Database and SQLAlchemy

In this blog we will explore using programs with data, focused on Databases. We will use SQLite Database to learn more about using Programs with Data. Use Debugging through these examples to examine Objects created in Code.

College Board talks about ideas like
- Program Usage. "iterative and interactive way when processing information"
- Managing Data. "classifying data are part of the process in using programs", "data files in a Table"
- Insight "insight and knowledge can be obtained from ... digitally represented information"
- Filter systems. 'tools for finding information and recognizing patterns"
- Application. "the preserve has two databases", "an employee wants to count the number of book"
PBL, Databases, Iterative/OOP
- Iterative. Refers to a sequence of instructions or code being repeated until a specific end result is achieved
- OOP. A computer programming model that organizes software design around data, or objects, rather than functions and logic
- SQL. Structured Query Language, abbreviated as SQL, is a language used in programming, managing, and structuring data

Imports and Flask Objects

Defines and key object creations

Comment on where you have observed these working? Provide a defintion of purpose.
1. Flask app object. In Trimester 1 and 2 we used flask app objects to connect the front and backend.
2. SQLAlchemy db object. This was used to create our databse from the trimester 2 project.

"""
These imports define the key objects
"""

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

"""
These object and definitions are used throughout the Jupyter Notebook.
"""

# Setup of key Flask object (app)
app = Flask(__name__)
# Setup SQLAlchemy object and properties for the database (db)
database = 'sqlite:///sqlite.db'  # path and filename of database
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
app.config['SQLALCHEMY_DATABASE_URI'] = database
app.config['SECRET_KEY'] = 'SECRET_KEY'
db = SQLAlchemy()


# This belongs in place where it runs once per project
db.init_app(app)

Notes

we put a stop at db.init_app(app)
We then ran the debug

""" database dependencies to support sqlite examples """
import datetime
from datetime import datetime
import json

from sqlalchemy.exc import IntegrityError
from werkzeug.security import generate_password_hash, check_password_hash


''' Tutorial: https://www.sqlalchemy.org/library.html#tutorials, try to get into a Python shell and follow along '''

# Define the User class to manage actions in the 'drivers' table
# -- Object Relational Mapping (ORM) is the key concept of SQLAlchemy
# -- a.) db.Model is like an inner layer of the onion in ORM
# -- b.) User represents data we want to store, something that is built on db.Model
# -- c.) SQLAlchemy ORM is layer on top of SQLAlchemy Core, then SQLAlchemy engine, SQL
class Driver(db.Model):
    __tablename__ = 'drivers'  # table name is plural, class name is singular

    # Define the User schema with "vars" from object
    id = db.Column(db.Integer, primary_key=True)
    _name = db.Column(db.String(255), unique=False, nullable=False)
    _uid = db.Column(db.String(255), unique=True, nullable=False)
    _password = db.Column(db.String(255), unique=False, nullable=False)
    _points = db.Column(db.String(255), unique=False, nullable=False)

    # constructor of a User object, initializes the instance variables within object (self)
    def __init__(self, name, uid, points, password="123qwerty"):
        self._name = name    # variables with self prefix become part of the object, 
        self._uid = uid
        self.set_password(password)
        self._points = points

    # 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 uid from object
    @property
    def uid(self):
        return self._uid
    
    # a setter function, allows uid 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 points(self):
        return self._points
    
    # a setter function, allows points to be updated
    @points.setter
    def points(self, points):
        self._points = points
        
    @property
    def password(self):
        return self._password[0:10] + "..." # because of security only show 1st characters
    

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

    # check password parameter against 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) is in human readable form
    # output content using json dumps, this is ready for API response
    def __str__(self):
        return json.dumps(self.read())

    # CRUD create/add a new record to the table
    # returns self or None on error
    def create(self):
        try:
            # creates a person object from User(db.Model) class, passes initializers
            db.session.add(self)  # add prepares to persist person object to Users table
            db.session.commit()  # SqlAlchemy "unit of work pattern" requires a manual commit
            return self
        except IntegrityError:
            db.session.remove()
            return None

    # CRUD read converts self to dictionary
    # returns dictionary
    def read(self):
        return {
            "id": self.id,
            "name": self.name,
            "uid": self.uid,
            "points": self.points

        }

    # CRUD update: updates user name, password, phone
    # returns self
    def update(self, name="", uid="", password="", points=""):
        """only updates values with length"""
        if len(name) > 0:
            self.name = name
        if len(uid) > 0:
            self.uid = uid
        if len(password) > 0:
            self.set_password(password)
        if len(points) > 0:
            self.points = points
        db.session.add(self) # performs update when id exists
        db.session.commit()
        return self

    # CRUD delete: remove self
    # None
    def delete(self):
        db.session.delete(self)
        db.session.commit()
        return None

Created new uid max
Created new uid sergio
Created new uid fernando
Created new uid carlos
Created new uid lewis
Created new uid george

