UML Diagram Demo

Demonstrates the live UML class diagram and sequence diagram feature.

1

Class Hierarchy

Live UML Diagrams

This tutorial demonstrates the UML Diagram tab. Look at the tab bar above the editor — you should see a UML Diagram tab.

The code editor defines a simple class hierarchy: Animal is the base class, with Dog and Cat as subclasses.

Try it:

  1. Click the UML Diagram tab to see the class diagram.
  2. Edit the code — add a new method or attribute — and watch the diagram update.
  3. Switch between Class Diagram and Sequence Diagram using the toolbar buttons.
Starter files
animals.py
class Animal:
    def __init__(self, name: str):
        self.name: str = name

    def speak(self) -> str:
        return "..."

class Dog(Animal):
    def __init__(self, name: str, breed: str):
        super().__init__(name)
        self.breed: str = breed

    def speak(self) -> str:
        return "Woof!"

    def fetch(self, item: str) -> str:
        return f"{self.name} fetches {item}"

class Cat(Animal):
    def __init__(self, name: str, indoor: bool):
        super().__init__(name)
        self.indoor: bool = indoor

    def speak(self) -> str:
        return "Meow!"

if __name__ == "__main__":
    dog = Dog("Rex", "Labrador")
    cat = Cat("Whiskers", True)
    print(dog.speak())
    print(cat.speak())
2

Composition & Sequence

Composition Relationships

Now we have a Zoo class that contains animals — this is a composition relationship, shown as a filled diamond arrow in the class diagram.

The sequence diagram shows the call flow: Zoo.add_animal() and Zoo.roll_call() calling speak() on each animal.

Try it:

  1. Switch to the UML Diagram tab.
  2. Toggle between Class Diagram and Sequence Diagram.
  3. Add a new method to Zoo and watch both diagrams update.
Starter files
animals.py
class Animal:
    def __init__(self, name: str):
        self.name: str = name

    def speak(self) -> str:
        return "..."

class Dog(Animal):
    def __init__(self, name: str, breed: str):
        super().__init__(name)
        self.breed: str = breed

    def speak(self) -> str:
        return "Woof!"

    def fetch(self, item: str) -> str:
        return f"{self.name} fetches {item}"

class Cat(Animal):
    def __init__(self, name: str, indoor: bool):
        super().__init__(name)
        self.indoor: bool = indoor

    def speak(self) -> str:
        return "Meow!"

if __name__ == "__main__":
    dog = Dog("Rex", "Labrador")
    cat = Cat("Whiskers", True)
    print(dog.speak())
    print(cat.speak())
zoo.py
from animals import Animal, Dog, Cat

class Zoo:
    def __init__(self, name: str):
        self.name: str = name
        self.animals: list = []

    def add_animal(self, animal: Animal):
        self.animals.append(animal)

    def roll_call(self):
        for animal in self.animals:
            print(f"{animal.name}: {animal.speak()}")

if __name__ == "__main__":
    zoo = Zoo("City Zoo")
    zoo.add_animal(Dog("Rex", "Lab"))
    zoo.add_animal(Cat("Whiskers", True))
    zoo.roll_call()