Fix: add actual implementation for use-effect simulation (previous PR was empty)

dynamic_programming/use_effect_simulation.py

@@ -0,0 +1,40 @@
+"""
+Simulation of a simple useEffect-like behavior in Python.
+
+This demonstrates executing a function when a dependency changes.
+Reference:
+https://en.wikipedia.org/wiki/Reactive_programming
+"""
+
+from typing import Callable, Any
+
+
+def use_effect_simulation(callback: Callable[[], None], dependency: Any) -> None:
+    """
+    Executes the callback when the dependency changes.
+
+    >>> calls = []
+    >>> def cb():
+    ...     calls.append("called")
+    >>> use_effect_simulation(cb, 1)
+    >>> use_effect_simulation(cb, 1)
+    >>> use_effect_simulation(cb, 2)
+    >>> calls
+    ['called', 'called']
+    """
+    if not hasattr(use_effect_simulation, "_prev"):
+        use_effect_simulation._prev = None  # type: ignore
+
+    if use_effect_simulation._prev != dependency:
+        callback()
+        use_effect_simulation._prev = dependency
+
+
+if __name__ == "__main__":
+
+    def example():
+        print("Effect triggered!")
+
+    use_effect_simulation(example, 1)
+    use_effect_simulation(example, 1)
+    use_effect_simulation(example, 2)