[New] Python Abstract Classes

content/blog/pythonabstractclass.md

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+---
+title: "Quick Python: Abstract Classes"
+date: 2020-01-26T18:40:03-05:00
+draft: false
+images: []
+---
+
+You can create an abstract class in Python by inheriting Abstract Base Class (`ABC`) and declaring relevant methods abstract.
+
+First import the following from the standard library,
+
+```python
+from abc import ABC, abstractmethod
+```
+
+Then create an abstract class, making sure to add the decorator `@abstractmethod` to the constructor. This prevents the user from instantiating the class.
+
+```python
+class Animal:
+    @abstractmethod
+    def __init__(self, name):
+        self.name = name
+    @abstractmethod
+    def is_bipedal(self):
+        pass
+    def speak(self):
+        return "Hello my name is " + self.name + " and I am a " + type(self).__name__
+```
+
+In the example above:
+
+- A constructor is made, however, the class Animal cannot be instantiated. Do note that child classes can call the constructor.
+- `is_bipedal` is an abstract method that needs to be defined in child classes. `pass` indicates that it is not implemented.
+- `speak` is a normal method that will be inherited by child classes.
+
+Now let's look at a class that inherits `Animal`.
+
+```python
+class Dog(Animal):
+    def __init__(self, name, owner):
+        super().__init__(name) # Calls Animal constructor
+        self.owner = owner
+    def is_bipedal(self):
+        return False
+```
+