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
"""
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:///instance/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)
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
- it is the template of user
- db.Model inheritance
- inheritance is when the model inherites different values / things from the db
-
init method
- the constructor of the object
-
@property,@<column>.setter - create, read, update, delete methods
- CRUD is essential things in every database
- class User
""" 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 User(db.Model):
__tablename__ = 'users' # 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)
_dob = db.Column(db.Date)
# constructor of a User object, initializes the instance variables within object (self)
def __init__(self, name, uid, password="123qwerty", dob=datetime.today()):
self._name = name # variables with self prefix become part of the object,
self._uid = uid
self.set_password(password)
if isinstance(dob, str): # not a date type
dob = date=datetime.today()
self._dob = dob
# 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 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
# dob property is returned as string, a string represents date outside object
@property
def dob(self):
dob_string = self._dob.strftime('%m-%d-%Y')
return dob_string
# dob setter, verifies date type before it is set or default to today
@dob.setter
def dob(self, dob):
if isinstance(dob, str): # not a date type
dob = date=datetime.today()
self._dob = dob
# age is calculated field, age is returned according to date of birth
@property
def age(self):
today = datetime.today()
return today.year - self._dob.year - ((today.month, today.day) < (self._dob.month, self._dob.day))
# 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,
"dob": self.dob,
"age": self.age,
}
# CRUD update: updates user name, password, phone
# returns self
def update(self, name="", uid="", password=""):
"""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)
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
- it is similiar to appending the data in lists. But if there is same data, it is unable to append
- User Object Constructors
- who create the more data
- Try / Except
- try:make an attempt or effort to do something, except: not including; other than
- Create All Tables from db Object
"""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 = User(name='Thomas Edison', uid='toby', password='123toby', dob=datetime(1847, 2, 11))
u2 = User(name='Nikola Tesla', uid='niko', password='123niko')
u3 = User(name='Alexander Graham Bell', uid='lex', password='123lex')
u4 = User(name='Eli Whitney', uid='whit', password='123whit')
u5 = User(name='Indiana Jones', uid='indi', dob=datetime(1920, 10, 21))
u6 = User(name='Marion Ravenwood', uid='raven', dob=datetime(1921, 10, 21))
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()
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
- query is a one kind of library and filter means to filter with the conditions
- user.password
- first, other people cannot see the password due to hash. And to verify the identity
- User.query.filter_by
uid = input()
def find_by_uid(uid):
with app.app_context():
user = User.query.filter_by(_uid=uid).first()
print(user) # returns user object
find_by_uid(uid)
# 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
- make sure that user can find the username and try it and except
- user = User(...) This is the equation, user is equal to User(...)
- user.dob and try/except dob stands for day of birth
- user.create() and try/except create is a similar make
- user.find_by_uid() and try/except
def create():
# optimize user time to see if uid exists
uid = input("Enter your user id:")
user = find_by_uid(uid)
try:
print("Found\n", user.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
user = User(name=name,
uid=uid,
password=password
)
# create user.dob, fail with today as dob
dob = input("Enter your date of birth 'YYYY-MM-DD'")
try:
user.dob = datetime.strptime(dob, '%Y-%m-%d').date()
except ValueError:
user.dob = datetime.today()
print(f"Invalid date {dob} require YYYY-mm-dd, date defaulted to {user.dob}")
# write object to database
with app.app_context():
try:
object = user.create()
print("Created\n", object.read())
db.session.commit()
except: # error raised if object not created
print("Unknown error uid {uid}")
create()
# SQLAlchemy extracts all users from database, turns each user into JSON
def read():
with app.app_context():
table = User.query.all()
json_ready = [user.read() for user in table] # "List Comprehensions", for each user add user.read() to list
return json_ready
read()
def update_user():
uid = input("Enter your user id:")
password = input('Enter your password')
change = input("what do you want to change")
if uid is None:
return {'message': f'User ID is missing'}, 400
if password is None:
return {'message': f'password is missing'}, 400
with app.app_context():
try:
user = User.query.filter_by(_uid=uid).first()
except:
return "so such user"
if change == "uid":
