Merge pull request #11 from leapfrogtechnology/python

Python Changes

Author: anishmanandhar

docs/python/classes.md

@@ -8,6 +8,20 @@ sidebar_label: Classes
 
 * Avoid inbuilt names.
 * Classes names should always be `PascalCase`. i.e. `MyClass` 
-* Even if you are building datatypes based on inbuilt class use PascalCase. i.e. `MyDict(dict):`
-* Describe the class resposibility in name.
+* **Abstract Classes and Mixins**
+    + Use [abstract containers](https://docs.python.org/3/library/collections.abc.html#module-collections.abc) if need to override datatypes.
+        - If you must build datatypes based on inbuilt class use PascalCase. i.e. `MyDict(dict):`.
+    + Use [`abc`](https://docs.python.org/3/library/abc.html) if you need pure OOP style abstract classes. Use `NotImplementedError` exceptions with overrides.
+    + mixin should be named with `Mixin` suffix such as `class LoginRequiredMixin` which can be used in multiple inheritance.
+* Describe the class responsibility in name.
 * Custom Exceptions should always be named ending with `Error` i.e. `MyCustomError`
+
+##### Example
+
+```python
+class HelloWorld:
+    pass
+    
+class HelloWorldError(Exception):
+    pass
+```