Model and Object-Oriented Programming Notes & Hacks
- Vocab
- A Class
- Dot Notation
- Class and Object Code; How to Create Objects and Print Them
- Hacks
- CPT Connection
Vocab
- Class = a blueprint for creating an object (person)
-
Object = a data structure; used like Python variables
- when we have an object, we have specific properties with which can describe the object
- an instance of the class/template
- many objects can be created from the same class
- each object contains its own instance data
- instance data is set up by the constructor ("init" method; init helps us make the object)
- use
self.()to refer to something that's a part/attribute of our object
A Class
- has attributes, which are collections of data
- has methods, which are a collection of functions/procedures
- we use special symbols in our class to help us do stuff with our objects
Dot Notation
- Methods in the class/template become part of the object
-
Methods can be accessed using dot notation:
object.method()
# 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 # user id / username
self.set_password(password)
# a name getter method, extracts name from object
@property
def name(self):
return self._name # we store the underscore, but it will give us the result without the underscore; instead of getting the object ID back, we get the printed version
# 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') # creates user 1 as an object. this object's properties are name, uid, and password.
u2 = User(name='Nicholas Tesla', uid='nick', password='123nick') # creates user 2 as another object
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 from database of users
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") # using function created above to set their password
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 cell in 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, 14)
age = calculate_age(dob)
print(age)
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): # also add classOf up here
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 # adding classOf attribute to define year of graduation
@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
# 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))
@property
def classOf(self):
return self._classOf
# add setter function for classOf
@classOf.setter
def classOf(self, classOf):
self._classOf = classOf
# 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,
"class of" : self.classOf # update dictionary by adding 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)
# 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}, class of={self._classOf})' # update by adding classOf
if __name__ == "__main__":
u1 = User(name='Thomas Edison', uid='toby', password='123toby', dob=date(1847, 2, 11), classOf='1872')
u2 = User(name='Shreya Sapkal', uid="rev", password='password', dob=date(2001, 1, 1), classOf='2023') # set new user, which is me
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")
print("JSON ready string:\n", u2, "\n") # call new user data
print("Raw Variables of object:\n", vars(u2), "\n")
print("Raw Attributes and Methods of object:\n", dir(u2), "\n")
print("Representation to Re-Create the object:\n", repr(u2), "\n")
from werkzeug.security import generate_password_hash, check_password_hash
from datetime import date
import json
class User:
def __init__(self, name, uid, password, carType):
self._name = name # variables with self prefix become part of the object,
self._uid = uid
self.set_password(password)
self._carType = carType # will store what car type a person chooses (gas vs. electric) so we can show it as stats for site visitors
@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 carType(self):
return self._carType
# a setter function, allows classOf to be updated after initial object creation
@carType.setter
def name(self, carType):
self._carType = carType
# dictionary is customized, removing password for security purposes
@property
def dictionary(self):
dict = {
"name" : self.name,
"uid" : self.uid,
"selected car type" : self.carType
}
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}, selected car type={self._carType})'
if __name__ == "__main__":
u1 = User(name='Thomas Edison', uid='toby', password='123toby', carType='electric')
u2 = User(name='Shreya Sapkal', uid='rev', password='password', carType='gasoline')
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")
print("JSON ready string:\n", u2, "\n")
print("Raw Variables of object:\n", vars(u2), "\n")
print("Raw Attributes and Methods of object:\n", dir(u2), "\n")
print("Representation to Re-Create the object:\n", repr(u2), "\n")
- something I want to add: code segment that counts up how many users chose gasoline for car type and how many chose electric
- way to display comparison of how many users have chosen each type