Records contain a number of attributes.

An object contains attributes, and functions (called methods) to get or set these attributes.

UML Diagram for Example

Computer has a fixed ID and type. It has an operating system that can be updated.
Phone is a subclass type of computer, with an additional attribute and methods.

Computer        <-----   Phone
----------               ----------
- id : string;           - operator : string;
- type : string;         ----------
- os: string;            + getOperator()
----------               + changeOperator()
+ getID()
+ getType()
+ getOS()
+ updateOS()

Python Classes#define a new class
class Computer():
    # constructor method with parameters
    def __init__(self, id, type, os):
        #assign parameter values to object attributes
        self.id = id
        self.type = type
        self.os = os
         
        #initial attributes can be manipulated
        self.id = self.id.upper()
 
        # some attributes have default values
        self.previousOS = []
         
    #str method provides formatted output for print commands
    def __str__(self):
        str  = f"ID: {self.id:15} "
        str += f"Type: {self.type:10} "
        str += f"OS: {self.os}"
        str += f"\nPrevious OS: {self.previousOS}"
        return str
     
    # methods to get values of attributes (getters)
    def getID(self):
        return self.id
     
    def getType(self):
        return self.type
     
    def getOS(self):
        return self.os
     
    def getPreviousOS(self):
        return self.previousOS
     
    # methods to update attributes (setters)
    def updateOS(self, newOS):
        self.previousOS.append(self.os)
        self.os = newOS
         
# MAIN PROGRAM   
# instantiation of an object of the class 
computer1 = Computer("AHS1913013","Desktop","Windows Vista")
print(computer1)
 
#use a setter method
computer1.updateOS("Windows 10 Professional")
print(computer1)
 
#use getter methods
id = computer1.getID()
type = computer1.getType()
print(f"Computer {id} is {type}")

Python Classes
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54	`#define a new class` `class` `Computer():` `# constructor method with parameters` `def` `__init__(self,` `id,` `type, os):` `#assign parameter values to object attributes` `self.id` `=` `id` `self.type` `=` `type` `self.os` `=` `os` `#initial attributes can be manipulated` `self.id` `=` `self.id.upper()` `# some attributes have default values` `self.previousOS` `=` `[]` `#str method provides formatted output for print commands` `def` `__str__(self):` `str` `=` `f"ID: {self.id:15} "` `str` `+=` `f"Type: {self.type:10} "` `str` `+=` `f"OS: {self.os}"` `str` `+=` `f"\nPrevious OS: {self.previousOS}"` `return` `str` `# methods to get values of attributes (getters)` `def` `getID(self):` `return` `self.id` `def` `getType(self):` `return` `self.type` `def` `getOS(self):` `return` `self.os` `def` `getPreviousOS(self):` `return` `self.previousOS` `# methods to update attributes (setters)` `def` `updateOS(self, newOS):` `self.previousOS.append(self.os)` `self.os` `=` `newOS` `# MAIN PROGRAM` `# instantiation of an object of the class` `computer1` `=` `Computer("AHS1913013","Desktop","Windows Vista")` `print(computer1)` `#use a setter method` `computer1.updateOS("Windows 10 Professional")` `print(computer1)` `#use getter methods` `id` `=` `computer1.getID()` `type` `=` `computer1.getType()` `print(f"Computer {id} is {type}")`

ID: AHS1913013      Type: Desktop    OS: Windows Vista
Previous OS: []
 
ID: AHS1913013      Type: Desktop    OS: Windows 10 Professional
Previous OS: ['Windows Vista']
  
Computer AHS1913013 is Desktop

Python Subclasses# new class Phone is a subclass of Computer
class Phone(Computer):
    # polymorphism 1
    def __init__(self, id, os, operator):
        # call superclass contructor
        super().__init__(id, "Phone", os)
        # add subclass specific attributes
        self.operator = operator
     
    # polymorphism 2
    # used instead of superclass' method
    def __str__(self):
        str  = f"ID: {self.id:15} "
        str += f"Type: {self.type:10} "
        str += f"OS: {self.os:10} "
        str += f"Operator: {self.operator}"
        str += f"\nPrevious OS: {self.previousOS}"
        return str
     
    def getOperator(self):
        return self.operator
     
    def changeOperator(self, newOperator):
        self.operator = newOperator
 
# MAIN PROGRAM
computer1 = Computer("AHS1913013","Desktop","Windows Vista")
print(computer1)
  
phone1 = Phone("XYZ1234567","Android 8","EE")
print(phone1)

Python Subclasses
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31	`# new class Phone is a subclass of Computer` `class` `Phone(Computer):` `# polymorphism 1` `def` `__init__(self,` `id, os, operator):` `# call superclass contructor` `super().__init__(id,` `"Phone", os)` `# add subclass specific attributes` `self.operator` `=` `operator` `# polymorphism 2` `# used instead of superclass' method` `def` `__str__(self):` `str` `=` `f"ID: {self.id:15} "` `str` `+=` `f"Type: {self.type:10} "` `str` `+=` `f"OS: {self.os:10} "` `str` `+=` `f"Operator: {self.operator}"` `str` `+=` `f"\nPrevious OS: {self.previousOS}"` `return` `str` `def` `getOperator(self):` `return` `self.operator` `def` `changeOperator(self, newOperator):` `self.operator` `=` `newOperator` `# MAIN PROGRAM` `computer1` `=` `Computer("AHS1913013","Desktop","Windows Vista")` `print(computer1)` `phone1` `=` `Phone("XYZ1234567","Android 8","EE")` `print(phone1)`

ID: AHS1913013      Type: Desktop    OS: Windows Vista
Previous OS: []
 
ID: XYZ1234567      Type: Phone      OS: Android 8  Operator: EE
Previous OS: []