PyCafe - Solara - Interactive Visualization of Boltzmann Wealth Model

MoneyModel.py
app.py
requirements.txt
MoneyModel.py
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"""a simple version of the boltman wealth model"""

import mesa


def compute_gini(model):
    agent_wealths = [agent.wealth for agent in model.schedule.agents]
    x = sorted(agent_wealths)
    N = model.num_agents
    B = sum(xi * (N - i) for i, xi in enumerate(x)) / (N * sum(x))
    return 1 + (1 / N) - 2 * B


class MoneyAgent(mesa.Agent):
    """An agent with fixed initial wealth."""

    def __init__(self, model):
        """initialize a MoneyAgent instance.

        Args:
            model: A model instance
        """
        super().__init__(model)
        self.wealth = 1

    def move(self):
        """move to a random neighboring cell."""
        possible_steps = self.model.grid.get_neighborhood(
            self.pos, moore=True, include_center=False
        )
        new_position = self.random.choice(possible_steps)
        self.model.grid.move_agent(self, new_position)

    def give_money(self):
        """give money to another agent in the same gridcell."""
        cellmates = self.model.grid.get_cell_list_contents([self.pos])
        if len(cellmates) > 1:
            other = self.random.choice(cellmates)
            other.wealth += 1
            self.wealth -= 1

    def step(self):
        """do one step of the agent."""
        self.move()
        if self.wealth > 0:
            self.give_money()


class MoneyModel(mesa.Model):
    """A model with some number of agents."""

    def __init__(self, n=10, width=10, height=10, seed=None):
        """Initialize a MoneyModel instance.

        Args:
            N: The number of agents.
            width: width of the grid.
            height: Height of the grid.
        """
        super().__init__(seed=seed)
        self.num_agents = n
        self.grid = mesa.space.MultiGrid(width, height, True)
        self.schedule = mesa.time.RandomActivation(self)

        # Create agents
        for _ in range(self.num_agents):
            a = MoneyAgent(self)
            self.schedule.add(a)
            # Add the agent to a random grid cell
            x = self.random.randrange(self.grid.width)
            y = self.random.randrange(self.grid.height)
            self.grid.place_agent(a, (x, y))

        self.datacollector = mesa.DataCollector(
            model_reporters={"Gini": compute_gini}, agent_reporters={"Wealth": "wealth"}
        )

    def step(self):
        """do one step of the model"""
        self.datacollector.collect(self)
        self.schedule.step()
Py.Cafe

boltzmann-wealth-model-0

Interactive Visualization of Boltzmann Wealth Model
