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$NZF..."
name: "Nicholas Tesla", id: "nick", psw: "sha256$LLf..."
* name: "Alexander Graham Bell", id: "lex", psw: "sha256$iOB..."
name: "Eli Whitney", id: "eli", psw: "sha256$5W1..."
name: "Hedy Lemarr", id: "hedy", psw: "sha256$Bpx..."
Test 2, change user 3
name: "Thomas Edison", id: "toby", psw: "sha256$NZF..."
name: "Nicholas Tesla", id: "nick", psw: "sha256$LLf..."
* name: "John Mortensen", id: "jm1021", psw: "sha256$pwK..."
name: "Eli Whitney", id: "eli", psw: "sha256$5W1..."
name: "Hedy Lemarr", id: "hedy", psw: "sha256$Bpx..."
Test 3, make a dictionary
[{"_name": "Thomas Edison", "_uid": "toby", "_password": "sha256$NZFZo9MgcZWiswEb$8f2400031d5a74a02a3abe23215554ff6f7b4c7e15a761587e7e7105f9c370e1"}, {"_name": "Nicholas Tesla", "_uid": "nick", "_password": "sha256$LLfWY1czmI0nCvIB$20a8a60bc24991c30038ae9976c66b3764193ade9b2f39561a7dace15bce573b"}, {"_name": "John Mortensen", "_uid": "jm1021", "_password": "sha256$pwKmPHOZSTk5BRmH$17766eb3162740ba01745dbc7a33c2163ddfe6f872089ca461fc11dfd9538882"}, {"_name": "Eli Whitney", "_uid": "eli", "_password": "sha256$5W11yn1jwsPNXkbO$a8f8c882f56d42ced7c33b7ce99c692387f8553013795b082e9f8f7480f1fa67"}, {"_name": "Hedy Lemarr", "_uid": "hedy", "_password": "sha256$BpxCYqFfdLBGPWGg$c6cc58469c7804c67e9ee87330ce273feee2737805348fd3ca51326013e4e710"}]
Test 4, make a dictionary
[{"_name": "Thomas Edison", "_uid": "toby", "_password": "sha256$NZFZo9MgcZWiswEb$8f2400031d5a74a02a3abe23215554ff6f7b4c7e15a761587e7e7105f9c370e1"}, {"_name": "Nicholas Tesla", "_uid": "nick", "_password": "sha256$LLfWY1czmI0nCvIB$20a8a60bc24991c30038ae9976c66b3764193ade9b2f39561a7dace15bce573b"}, {"_name": "John Mortensen", "_uid": "jm1021", "_password": "sha256$pwKmPHOZSTk5BRmH$17766eb3162740ba01745dbc7a33c2163ddfe6f872089ca461fc11dfd9538882"}, {"_name": "Eli Whitney", "_uid": "eli", "_password": "sha256$5W11yn1jwsPNXkbO$a8f8c882f56d42ced7c33b7ce99c692387f8553013795b082e9f8f7480f1fa67"}, {"_name": "Hedy Lemarr", "_uid": "hedy", "_password": "sha256$BpxCYqFfdLBGPWGg$c6cc58469c7804c67e9ee87330ce273feee2737805348fd3ca51326013e4e710"}]

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

from werkzeug.security import generate_password_hash, check_password_hash
from datetime import date
import json

class User:    

    def __init__(self, name, uid, password, dob, classOf, stockNames):
        self._name = name    # variables with self prefix become part of the object, 
        self._uid = uid
        self.set_password(password)
        self._dob = dob
        self._classOf = classOf
        self._stockNames = stockNames
    
    @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
    
    # dob property is returned as string, to avoid unfriendly outcomes
    @property
    def dob(self):
        dob_string = self._dob.strftime('%m-%d-%Y')
        return dob_string
    
    # dob should be have verification for type date
    @dob.setter
    def dob(self, dob):
        if type(dob)== date:
            self._dob = dob
    # Type returns type of an object
    # If type is a date we are changing it

    @property
    def classOf(self):
        return self._classOf

    @classOf.setter
    def classOf(self, classOf):
        self._classOf = classOf

    @property
    def stockNames(self):
        return self._stockNames

    @stockNames.setter
    def stockNames(self, stockNames):
        self._stockNames = stockNames
        
    # age is calculated and returned each time it is accessed
    @property
    def age(self):
        today = date.today()
        return today.year - self._dob.year - ((today.month, today.day) < (self._dob.month, self._dob.day))
    
    # dictionary is customized, removing password for security purposes
    @property
    def dictionary(self):
        dict = {
            "name" : self.name,
            "uid" : self.uid,
            "dob" : self.dob,
            "age" : self.age,
            "classOf" : self.classOf, 
            "stockNames" : self.stockNames
        }
        return dict
    
    # 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 json dumps, this is ready for API response
    def __str__(self):
        return json.dumps(self.dictionary)
    
    # output command to recreate the object, uses attribute directly
    def __repr__(self):
        return f'User(name={self._name}, uid={self._uid}, password={self._password},dob={self._dob},classOf={self.classOf},stockNames={self.stockNames},)'
    
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

if __name__ == "__main__":
    u1 = User(name='Thomas Edison', uid='toby', password='123toby', dob=date(1847, 2, 11), classOf=1865, stockNames=["APPL", "MSFT", "NVDA", "AMZN"],)
    u2 = User(name='Yasha Khoshini', uid='yogs', password='yashakhoshini1000', dob=date(2007, 10, 5), classOf=2025, stockNames=["APPL", "MSFT", "NVDA", "AMZN"],)
    users = [u1, u2]
    tester(users, u2.uid, "yashakhoshini1000")
    print("JSON ready string:\n", u1, "\n") 
    print("Raw Variables of object:\n", vars(u1), "\n") 
    print("Raw Attributes and Methods of object:\n", dir(u1), "\n")
    print("Representation to Re-Create the object:\n", repr(u1), "\n")
{"name": "Thomas Edison", "uid": "toby", "dob": "02-11-1847", "age": 175, "classOf": 1865, "stockNames": ["APPL", "MSFT", "NVDA", "AMZN"]}
* {"name": "Yasha Khoshini", "uid": "yogs", "dob": "10-05-2007", "age": 15, "classOf": 2025, "stockNames": ["APPL", "MSFT", "NVDA", "AMZN"]}
JSON ready string:
 {"name": "Thomas Edison", "uid": "toby", "dob": "02-11-1847", "age": 175, "classOf": 1865, "stockNames": ["APPL", "MSFT", "NVDA", "AMZN"]} 

Raw Variables of object:
 {'_name': 'Thomas Edison', '_uid': 'toby', '_password': 'sha256$oaU1ChCSPEVVGBVK$9cbb9a0281d4c7625509aa346dfc41543939764f1ccab48ac6bb5c6ef331d623', '_dob': datetime.date(1847, 2, 11), '_classOf': 1865, '_stockNames': ['APPL', 'MSFT', 'NVDA', 'AMZN']} 

Raw Attributes and Methods of object:
 ['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', '_classOf', '_dob', '_name', '_password', '_stockNames', '_uid', 'age', 'classOf', 'dictionary', 'dob', 'is_password', 'is_uid', 'name', 'set_password', 'stockNames', 'uid'] 

Representation to Re-Create the object:
 User(name=Thomas Edison, uid=toby, password=sha256$oaU1ChCSPEVVGBVK$9cbb9a0281d4c7625509aa346dfc41543939764f1ccab48ac6bb5c6ef331d623,dob=1847-02-11,classOf=1865,stockNames=['APPL', 'MSFT', 'NVDA', 'AMZN'],)