Add support for Observables to MESA

benchmarks/BoltzmannWealth/boltzmann_wealth.py

@@ -4,6 +4,7 @@
 """
 
 import mesa
+from mesa.experimental.signals import HasObservables, Observable
 
 
 def compute_gini(model):
@@ -74,9 +75,11 @@ def run_model(self, n):
             self.step()
 
 
-class MoneyAgent(mesa.Agent):
+class MoneyAgent(mesa.Agent, HasObservables):
     """An agent with fixed initial wealth."""
 
+    wealth = Observable()
+
     def __init__(self, model):
         """Instantiate an agent.
 

mesa/experimental/__init__.py

@@ -1,7 +1,8 @@
 """Experimental init."""
 
+import mesa.experimental.signals as signals
 from mesa.experimental import cell_space
 
-from .solara_viz import JupyterViz, Slider, SolaraViz, make_text
+# from .solara_viz import JupyterViz, Slider, SolaraViz, make_text
 
-__all__ = ["cell_space", "JupyterViz", "SolaraViz", "make_text", "Slider"]
+__all__ = ["cell_space", "signals"]

mesa/experimental/cell_space/cell_agent.py

@@ -4,9 +4,10 @@
 
 from typing import TYPE_CHECKING
 
-from mesa import Agent, Model
+from mesa import Agent
 
 if TYPE_CHECKING:
+    from mesa import Model
     from mesa.experimental.cell_space.cell import Cell
 
 

mesa/experimental/signals/__init__.py

@@ -0,0 +1,13 @@
+"""Functionality for Observables."""
+
+from .observable_collections import ObservableList
+from .signal import All, Computable, Computed, HasObservables, Observable
+
+__all__ = [
+    "Observable",
+    "ObservableList",
+    "HasObservables",
+    "All",
+    "Computable",
+    "Computed",
+]

mesa/experimental/signals/observable_collections.py

@@ -0,0 +1,120 @@
+"""This module defines observable collections classes.
+
+Observable collections behave like Observable but then for collections.
+
+
+"""
+
+from collections.abc import Iterable, MutableSequence
+from typing import Any
+
+from .signal import BaseObservable, HasObservables
+
+__all__ = [
+    "ObservableList",
+]
+
+
+class ObservableList(BaseObservable):
+    """An ObservableList that emits signals on changes to the underlying list."""
+
+    def __init__(self):
+        """Initialize the ObservableList."""
+        super().__init__()
+        self.signal_types: set = {
+            "added",
+            "removed",
+            "replaced",
+            "on_change",
+        }
+        self.fallback_value = []
+
+    def __set__(self, instance: "HasObservables", value: Iterable):
+        """Set the value of the descriptor attribute.
+
+        Args:
+            instance: The instance on which to set the attribute.
+            value: The value to set the attribute to.
+
+        """
+        super().__set__(instance, value)
+        setattr(
+            instance,
+            self.private_name,
+            SignalingList(value, instance, self.public_name),
+        )
+
+
+class SignalingList(MutableSequence[Any]):
+    """A basic lists that emits signals on changes."""
+
+    __slots__ = ["owner", "name", "data"]
+
+    def __init__(self, iterable: Iterable, owner: HasObservables, name: str):
+        """Initialize a SignalingList.
+
+        Args:
+            iterable: initial values in the list
+            owner: the HasObservables instance on which this list is defined
+            name: the attribute name to which  this list is assigned
+
+        """
+        self.owner: HasObservables = owner
+        self.name: str = name
+        self.data = list(iterable)
+
+    def __setitem__(self, index: int, value: Any) -> None:
+        """Set item to index.
+
+        Args:
+            index: the index to set item to
+            value: the item to set
+
+        """
+        old_value = self.data[index]
+        self.data[index] = value
+        self.owner.notify(self.name, old_value, value, "replaced")
+
+    def __delitem__(self, index: int) -> None:
+        """Delete item at index.
+
+        Args:
+            index: The index of the item to remove
+
+        """
+        old_value = self.data
+        del self.data[index]
+        self.owner.notify(self.name, old_value, None, "removed")
+
+    def __getitem__(self, index) -> Any:
+        """Get item at index.
+
+        Args:
+            index: The index of the item to retrieve
+
+        Returns:
+            the item at index
+        """
+        return self.data[index]
+
+    def __len__(self) -> int:
+        """Return the length of the list."""
+        return len(self.data)
+
+    def insert(self, index, value):
+        """Insert value at index.
+
+        Args:
+            index: the index to insert value into
+            value: the value to insert
+
+        """
+        old_value = self.data[index]
+        self.data.insert(index, value)
+        self.owner.notify(self.name, old_value, value, "added")
+
+    def __str__(self):
+        return self.data.__str__()
+
+    def __repr__(self):
+        return self.data.__repr__()