Simple classes tutorial

Python/040_classes.py

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+# Tutorial demonstrating the use of classes in Python
+
+# Note: The subject of classes in Python is both broad and quite complex.
+#       This should serve as a simple example of how to use classes,
+#       objects created from them, and how to access their attributes
+#       and methods. Further research online, and personal experimentation
+#       is HIGHLY recommended.
+
+# A class that describes a Person
+class Person():
+    # This is a class variable. It can be accessed both from the base class
+    # i.e. Person.species
+    # Or from within an instance object
+    # i.e. self.species
+    species: str = "Human"
+
+    # This is the method that gets called automatically when an instance of this class (an object) is created
+    # Named parameters here passed into the object creation are declared with default values
+    def __init__(self, first_name: int = "", last_name: int = "", height: float = 0.0, weight: float = 0.0):
+        # We must create instance variables from the passed parameters
+        # Instance variables are only available within objects of a particular class type
+        self.first_name = first_name
+        self.last_name = last_name
+        self.height = height
+        self.weight = weight
+    
+    # This is a simple method to return a full name as a concatination of first and last names
+    def full_name(self):
+        return self.first_name + " " + self.last_name
+    
+    # __repr__ is a special function called when you (for example) print() an object of this class type
+    # It is meant to be used to generate a human readable and machine parseable representation of this class
+    def __repr__(self):
+        return f"{self.__class__.__name__}(species='{self.species}', first_name='{self.first_name}', last_name='{self.last_name}', height={self.height}, weight={self.weight})"
+
+class Student(Person):
+    def __init__(self, school_name: str = "", id: int = 0):
+        # We first call the parent's __init__ method to include it's attributes and methods here
+        super().__init__()
+        self.school_name = school_name
+        self.id = id
+    
+    def __repr__(self):
+        return f"{self.__class__.__name__}(species='{self.species}', first_name='{self.first_name}', last_name='{self.last_name}', height={self.height}, weight={self.weight}, school_name='{self.school_name}', id={self.id})"
+
+class Employee(Person):
+    def __init__(self, company_name: str = "", id: int = 0, salary: int = 0):
+        super().__init__()
+        self.company_name = company_name
+        self.id = id
+        self.salary = salary
+    
+    def __repr__(self):
+        return f"{self.__class__.__name__}(species='{self.species}', first_name='{self.first_name}', last_name='{self.last_name}', height={self.height}, weight={self.weight}, company_name='{self.company_name}', id={self.id}, salary={self.salary})"
+
+# We create a new student with a high school name and ID,
+# but the attributes from the parent are all set to defaults
+my_student = Student("Beavercreek High School", 99)
+print(my_student)
+# We'll also reference Person's class variable just for giggles
+print(f"my_student is of type {my_student.__class__.__name__} which inherits from {my_student.__class__.__base__.__name__} and is a {Student.species}")
+# We create a new employee with all default values
+my_employee = Employee()
+# We set a bunch of attribute values
+my_employee.species = "Anthropomorphic Duck"
+my_employee.first_name = "Scrooge"
+my_employee.last_name = "McDuck"
+my_employee.height = 48
+my_employee.weight = 75
+my_employee.company_name = "Greed, Inc."
+my_employee.id = 1
+my_employee.salary = 99000000
+# Note that we can call the parent method "full_name()" from the child object
+print(f"{my_employee.full_name()} is a {my_employee.species} describe as", my_employee)