Markdown updates

Author: dancergraham

chapter09_iterator/readme.md

@@ -1,5 +1,16 @@
-# Chapter 8: Iterator design pattern
+# Chapter 9: Iterator and Composite design patterns
 
-> **Template Method**: provides a way to access the elements of an aggregate object sequentially without exposing its underlying representation.
+> **Iterator Method**: provides a way to access the elements of an aggregate object sequentially without exposing its underlying representation.
 
 Python requires only the `__iter__()` method to be implemented for an object to return `True` to `isinstance(obj, Iterable)`, however if an object implements just the `__getitem__()` without `__iter__` method then it will work as an  iterable!
+
+> **Composite Pattern**: allows you to compose objects into tree structures to represent whole-part hierarchies.  Composite lets clients treat individual objects and compositions of objects uniformly.
+
+A pythonic alternative would be to:
+
+```python
+try: 
+    composition_method()
+except CompositionMethodError:
+    individual_method()
+```