Class and Object Terms

The foundations of Object-Oriented Programming is defining a Class

  • In Object-Oriented Programming (OOP), a class is a blueprint for creating an Object. (a data structure). An Object is used like many other Python variables.
  • A Class has ...
    • a collection of data, these are called Attributes and in Python are pre-fixed using the keyword self
    • a collection of Functions/Procedures. These are called *Methods when they exist inside a Class definition.
  • An Object is created from the Class/Template. Characteristics of objects ...
    • an Object is an Instance of the Class/Template
    • there can be many Objects created from the same Class
    • each Object contains its own Instance Data
    • the data is setup by the Constructor, this is the "init" method in a Python class
    • all methods in the Class/Template become part of the Object, methods are accessed using dot notation (object.method())
  • A Python Class allow for the definition of @ decorators, these allow access to instance data without the use of functions ...
    • @property decorator (aka getter). This enables developers to reference/get instance data in a shorthand fashion (object.name versus object.get_name())
    • @name.setter decorator (aka setter). This enables developers to update/set instance data in a shorthand fashion (object.name = "John" versus object.set_name("John"))
    • observe all instance data (self._name, self.email ...) are prefixed with "", this convention allows setters and getters to work with more natural variable name (name, email ...)

Class and Object Code

# Werkzeug is a collection of libraries that can be used to create a WSGI (Web Server Gateway Interface)
# A gateway in necessary as a web server cannot communicate directly with Python.
# In this case, imports are focused on generating hash code to protect passwords.
from werkzeug.security import generate_password_hash, check_password_hash
import json

# Define a User Class/Template
# -- A User represents the data we want to manage
class User:    
    # constructor of a User object, initializes the instance variables within object (self)
    def __init__(self, name, uid, password):
        self._name = name    # variables with self prefix become part of the object, 
        self._uid = uid
        self.set_password(password)

    # a name getter method, extracts name from object
    @property
    def name(self):
        return self._name
    
    # a setter function, allows name to be updated after initial object creation
    @name.setter
    def name(self, name):
        self._name = name
    
    # a getter method, extracts email from object
    @property
    def uid(self):
        return self._uid
    
    # a setter function, allows name to be updated after initial object creation
    @uid.setter
    def uid(self, uid):
        self._uid = uid
        
    # check if uid parameter matches user id in object, return boolean
    def is_uid(self, uid):
        return self._uid == uid
    
    @property
    def password(self):
        return self._password[0:10] + "..." # because of security only show 1st characters

    # update password, this is conventional setter
    def set_password(self, password):
        """Create a hashed password."""
        self._password = generate_password_hash(password, method='sha256')

    # check password parameter versus stored/encrypted password
    def is_password(self, password):
        """Check against hashed password."""
        result = check_password_hash(self._password, password)
        return result
    
    # output content using str(object) in human readable form, uses getter
    def __str__(self):
        return f'name: "{self.name}", id: "{self.uid}", psw: "{self.password}"'

    # output command to recreate the object, uses attribute directly
    def __repr__(self):
        return f'Person(name={self._name}, uid={self._uid}, password={self._password})'


# tester method to print users
def tester(users, uid, psw):
    result = None
    for user in users:
        # test for match in database
        if user.uid == uid and user.is_password(psw):  # check for match
            print("* ", end="")
            result = user
        # print using __str__ method
        print(str(user))
    return result
        

# place tester code inside of special if!  This allows include without tester running
if __name__ == "__main__":

    # define user objects
    u1 = User(name='Thomas Edison', uid='toby', password='123toby')
    u2 = User(name='Nicholas Tesla', uid='nick', password='123nick')
    u3 = User(name='Alexander Graham Bell', uid='lex', password='123lex')
    u4 = User(name='Eli Whitney', uid='eli', password='123eli')
    u5 = User(name='Hedy Lemarr', uid='hedy', password='123hedy')

    # put user objects in list for convenience
    users = [u1, u2, u3, u4, u5]

    # Find user
    print("Test 1, find user 3")
    u = tester(users, u3.uid, "123lex")


    # Change user
    print("Test 2, change user 3")
    u.name = "John Mortensen"
    u.uid = "jm1021"
    u.set_password("123qwerty")
    u = tester(users, u.uid, "123qwerty")


