This book is now obsolete Please use CSAwesome instead.
11.16. Common Mistakes¶
Using inheritance (is a kind of) when you should use association (has a). A school has classes, it is not a type of class. A high school is a kind of school.
Using a type field instead of subclasses. If you ever find yourself creating conditionals based on the type of object use subclasses instead.
Copying code instead of creating a subclass or pulling out a common superclass. If you ever find yourself copying object fields or methods try creating a subclass instead or pull out a common superclass.