Unit 2.4a Using Programs with Data, SQLAlchemy
Using Programs with Data is focused on SQL and database actions. Part A focuses on SQLAlchemy and an OOP programming style,
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.
- Flask app object I see this working on the line where it says 'app = Flask(name)'. Which sets up the flask object
- SQLAlchemy db object I see this on the line where it says 'db= SQLAlchemy()'. The purpose is to create properties in the db.
"""
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:///computers.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)
Model Definition
Define columns, initialization, and CRUD methods for users table in sqlite.db
- Comment on these items in the class, purpose and defintion.
- class User:Creates the template to make an object - db.Model inheritance: Crease the SQLite table and database
- init method: This is the constructer of the object, which allows it to create
-
@property,@<column>.setter: @property helps establish the values, while @colum.setter changes the values inputted. - create, read, update, delete methods: CRUD, in the name, create: adds stuff to the db. read: reads the values in the Database. Update: updates values in the database. Delete: deletes values in the Database.
"""
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:///computers.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)
""" 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 'users' 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 Computers(db.Model):
__tablename__ = 'computers' # 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=True, nullable=False)
_graphics = db.Column(db.String(255), unique=False, nullable=False)
_CPU = db.Column(db.String(255), unique=False, nullable=False)
_price = db.Column(db.Integer, unique=False, nullable=False)
_RAM = db.Column(db.Integer, unique=False, nullable=False)
_storage = db.Column(db.Integer, unique=False, nullable=False)
_OS = db.Column(db.String(255), unique=False, nullable=False)
_brand = db.Column(db.String(255), unique=False, nullable=False)
_year = db.Column(db.Integer, unique=False, nullable=False)
# constructor of a User object, initializes the instance variables within object (self)
def __init__(self, name, graphics, CPU, price, RAM, storage, OS, brand, year):
self._name = name # variables with self prefix become part of the object,
self._graphics = graphics
self._CPU = CPU
self._price = price
self._RAM = RAM
self._storage = storage
self._OS = OS
self._brand = brand
self._year = year
# a name getter method, extracts name from object
@property
def name(self):
return self._name
# a name setter method, sets name in object
@name.setter
def name(self, name):
self._name = name
# a graphics getter method, extracts graphics from object
@property
def graphics(self):
return self._graphics
# a graphics setter method, sets graphics in object
@graphics.setter
def graphics(self, graphics):
self._graphics = graphics
# a CPU getter method, extracts CPU from object
@property
def CPU(self):
return self._CPU
# a CPU setter method, sets CPU in object
@CPU.setter
def CPU(self, CPU):
self._CPU = CPU
# a price getter method, extracts price from object
@property
def price(self):
return self._price
# a price setter method, sets price in object
@price.setter
def price(self, price):
self._price = price
# a RAM getter method, extracts RAM from object
@property
def RAM(self):
return self._RAM
# a RAM setter method, sets RAM in object
@RAM.setter
def RAM(self, RAM):
self._RAM = RAM
# a storage getter method, extracts storage from object
@property
def storage(self):
return self._storage
# a storage setter method, sets storage in object
@storage.setter
def storage(self, storage):
self._storage = storage
# a OS getter method, extracts OS from object
@property
def OS(self):
return self._OS
# a OS setter method, sets OS in object
@OS.setter
def OS(self, OS):
self._OS = OS
# a brand getter method, extracts brand from object
@property
def brand(self):
return self._brand
# a brand setter method, sets brand in object
@brand.setter
def brand(self, brand):
self._brand = brand
# a year getter method, extracts year from object
@property
def year(self):
return self._year
