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, food):
self._name = name # variables with self prefix become part of the object,
self._uid = uid
self.set_password(password)
self._food = food
# 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
@property
def food(self):
return self._food
@food.setter
def food(self, food):
self._food = food
# 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='Tsukasa Suou', uid='kasa', password='helpMe', food='snacks')
u2 = User(name='Leo Tsukinaga', uid='ousama', password='izumiMyLove', food='coffee')
u3 = User(name='Izumi Sena', uid='sena', password='makotoForever', food='shrimp')
u4 = User(name='Arashi Narukami', uid='naruchan', password='arashi', food='chicken karaage')
u5 = User(name='Ritsu Sakuma', uid='kuma', password='maoIsara', food='soda')
# 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, "makotoForever")
# Change user
print("Test 2, change user 3")
u.name = "George Washington"
u.uid = "jm1021"
u.food = "cheese"
u.set_password("washingmachine")
u = tester(users, u.uid, "washingmachine")
# 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
day = 31
month = 12
year = 2004
def born(dob):
born = (int(day), int(month), int(year))
print (born)
def calculate_age(born):
today = date.today()
ageCalc = today.year - born.year - ((today.month, today.day) < (born.month, born.day))
print ("You are", ageCalc, "years old as of", today,".")
dob = date(2004, 12, 31)
# honestly I was kinda too tired to do this because Disneyland in the rain murdered me but it works so I can't really argue
age = calculate_age(dob)
from werkzeug.security import generate_password_hash, check_password_hash
from datetime import date
import json
from datetime import datetime
class User:
def __init__(self, name, uid, password, dob, classOf):
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
@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):
self._dob = dob
@property
def classOf(self):
return self._classOf
@classOf.setter
def classOf(self, classOf):
self._classOf = classOf
def is_classOf(self, classOf):
today = date.today()
return today.year - self._classOf.year - ((today.month, today.day) < (self._classOf.month, self._classOf.day))
# 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
}
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)def __str__(self):
return f'name: "{self._name}", id: "{self._uid}", psw: "{self._password}", dob: "{str(self._dob)}", classoff: "{str(self._classOf)}"'
# 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})'
def set_classOf(self, classOf):
self._classOf = classOf
class DTEncoder(json.JSONEncoder):
def default(self, obj):
# 👇️ if passed in object is datetime object
# convert it to a string
if isinstance(obj, datetime):
return str(obj)
# 👇️ otherwise use the default behavior
return json.JSONEncoder.default(self, obj)
if __name__ == "__main__":
u1 = User(name='Thomas Edison', uid='toby', password='123toby', dob=date(1847, 2, 11), classOf=date(1990, 2, 2))
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")
#users = [u1]
#json.dumps([user.__dict__ for user in users])
#print("JSON string:\n", json_string, "\n")
from werkzeug.security import generate_password_hash, check_password_hash
from datetime import date
import json
from datetime import datetime
class User:
def __init__(self, name, uid, password, dob, favFood, favDrink):
self._name = name # variables with self prefix become part of the object,
self._uid = uid
self.set_password(password)
self._dob = dob
self._favFood = favFood
self._favDrink = favDrink
@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):
self._dob = dob
@property
def favFood(self):
return self._favFood
# a setter function, allows name to be updated after initial object creation
@favFood.setter
def favFood(self, favFood):
self._favFood = favFood
# check if uid parameter matches user id in object, return boolean
def is_favFood(self, favFood):
return self._favFood == favFood
@property
def favDrink(self):
return self._favDrink
# a setter function, allows name to be updated after initial object creation
@favDrink.setter
def favDrink(self, favDrink):
self._favDrink = favDrink
# check if uid parameter matches user id in object, return boolean
def is_favDrink(self, favDrink):
return self._favDrink == favDrink
# 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,
"favFood" : self._favFood,
"favDrink" : self.favDrink
}
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)def __str__(self):
return f'name: "{self._name}", id: "{self._uid}", psw: "{self._password}", dob: "{str(self._dob)}", favFood: "{str(self._favFood)}",favDrink: "{str(self._favDrink)}"'
# 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},favFood={self._favFood},favDrink={self._favDrink})'
def set_favFood(self, favFood):
self._favFood = favFood
class DTEncoder(json.JSONEncoder):
def default(self, obj):
# 👇️ if passed in object is datetime object
# convert it to a string
if isinstance(obj, datetime):
return str(obj)
# 👇️ otherwise use the default behavior
return json.JSONEncoder.default(self, obj)
if __name__ == "__main__":
u1 = User(name='Kaname Tojou', uid='Kana', password='bees', dob=date(2004, 7, 7), favFood='breath mints', favDrink='cola')
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")
#users = [u1]
#json.dumps([user.__dict__ for user in users])
#print("JSON string:\n", json_string, "\n")
print ("Name:", u1.name)
print ("UID:", u1.uid)
print ("Password:", u1._password)
print ("Date of Birth:", u1.dob)
print ("Favorite Food:", u1._favFood)
print ("Favorite Drink:", u1._favDrink)