Update strategy to mark the behaviour as private

Author: GrahamKnappAcernis

README.md

@@ -71,23 +71,23 @@ From this repository :
 
 ```python
 class Duck():
-    fly_behavior = None
-    quack_behavior = None
+    _fly_behavior = None
+    _quack_behavior = None
 
     def set_fly_behavior(self, fly_behavior):
-        self.fly_behavior = fly_behavior
+        self._fly_behavior = fly_behavior
 
     def set_quack_behavior(self, quack_behavior):
-        self.quack_behavior = quack_behavior
+        self._quack_behavior = quack_behavior
 
-    def display():
+    def display(self):
         raise NotImplementedError
 
     def perform_fly(self):
-        self.fly_behavior.fly()
+        self._fly_behavior.fly()
 
     def perform_quack(self):
-        self.quack_behavior.quack()
+        self._quack_behavior.quack()
 
     def swim(self):
         print("All ducks float, even decoys! 〰🦆〰")

chapter01_strategy/duck.py

@@ -39,39 +39,39 @@ def quack(self):
 
 
 class Duck:
-    fly_behavior = None
-    quack_behavior = None
+    _fly_behavior = None
+    _quack_behavior = None
 
     def set_fly_behavior(self, fly_behavior):
-        self.fly_behavior = fly_behavior
+        self._fly_behavior = fly_behavior
 
     def set_quack_behavior(self, quack_behavior):
-        self.quack_behavior = quack_behavior
+        self._quack_behavior = quack_behavior
 
-    def display():
+    def display(self):
         raise NotImplementedError
 
     def perform_fly(self):
-        self.fly_behavior.fly()
+        self._fly_behavior.fly()
 
     def perform_quack(self):
-        self.quack_behavior.quack()
+        self._quack_behavior.quack()
 
-    def swim():
+    def swim(self):
         print("All ducks float, even decoys!")
 
 
 class MallardDuck(Duck):
-    fly_behavior = FlyWithWings()
-    quack_behavior = Quack()
+    _fly_behavior = FlyWithWings()
+    _quack_behavior = Quack()
 
     def display(self):
         print("I'm a real Mallard duck")
 
 
 class ModelDuck(Duck):
-    fly_behavior = FlyNoWay()
-    quack_behavior = Squeak()
+    _fly_behavior = FlyNoWay()
+    _quack_behavior = Squeak()
 
     def display(self):
         print("I'm a real Mallard duck")

chapter01_strategy/readme.md

@@ -1,6 +1,7 @@
 # Chapter 1: Strategy design pattern
 
-> **Strategy**: defines a family of algorithms, encapsulates each one and makes them interchangeable. Strategy lets the algorithm vary independently from clients that use it.
+> **Strategy**: defines a family of algorithms, encapsulates each one and makes them interchangeable. 
+> Strategy lets the algorithm vary independently of clients that use it.
 
 ### Class Diagram
 
@@ -28,6 +29,13 @@ Strategy "1" <|.. "*" ConcreteStrategyB
 
 ## Use in Python
 
-The more pythonic approach in my mind is to define methods rather than classes; this does not violate the above definition.  The class-based approach is needed in Java and has the advantage of explicitly setting out the required method in an abstract base class.
+The more pythonic approach in my mind is to define methods rather than classes; 
+this does not violate the above definition.  The class-based approach is 
+needed in Java and has the advantage of explicitly setting out the required 
+method in an abstract base class.
 
-An example from the standard lib is the list `sort()` and `sorted()` methods with the use of an optional `key` parameter.  They invite the use of a sorting function or sorting "strategy", as do `min()` and `max()`. 
+An example from the standard lib is the list `sort()` and `sorted()` methods 
+with the use of an optional `key` parameter.  They invite the use of a sorting 
+function or sorting "strategy", as do `min()` and `max()`, although this might
+be better seen as a template method as the `key` function is just one part of 
+the sorting or min/max algorithm.