
  How to add plugins to Astah

Python Development Environment

• Install Python with tkinter included. The operation has been confirmed in Python 3.12.2.
• Optionally, install an IDE (e.g. PyCharm).

Usage

Code Generation from UML

1. Open the Astah file (model/DesignPatternExamplesInPython.asta).
2. Select model elements on the model browser of Astah.
3. Click the Generate Code button.
   
   The generated code has User Code Area. The User Code Area is the area enclosed by "˅" and "˄". Handwritten code written in the User Code Area remains after a re-generation. View code example.
   For detailed usage of the tools, please see Astah Manual and M PLUS plug-in Tips.

Run (if you use PyCharm)

1. Open the project root directory (design-pattern-examples-in-python) in PyCharm.
2. Open main.py for the pattern you want to run, and click Run icon in the left gutter.

References

• Gamma, E. et al. Design Patterns: Elements of Reusable Object-Oriented Software, Addison-Wesley, 1994
• Hiroshi Yuki. Learning Design Patterns in Java [In Japanese Language], Softbank publishing, 2004

Licence

This project is licensed under the Creative Commons Zero (CC0) license. The model and code are completely free to use.

Other Language Examples

C++, C#, Crystal, Go, Java, JavaScript, Kotlin, Ruby, Scala, Swift, TypeScript