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.
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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"
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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
"""
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)
# makes the sqlite.db file
""" 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 Player(db.Model): # way to inherit the propeties into the user from the template, let the template do database stuff
# template for the properties we want the user to have
__tablename__ = 'football' # 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)
_number = db.Column(db.Integer, unique=False, nullable=False)
_wins = db.Column(db.Integer, unique=False, nullable=False)
_losses = db.Column(db.Integer, unique=False, nullable=False)
# constructor of a User object, initializes the instance variables within object (self)
def __init__(self, name, number, wins, losses): # initialiazes the attributes within the class, uses parameters to be recieved in the init method to instantiate the object of the template user
self._name = name # variables with self prefix become part of the object,
self._number = number
self._wins = wins
self._losses = losses
# a name getter method, extracts name from object
@property # getters let you get the values of the attirbutes in the object
def name(self):
return self._name
# a setter function, allows name to be updated after initial object creation
@name.setter # setter let you change the values of the attirbutes in the object
def name(self, name):
self._name = name
# a getter method, extracts uid from object
@property
def number(self):
return self._number
# a setter function, allows uid to be updated after initial object creation
@number.setter
def number(self, number):
self._number = number
@property
def wins(self):
return self._wins
@wins.setter
def wins(self, wins):
self._wins = wins
@property
def losses(self):
return self._losses
@losses.setter
def losses(self, losses):
self._losses = losses
# 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): # Create lets you make a new data point
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): # lets you retrieve data in the set
return {
"id": self.id,
"name": self.name,
"number": self.number,
"wins": self.wins,
"losses": self.losses,
}
# CRUD update: updates user name, password, phone
# returns self
def update(self, dictionary): # lets you update and change the previous data
for x in dictionary:
if x == "number":
self.number = dictionary[x]
if x == "wins":
self.wins = dictionary[x]
if x == "losses":
self.losses = dictionary[x]
db.session.merge(self)
db.session.commit()
return None
# CRUD delete: remove self
# None
def delete(self): # lets you delete the data or all the data
db.session.delete(self)
db.session.commit()
return None
# makes the class for the user and all of the setters and getters and the crud functions
"""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"""
p1 = Player(name='Patrick Mahomes', number='15', wins='64', losses='16')
p2 = Player(name='JJ Watt', number='99', wins='77', losses='74')
p3 = Player(name='Russell Wilson', number='3', wins='108', losses='64')
p4 = Player(name='Travis Kelce', number='87', wins='105', losses='39')
p5 = Player(name='Joe Burrow', number='9', wins='24', losses='17')
p6 = Player(name='Trevor Lawrence', number='16', wins='12', losses='22')
players = [p1, p2, p3, p4, p5, p6]
"""Builds sample user/note(s) data"""
for x in players:
try:
'''add user to table'''
object = x.create()
print(f"Created new uid {object.name}")
except: # error raised if object nit created
'''fails with bad or duplicate data'''
print(f"Records exist uid {x.name}, or error.")
initUsers()
# adds some tester data to the sqlite.db file
def find_by_name(name):
with app.app_context():
player = Player.query.filter_by(_name=name).first()
return player # 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")
# lets you ind the user by a uid and check if the uid and password correspond with each other
def create():
# optimize user time to see if uid exists
name = input("Enter your name:")
player = find_by_name(name)
try:
print("Found\n", name.read())
return
except:
pass # keep going
# request value that ensure creating valid object
number = input("Enter your number:")
wins = input("Enter your wins:")
losses = input("Enter your losses:")
# Initialize User object before date
player = Player(name=name,
number=number,
wins=wins,
losses=losses
)
# write object to database
with app.app_context():
try:
object = player.create()
print("Created\n", object.read())
except: # error raised if object not created
print("Unknown error name {name}")
create()
# SQLAlchemy extracts all users from database, turns each user into JSON
def read():
with app.app_context():
table = Player.query.all()
json_ready = [player.read() for player in table] # "List Comprehensions", for each user add user.read() to list
return json_ready
read()
def put():
name = str(input("Who do you want to edit?"))
number = int(input("Enter the player's new number or same number"))
wins = int(input("Enter the player's new number of wins"))
losses = int(input("Enter the player's new number of losses"))
body = {
"name": name,
"data": {"number": number, "wins": wins, "losses": losses}
}
data = body.get('data')
player = find_by_name(name)
with app.app_context():
player.update(data)
db.session.commit()
return f"{player.name} at id {player.id} has been updated"
put()
def delete():
name = str(input("Who do you want to delete?"))
player = find_by_name(name)
with app.app_context():
player.delete()
return f"{player.name} at id {player.id} has been deleted"
delete()