    # Make dictionary
    ''' 
    The __dict__ in Python represents a dictionary or any mapping object that is used to store the attributes of the object. 
    Every object in Python has an attribute that is denoted by __dict__. 
    Use the json.dumps() method to convert the list of Users to a JSON string.
    '''
    print("Test 3, make a dictionary")
    json_string = json.dumps([user.__dict__ for user in users]) 
    print(json_string)

    print("Test 4, make a dictionary")
    json_string = json.dumps([vars(user) for user in users]) 
    print(json_string)
Test 1, find user 3
name: "Thomas Edison", id: "toby", psw: "sha256$ZY9..."
name: "Nicholas Tesla", id: "nick", psw: "sha256$KZC..."
* name: "Alexander Graham Bell", id: "lex", psw: "sha256$2zt..."
name: "Eli Whitney", id: "eli", psw: "sha256$Dwu..."
name: "Hedy Lemarr", id: "hedy", psw: "sha256$joZ..."
Test 2, change user 3
name: "Thomas Edison", id: "toby", psw: "sha256$ZY9..."
name: "Nicholas Tesla", id: "nick", psw: "sha256$KZC..."
* name: "John Mortensen", id: "jm1021", psw: "sha256$D29..."
name: "Eli Whitney", id: "eli", psw: "sha256$Dwu..."
name: "Hedy Lemarr", id: "hedy", psw: "sha256$joZ..."
Test 3, make a dictionary
[{"_name": "Thomas Edison", "_uid": "toby", "_password": "sha256$ZY9gsRDbwPh9EBrt$2e3a3eabea046371654a2c4009eef023c84cd4ab8fa8858961407621b332a24b"}, {"_name": "Nicholas Tesla", "_uid": "nick", "_password": "sha256$KZCJprQoMowyVPl1$3d35c968390d75d67a95ec59509d8f55a329830ce01d7d04768be99167c39ecd"}, {"_name": "John Mortensen", "_uid": "jm1021", "_password": "sha256$D29GI132in0YhRYb$48a8ce19c118d1f5c6a6c34e06d75390035744a0a8b8fb13aef66754a91f3a01"}, {"_name": "Eli Whitney", "_uid": "eli", "_password": "sha256$DwukCfQlo69DgnaZ$f354972abf129a161017fc4c231647535cfa60a7a6480d268a5d84ad8c89e1e1"}, {"_name": "Hedy Lemarr", "_uid": "hedy", "_password": "sha256$joZ5szT7gmxRVJji$51f683735b5e31154b5f656ca73dabf05b1e8f3f95147acfd0ee3b11fd2c2607"}]
Test 4, make a dictionary
[{"_name": "Thomas Edison", "_uid": "toby", "_password": "sha256$ZY9gsRDbwPh9EBrt$2e3a3eabea046371654a2c4009eef023c84cd4ab8fa8858961407621b332a24b"}, {"_name": "Nicholas Tesla", "_uid": "nick", "_password": "sha256$KZCJprQoMowyVPl1$3d35c968390d75d67a95ec59509d8f55a329830ce01d7d04768be99167c39ecd"}, {"_name": "John Mortensen", "_uid": "jm1021", "_password": "sha256$D29GI132in0YhRYb$48a8ce19c118d1f5c6a6c34e06d75390035744a0a8b8fb13aef66754a91f3a01"}, {"_name": "Eli Whitney", "_uid": "eli", "_password": "sha256$DwukCfQlo69DgnaZ$f354972abf129a161017fc4c231647535cfa60a7a6480d268a5d84ad8c89e1e1"}, {"_name": "Hedy Lemarr", "_uid": "hedy", "_password": "sha256$joZ5szT7gmxRVJji$51f683735b5e31154b5f656ca73dabf05b1e8f3f95147acfd0ee3b11fd2c2607"}]

Hacks

Add new attributes/variables to the Class. Make class specific to your CPT work.

  • Add classOf attribute to define year of graduation
    • Add setter and getter for classOf
  • Add dob attribute to define date of birth
    • This will require investigation into Python datetime objects as shown in example code below
    • Add setter and getter for dob
  • Add instance variable for age, make sure if dob changes age changes
    • Add getter for age, but don't add/allow setter for age
  • Update and format tester function to work with changes

Start a class design for each of your own Full Stack CPT sections of your project

  • Use new code cell in this notebook
  • Define init and self attributes
  • Define setters and getters
  • Make a tester

Start Code for Hacks

import json
from werkzeug.security import generate_password_hash, check_password_hash
from datetime import datetime
from dateutil.parser import parse

class User:    
    def __init__(self, name, uid, password, classOf, dob, sq):
        self._name = name   
        self._uid = uid
        self.set_password(password)
        self._classOf = classOf
        self._dob = dob
        self._sq = sq
        self._age = self.calculate_age()