[{'id': 1, 'name': 'Max Verstappen', 'uid': 'max', 'points': '44'},
 {'id': 2, 'name': 'Sergio Perez', 'uid': 'sergio', 'points': '43'},
 {'id': 3, 'name': 'Fernando Alonso', 'uid': 'fernando', 'points': '30'},
 {'id': 4, 'name': 'Carlos Sainz', 'uid': 'carlos', 'points': '20'},
 {'id': 5, 'name': 'Lewis Hamilton', 'uid': 'lewis', 'points': '20'},
 {'id': 6, 'name': 'George Russell', 'uid': 'george', 'points': '18'}]

""" database dependencies to support sqlite examples """
import datetime
from datetime import datetime
import json

from sqlalchemy.exc import IntegrityError
from werkzeug.security import generate_password_hash, check_password_hash


''' Tutorial: https://www.sqlalchemy.org/library.html#tutorials, try to get into a Python shell and follow along '''

# Define the User class to manage actions in the 'drivers' table
# -- Object Relational Mapping (ORM) is the key concept of SQLAlchemy
# -- a.) db.Model is like an inner layer of the onion in ORM
# -- b.) User represents data we want to store, something that is built on db.Model
# -- c.) SQLAlchemy ORM is layer on top of SQLAlchemy Core, then SQLAlchemy engine, SQL
class Driver(db.Model):
    __tablename__ = 'drivers'  # table name is plural, class name is singular

    # Define the User schema with "vars" from object
    id = db.Column(db.Integer, primary_key=True)
    _name = db.Column(db.String(255), unique=False, nullable=False)
    _uid = db.Column(db.String(255), unique=True, nullable=False)
    _password = db.Column(db.String(255), unique=False, nullable=False)
    _points = db.Column(db.String(255), unique=False, nullable=False)

    # constructor of a User object, initializes the instance variables within object (self)
    def __init__(self, name, uid, points, password="123qwerty"):
        self._name = name    # variables with self prefix become part of the object, 
        self._uid = uid
        self.set_password(password)
        self._points = points

    # 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 uid from object
    @property
    def uid(self):
        return self._uid
    
    # a setter function, allows uid 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 points(self):
        return self._points
    
    # a setter function, allows points to be updated
    @points.setter
    def points(self, points):
        self._points = points
        
    @property
    def password(self):
        return self._password[0:10] + "..." # because of security only show 1st characters
    

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

    # check password parameter against 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) is in human readable form
    # output content using json dumps, this is ready for API response
    def __str__(self):
        return json.dumps(self.read())

    # CRUD create/add a new record to the table
    # returns self or None on error
    def create(self):
        try:
            # creates a person object from User(db.Model) class, passes initializers
            db.session.add(self)  # add prepares to persist person object to Users table
            db.session.commit()  # SqlAlchemy "unit of work pattern" requires a manual commit
            return self
        except IntegrityError:
            db.session.remove()
            return None

    # CRUD read converts self to dictionary
    # returns dictionary
    def read(self):
        return {
            "id": self.id,
            "name": self.name,
            "uid": self.uid,
            "points": self.points

        }

    # CRUD update: updates user name, password, phone
    # returns self
    def update(self, name="", uid="", password="", points=""):
        """only updates values with length"""
        if len(name) > 0:
            self.name = name
        if len(uid) > 0:
            self.uid = uid
        if len(password) > 0:
            self.set_password(password)
        if len(points) > 0:
            self.points = points
        db.session.add(self) # performs update when id exists
        db.session.commit()
        return self

    # CRUD delete: remove self
    # None
    def delete(self):
        db.session.delete(self)
        db.session.commit()
        return None

Initial Data

Uses SQLALchemy db.create_all() to initialize rows into sqlite.db

Comment on how these work?

Create All Tables from db Object. This creates the table made in the database, with SQLalchemy
User Object Constructors. Creates the user class that holds the drivers name, points, and password.
Try / Except. This creates the row in the table for the driver and its class.
We made a class user that is a template for the user
This Template is used for the class user
Template for a future object
Class user(db.model) is a inheritance that gives the ability to make a class use database methods and attributes
Add to template database information

Init method allows us to instantiate the users from its class.
The CRUD methods allow it for you to have it easier to update and change the database.
We also have the methods not just the attributes

"""Database Creation and Testing """


# Builds working data for testing
def initUsers():
    with app.app_context():
        """Create database and tables"""
        db.create_all()
        """Tester data for table"""
        u1 = Driver(name='Max Verstappen', uid='max', points='44', password='123toby')
        u2 = Driver(name='Sergio Perez', uid='sergio', points='43', password='123niko')
        u3 = Driver(name='Fernando Alonso', uid='fernando', points='30', password='123lex')
        u4 = Driver(name='Carlos Sainz', uid='carlos', points='20', password='123whit')
        u5 = Driver(name='Lewis Hamilton', uid='lewis', points='20', password='7wdc')
        u6 = Driver(name='George Russell', uid='george', points='18',password='password')


        users = [u1, u2, u3, u4, u5, u6]