# a year setter method, sets year in object
@year.setter
def year(self, year):
self._year = year
# a method to return a dictionary of the object
def to_dict(self):
return {
"id": self.id,
"name": self.name,
"graphics": self.graphics,
"CPU": self.CPU,
"price": self.price,
"RAM": self.RAM,
"storage": self.storage,
"OS": self.OS,
"brand": self.brand,
"year": self.year,
}
# 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
def check_price(self):
if self.price > 1000:
return True
else:
return False
# CRUD read converts self to dictionary
# returns dictionary
def read(self):
return {
"id": self.id,
"name": self.name,
"graphics": self.graphics,
"CPU": self.CPU,
"price": self.price,
"RAM": self.RAM,
"storage": self.storage,
"OS": self.OS,
"brand": self.brand,
"year": self.year,
}
# CRUD update: updates user name, password, phone
# returns self
def update(self, name, graphics, CPU, price, RAM, storage, OS, brand, year):
"""only updates values with length"""
if len(name) > 0:
self.name = name
if len(graphics) > 0:
self.graphics = graphics
if len(CPU) > 0:
self.CPU = CPU
if price > 0:
self.price = price
if RAM > 0:
self.RAM = RAM
if storage > 0:
self.storage = storage
if len(OS) > 0:
self.OS = OS
if len(brand) > 0:
self.brand = brand
if len(year) > 0:
self.year = year
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:works through db.create_all() 2. User Object Constructors: Goes through the Computer() class with the proper parameters
- Try / Except : Try works by attempting to create each object. If it doesn't work, except takes charge, removes the faulty object, and displays an error message.
"""Database Creation and Testing """
# Builds working data for testing
def initComputers():
with app.app_context():
"""Create database and tables"""
db.create_all()
"""Tester data for table"""
c1 = Computers(name='MacBook Pro', graphics='Intel Iris Plus Graphics 645', CPU='2.3GHz 8-core 9th-generation Intel Core i9 processor, Turbo Boost up to 4.8GHz', price=2799, RAM=32, storage=1024, OS='macOS Catalina', brand='Apple', year='2019')
c2 = Computers(name="Dell XPS 13", graphics="Intel UHD Graphics 620", CPU="2.8GHz 8th Generation Intel Core i7-8565U Processor", price=1299, RAM=16, storage=512, OS="Windows 10 Home", brand="Dell", year="2019")
c3 = Computers(name='Hp Dragonfly', graphics='Intel UHD Graphics', CPU='Intel i3-1215U', price=1039.00, RAM=16, storage=512, OS='Windows 10 Home', brand='Hp', year='2019')
c4 = Computers(name='Gigabyte Aero 15 Oled 4k', graphics='3060', CPU='i7 11 gen', price =1440, RAM = 16, storage =512, OS = 'Windows 10',brand = 'Gigabyte', year = '2020')
c5 = Computers(name='MacBook Air', graphics='Intel UHD', CPU='intel i5', price =1220, RAM = 8, storage =256, OS = 'Mac OS',brand = 'Apple', year = '2020')
c6 = Computers(name='Lenovo Thinkpad X1 Extreme', graphics='Nvidia Quadro P2000', CPU='Intel Core i7-9750H', price =2000, RAM = 16, storage =512, OS = 'Windows 10',brand = 'Lenovo', year = '2020')
c7 = Computers(name="Acer Nitro 5", graphics="Nvidia GeForce RTX 3070ti", CPU="Intel Core i7-12700H", price=3, RAM=32, storage=2048, OS="Windows 11 Home", brand="Acer", year="2022")
Comps = [c1, c2, c3, c4, c5, c6, c7]
"""Builds sample user/note(s) data"""
for Computer in Comps:
try:
'''add user to table'''
object = Computer.create()
print(f"Created new record {Computer.name}")
except: # error raised if object nit created
'''fails with bad or duplicate data'''
print(f"Records exist uid {Computer.name}, or error.")
initComputers()
# SQLAlchemy extracts single user from database matching User ID
def name(name):
with app.app_context():
computer = Computers.query.filter_by(_name=name).first()
return computer # returns user object
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:Filters through the data to find and match the uid in the functions parameters. 2. user.password: Checks to see if there is a cooresponding password to username
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:Finds to see if there is already an existing uid that is the same as the inputted uid. Try stops the code if the same uid already exists. If there is no currently existing inputted uid, except makes the code continue running. 2. user = User(...): Creates the User object.