    @property
    def name(self):
        return self._name
    
    @name.setter
    def name(self, name):
        self._name = name
    
    @property
    def uid(self):
        return self._uid
    
    @uid.setter
    def uid(self, uid):
        self._uid = uid
        
    def is_uid(self, uid):
        return self._uid == uid
    
    @property
    def password(self):
        return self._password[0:10] + "..." 
    
    def set_password(self, password):
        self._password = generate_password_hash(password, method='sha256')

    def is_password(self, password):
        result = check_password_hash(self._password, password)
        return result
    
    @property
    def classOf(self):
        return self._classOf
    
    @classOf.setter
    def classOf(self, classOf):
        self._classOf = classOf
    
    @property
    def dob(self):
        return self._dob
    
    @dob.setter
    def dob(self, dob):
        self._dob = dob
        self._age = self.calculate_age()

    @property
    def sq(self):
        return self._sq
    
    @sq.setter
    def sq(self, sq):
        self._sq = sq

    @property
    def age(self):
        return self._age
    
    def calculate_age(self):
        today = datetime.now()
        dob = parse(self._dob)
        age = today.year - dob.year - ((today.month, today.day) < (dob.month, dob.day))
        return age
    
    def __str__(self):
        return f'name: "{self.name}", uid: "{self.uid}", classOf: "{self.classOf}", dob: "{self.dob}", sq: "{self.sq}", age: "{self.age}"'

    def __repr__(self):
        return f'User(name={self._name}, uid={self._uid}, classOf={self._classOf}, dob={self._dob}, sq: "{self._sq}", password={self._password})'

def tester(users, uid, psw):
    result = None
    for user in users:
        if user.uid == uid and user.is_password(psw):
            print("* ", end="")
            result = user
        print(str(user))
    return result
        
if __name__ == "__main__":
    u1 = User(name='James Bond', uid='jb', password='123jb', classOf='2023', dob='05/08/2005', sq='What was the name of your childhood imaginary friend and what was their favorite color?')
    u2 = User(name='Ethan Hunt', uid='eh', password='123eh', classOf='2023', dob='05/08/2005', sq='What was the last thing you googled before deciding to create this account?')
    u3 = User(name='John Wick', uid='jw', password='123jw', classOf='2023', dob='05/08/2005', sq='What is the name of the street you grew up on, but backwards and with the first letter capitalized?')
    u4 = User(name='Jason Bourne', uid='jb', password='123jb', classOf='2023', dob='05/08/2005', sq='What was your first pets name and what was the breed?')

    users = [u1, u2, u3, u4]

    print("Find user 3")
    u = tester(users, u3.uid, "123jw")

    print("Update user 3 info")
    u.name = "John Wick"
    u.uid = "jw"
    u.classOf = "2023"
    u.sq = "What is the name of the street you grew up on, but backwards and with the first letter capitalized?"
    u.dob = "05/08/2005"
    u.set_password("123jw")
    u = tester(users, u.uid, "123qwerty")
Find user 3
name: "James Bond", uid: "jb", classOf: "2023", dob: "05/08/2005", sq: "What was the name of your childhood imaginary friend and what was their favorite color?", age: "17"
name: "Ethan Hunt", uid: "eh", classOf: "2023", dob: "05/08/2005", sq: "What was the last thing you googled before deciding to create this account?", age: "17"
* name: "John Wick", uid: "jw", classOf: "2023", dob: "05/08/2005", sq: "What is the name of the street you grew up on, but backwards and with the first letter capitalized?", age: "17"
name: "Jason Bourne", uid: "jb", classOf: "2023", dob: "05/08/2005", sq: "What was your first pets name and what was the breed?", age: "17"
Update user 3 info
name: "James Bond", uid: "jb", classOf: "2023", dob: "05/08/2005", sq: "What was the name of your childhood imaginary friend and what was their favorite color?", age: "17"
name: "Ethan Hunt", uid: "eh", classOf: "2023", dob: "05/08/2005", sq: "What was the last thing you googled before deciding to create this account?", age: "17"
name: "John Wick", uid: "jw", classOf: "2023", dob: "05/08/2005", sq: "What is the name of the street you grew up on, but backwards and with the first letter capitalized?", age: "17"
name: "Jason Bourne", uid: "jb", classOf: "2023", dob: "05/08/2005", sq: "What was your first pets name and what was the breed?", age: "17"