Fixed #4: string formatting

Author: programmdesign

docs/correctness/method_could_be_a_function.rst

@@ -66,7 +66,7 @@ All class methods must be preceded by the ``@classmethod`` decorator. Furthermor
     class Rectangle:
         @classmethod
         def print_class_name(cls):
-            print("class name: %s" % cls) # "class name: Rectangle"
+            print("class name: {0}".format(cls)) # "class name: Rectangle"
 
 References
 ----------

docs/correctness/method_has_no_argument.rst

@@ -28,7 +28,7 @@ The method ``print_class_name`` attempts to print the name of the class. However
     class Rectangle:
         @classmethod
         def print_class_name(): # missing first argument "cls"
-            print("Hello, I am %s!" % cls) # cls is undefined here
+            print("Hello, I am {0}!".format(cls)) # cls is undefined here
 
 
 The method ``area`` computes the value of any rectangle. Currently this method is ambiguous. It is defined as a method of the ``Rectangle`` class, yet it does not reference any instance or class members. The method needs to explicitly state that it is a static method via the ``@staticmethod`` decorator.
@@ -68,7 +68,7 @@ To access the name of the class the ``print_class_name`` method needs to explici
     class Rectangle:
         @classmethod
         def print_class_name(cls): # class members now accessible, thanks to "cls"
-            print("Hello, I am %s!" % cls)
+            print("Hello, I am {0}!".format(cls))
 
 Add the ``@staticmethod`` decorator to static methods
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