Model and Object-Oriented Programming
Object Oriented Programming is a part of learning Python. The objective of this blog is to introduce OOP with the intention of PBL task to create a database. The foundations for a database is defining a Class and understanding instance data and methods. A database is often a focus of backend coding as it will store persistent data, that can be recalled after the immediate session is closed.
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 ...)
# 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)
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 cellin this notebook- Define init and self attributes
- Define setters and getters
- Make a tester
from datetime import date
def calculate_age(born):
today = date.today()
return today.year - born.year - ((today.month, today.day) < (born.month, born.day))
dob = date(2004, 12, 31)
age = calculate_age(dob)
print(age)
class Student:
def __init__(self, name, age, year, date_of_birth):
self.name = name
self.age = age
self.class_of = year
self.date_of_birth = date_of_birth
@property
def get_class_of(self):
return self.class_of
@get_class_of.setter
def set_class_of(self, year):
self.class_of = year
@property
def get_date_of_birth(self):
return self.date_of_birth
@get_date_of_birth.setter
def set_date_of_birth(self, date):
self.date_of_birth = date
# Create a list to store the students
students = []
# Create and add the first student
s = Student("Tanay", 15, 2025, "07-24-2007")
students.append(s)
# Create and add more students
students.append(Student("John", 16, 2026, "01-01-2006"))
students.append(Student("Mary", 17, 2027, "02-14-2005"))
# Print the information for all students
for student in students:
print(student.name)
print(student.age)
print(student.class_of)
print(student.date_of_birth)
import json
class signupInfo:
def __init__(user, firstName, lastName, age, description,):
user._firstName = firstName # variables with self prefix become part of the object,
user._lastName = lastName
user.age = age
user.description = description
# first name getter
@property
def firstName(user):
return user._firstName
# first name setter
@firstName.setter
def firstName(user, firstName):
user._firstName = firstName
# last name getter
@property
def lastName(user):
return user._lastName
# last name setter
@lastName.setter
def lastName(user, lastName):
user._lastName = lastName
#age getter
@property
def ages(user):
return user._age
#age setter
@ages.setter
def ages(user, age):
user._age = age
#description getter
@property
def descriptions(user):
return user._description
# description setter
@descriptions.setter
def descriptions(user, description):
user._age = description
# output content using str(object) in human readable form, uses getter
def __str__(user):
return f'first name: "{user.firstName}", last name: "{user.lastName}", age: "{user.age}", description: "{user.description}'
# output command to recreate the object, uses attribute directly
def __repr__(user):
return f'Person(first name={user._firstName}, last name={user._lastName}, age={user._age}, description: {user._description}'
# tester method to print users
def tester(user, firstName, lastName, age, description):
result = None
for user in users:
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 = signupInfo(firstName='Yuri', lastName='S', age='16', description='I am a hard worker, I have worked in the fast food industry for 1/2 a year')
u2 = signupInfo(firstName='Tanay', lastName='P', age='15', description='I am looking for a job, I want to start creating passive income')
u3 = signupInfo(firstName='Aniket', lastName='C', age='15', description='I am looking forward to working with Burger Bytes, I am an experienced cook and cashier')
u4 = signupInfo(firstName='Soham', lastName='K', age='15', description='I have worked in the fast food industry for a few years now. I have worked at multiple food chains, but burger bytes is calling for me.')
# put user objects in list for convenience
users = [u1, u2, u3, u4]
print("Users in Database in JSON:\n\n",u1)
print(u2)
print(u3)
print(u4)