        """Builds sample user/note(s) data"""
        for user in users:
            try:
                '''add user to table'''
                object = user.create()
                print(f"Created new uid {object.uid}")
            except:  # error raised if object nit created
                '''fails with bad or duplicate data'''
                print(f"Records exist uid {user.uid}, or error.")
                
initUsers()

Created new uid max
Created new uid sergio
Created new uid fernando
Created new uid carlos
Created new uid lewis
Created new uid george

Check for given Credentials in users table in sqlite.db

Use of ORM Query object and custom methods to identify user to credentials uid and password

Comment on purpose of following

User.query.filter_by:Allows the user to be found by their user ID2. user.password: Checks if the users password is corresponding with the correct user's password.

def find_by_uid(uid):
    with app.app_context():
        user = User.query.filter_by(_uid=uid).first()
    return user # returns user object

# Check credentials by finding user and verify password
def check_credentials(uid, password):
    # query email and return user record
    user = find_by_uid(uid)
    if user == None:
        return False
    if (user.is_password(password)):
        return True
    return False
        
#check_credentials("indi", "123qwerty")

Create a new User in table in Sqlite.db

Uses SQLALchemy and custom user.create() method to add row.

Comment on purpose of following

user.find_by_uid() and try/except:This finds if the user already has an account from their id. 2. user = User(...): This is used in the create account to allow the user to create their account with name and password.
user.dob and try/except: This is used to create/set the dob of the user.
user.create() and try/except: This is used to add a new user to the database.

def create():
    # optimize user time to see if uid exists
    uid = input("Enter your user id:")
    driver = find_by_uid(uid)
    try:
        print("Found\n", driver.read())
        return
    except:
        pass # keep going
    
    # request value that ensure creating valid object
    name = input("Enter your name:")
    password = input("Enter your password")
    
    # Initialize User object before date
    driver = Driver(name=name, 
                uid=uid, 
                points=points,
                password=password
                )
    

           
    # write object to database
    with app.app_context():
        try:
            object = user.create()
            print("Created\n", object.read())
        except:  # error raised if object not created
            print("Unknown error uid {uid}")
        
create()

Reading users table in sqlite.db

Uses SQLALchemy query.all method to read data

Comment on purpose of following
1. User.query.all
2. json_ready assignment, google List Comprehension

# SQLAlchemy extracts all users from database, turns each user into JSON
def read():
    with app.app_context():
        table = Driver.query.all()
    json_ready = [user.read() for user in table] # "List Comprehensions", for each user add user.read() to list
    return json_ready

read()

[{'id': 1, 'name': 'Max Verstappen', 'uid': 'max', 'points': '44'},
 {'id': 2, 'name': 'Sergio Perez', 'uid': 'sergio', 'points': '43'},
 {'id': 3, 'name': 'Fernando Alonso', 'uid': 'fernando', 'points': '30'},
 {'id': 4, 'name': 'Carlos Sainz', 'uid': 'carlos', 'points': '20'},
 {'id': 5, 'name': 'Lewis Hamilton', 'uid': 'lewis', 'points': '20'},
 {'id': 6, 'name': 'George Russell', 'uid': 'george', 'points': '18'}]

Hacks

ImageFour

Add this Blog to you own Blogging site. In the Blog add notes and observations on each code cell.
Change blog to your own database.
Add additional CRUD
- Add Update functionality to this blog.
- Add Delete functionality to this blog.

def delete_by_uid(): # makes a new function called delete_by_uid
    uid = input("Enter uid of user to be deleted.") # prompts the user to enter the uid
    driver = find_by_uid(uid)  # using previous function to locate user by inputted id
    with app.app_context():
        try:
            object = driver.delete() 
            print(f"User with uid --{uid}-- has been deleted. ")
            db = read()
            print(db)
        except:  # error raised if object not found
           (f"No user with uid {uid} was found.")
        
delete_by_uid()

def user_update():
    uid = input("Enter uid of user to be updated") # define variable uid so user inputs
    driver = find_by_uid(uid) # calls the find_by_uid function
    name = input("Enter new name:") # prompts user to enter new name
    password = input("Enter new password:") # prompts user to enter the new password
    points = input("enter points") # User needs to enter new points
    with app.app_context(): 
        try:
            object = driver.update(name=name,uid=uid, points=points, password=password) # change the table data of that user
            print(f"User with uid --{uid}-- has been updated: {object} ") # like console log, tells user it has been updated
        except:  # error raised if object not found
           (f"No user with uid {uid} was found.") # If user inputs a uid that is not there, it will show this
    db = read() # calls the read function
    print("---Updated db:---")
    print(db)
user_update() # calls the user_update function

Unit 2.4a Using Programs with Data, SQLAlchemy

Database and SQLAlchemy

Imports and Flask Objects

Model Definition

Initial Data

Check for given Credentials in users table in sqlite.db

Create a new User in table in Sqlite.db

Reading users table in sqlite.db

Hacks