- user.dob and try/except: user.dob is the inputted dob. Try sets the dob in the following format. Except sets it to today and returns and error message if the date isn't inputted correctly.
- user.create() and try/except: Creates the User object. Try creates the user. Except returns an error message if no object is created.
def create():
# optimize user time to see if uid exists
name = input("Enter the name of your computer:")
graphics = input("Enter the graphics of your computer:")
CPU = input("Enter the CPU of your computer:")
price = input("Enter the price of your computer (integer):")
price = int(price)
RAM = input("Enter the RAM of your computer (integer):")
RAM = int(RAM)
storage = input("Enter the storage of your computer (integer):")
storage = int(storage)
OS = input("Enter the OS of your computer:")
brand = input("Enter the brand of your computer:")
year = input("Enter the year of your computer:")
# Initialize User object before date
comp = Computers(name=name, graphics=graphics, CPU=CPU, price=price, RAM=RAM, storage=storage, OS=OS, brand=brand, year=year)
# write object to database
with app.app_context():
try:
object = comp.create()
print("Created\n", object.read())
except: # error raised if object not created
print("Unknown error occurred, or duplicate data.")
create()
def read():
with app.app_context():
table = Computers.query.all()
json_ready = [computer.read() for computer in table] # "List Comprehensions", for each user add user.read() to list
return json_ready
read()
def delete():
# Gets the ID
DComp = input("Enter the computer id to be deleted:")
with app.app_context():
# Gets the user through the ID
ComputerDelete = Computers.query.get(DComp)
if ComputerDelete:
# Deletes the user according to its ID number
ComputerDelete.delete()
print(f"Computer with id {DComp} deleted")
else:
# Error message if delete fails
print(f"Computer with id {DComp} not found")
delete()
def update():
name = input("Enter the name of your computer:")
graphics = input("Enter the graphics of your computer:")
CPU = input("Enter the CPU of your computer:")
price = int(input("Enter the price of your computer (integer):"))
RAM = int(input("Enter the RAM of your computer (integer):"))
storage = int(input("Enter the storage of your computer (integer):"))
OS = input("Enter the OS of your computer:")
brand = input("Enter the brand of your computer:")
year = input("Enter the year of your computer:")
if len(name) <= 0:
return {"error": "Name is required"}
if len(graphics) <= 0:
return {"error": "Graphics is required"}
if len(CPU) <= 0:
return {"error": "CPU is required"}
if price <= 0:
return {"error": "Price is required"}
if RAM <= 0:
return {"error": "RAM is required"}
if storage <= 0:
return {"error": "Storage is required"}
if len(OS) <= 0:
return {"error": "OS is required"}
if len(brand) <= 0:
return {"error": "Brand is required"}
if len(year) <= 0:
return {"error": "Year is required"}
with app.app_context():
# Gets the user through the ID
ComputerUpdate = Computers.query.filter_by(_name=name).first()
if ComputerUpdate:
ComputerUpdate.update(name=name, graphics=graphics, CPU=CPU, price=price, RAM=RAM, storage=storage, OS=OS, brand=brand, year=year)
print(f"Computer with id {name} updated")
else:
# Error message if delete fails
print(f"Computer with id {name} not found")
update()
def menu():
operation = input("Enter: (C)reate (R)ead (U)pdate or (D)elete")
if operation.lower() == 'c':
create()
elif operation.lower() == 'r':
read()
elif operation.lower() == 'u':
update()
elif operation.lower() == 'd':
delete()
elif len(operation)==0: # Escape Key
return
else:
print("Please enter c, r, u, or d")
menu() # recursion, repeat menu
try:
menu() # start menu
except:
print("Perform Jupyter 'Run All' prior to starting menu")