update_content = input("what do you want to change")
user.uid = update_content
user_change = User.query.filter_by(_uid=update_content).first()
db.session.commit()
print(user_change)
if change == "password":
update_content = input("what do you want to change")
user.password = update_content
user_change = User.query.filter_by(_password=update_content).first()
db.session.commit()
print(user_change)
if change == "dob":
update_year = input("Year")
update_month = input("month")
update_day = input("day")
user.dob = datetime(update_year, update_month, update_day)
db.session.commit()
print(user)
update_user()
def delete_user():
uid = input("Enter your user id:")
password = input('Enter your password')
if uid is None:
return {'message': f'User ID is missing'}, 400
if password is None:
return {'message': f'password is missing'}, 400
with app.app_context():
user = User.query.filter_by(_uid=uid).first()
user.delete()
print("Complete delete")
delete_user()
read()
import requests
url = "https://billboard3.p.rapidapi.com/hot-100"
querystring = {"date":"2022-07-07","range":"1-10"}
headers = {
"X-RapidAPI-Key": "56cf0d9c39msh90ab47fd56c02e6p1d2792jsn0f4dfaa46b90",
"X-RapidAPI-Host": "billboard3.p.rapidapi.com"
}
response = requests.request("GET", url, headers=headers, params=querystring)
print(response.text)
songs = response.json()
print(songs[0]['weeksAtNo1'])
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:///instance/songs.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)
from datetime import datetime
import json
from sqlalchemy.exc import IntegrityError
class Song(db.Model):
__tablename__ = 'billboard' # table name is plural, class name is singular
_rank = db.Column(db.Integer, primary_key=True)
_title= db.Column(db.String(255), unique=True, nullable=False)
_artist = db.Column(db.String(255), unique=False, nullable=False)
_lastWeek = db.Column(db.String(255), unique=False, nullable=False)
_peakPosition = db.Column(db.String(255), unique=False, nullable=False)
_weeksOnChart = db.Column(db.String(255), unique=False, nullable=False)
# constructor of a User object, initializes the instance variables within object (self)
def __init__(self, rank, title, artist, lastWeek, peakPosition, weeksOnChart):
self._rank = rank
self._title = title # variables with self prefix become part of the object,
self._artist = artist
self._lastWeek = lastWeek
self._peakPosition = peakPosition
self._weeksOnChart = weeksOnChart
@property
def rank(self):
return self._rank
# a setter function, allows name to be updated after initial object creation
@rank.setter
def rank(self, rank):
self._rank = rank
# a name getter method, extracts name from object
@property
def title(self):
return self._title
# a setter function, allows name to be updated after initial object creation
@title.setter
def title(self, title):
self._title = title
# a getter method, extracts uid from object
@property
def artist(self):
return self._artist
# a setter function, allows uid to be updated after initial object creation
@artist.setter
def artist(self, artist):
self._artist = artist
# check password parameter against stored/encrypted password
# def is_subject(self, subject):
# if subject == "English" | subject == "Math" | subject == "Foreign Language" | subject == "Elective" | subject == "Civics" | subject == "Economies" | subject == "History" | subject == "Science":
# return result
@property
def lastWeek(self):
return self._lastWeek
@lastWeek.setter
def lastWeek(self, lastWeek):
self._lastWeek = lastWeek
@property
def peakPosition(self):
return self._peakPosition
@peakPosition.setter
def peakPosition(self, peakPosition):
self._peakPosition = peakPosition
@property
def weeksOnChart(self):
return self._weeksOnChart
@weeksOnChart.setter
def weeksOnChart(self, weeksOnChart):
self._weeksOnChart = weeksOnChart
# 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 {
"rank": self.rank,
"title": self.title,
"artist": self.artist,
"last week": self.lastWeek,
"peakPosition": self.peakPosition,
"weeksOnChart": self.weeksOnChart
}
# CRUD update: updates user name, password, phone
# returns self
def update(self, title="", artist = "", lastWeek = "", peakPosition = "", weeksOnChart = ""):
"""only updates values with length"""
if len(title) > 0:
self.title = title
if len(artist) > 0:
self.artist = artist
if len(lastWeek) > 0:
self.lastWeek = lastWeek
if len(peakPosition) > 0:
self.peakPosition = peakPosition
if len(weeksOnChart) > 0:
self.weeksOnChart = weeksOnChart
db.session.commit()
return self
# CRUD delete: remove self
# None
def delete(self):
db.session.delete(self)
db.session.commit()
return None
import requests
def initSongs():
with app.app_context():
"""Create database and tables"""
db.create_all()
"""Tester data for table"""
songss = []
url = "https://billboard3.p.rapidapi.com/hot-100"
querystring = {"date":"2022-07-07","range":"1-10"}
headers = {
"X-RapidAPI-Key": "56cf0d9c39msh90ab47fd56c02e6p1d2792jsn0f4dfaa46b90",
"X-RapidAPI-Host": "billboard3.p.rapidapi.com"
}
response = requests.request("GET", url, headers=headers, params=querystring)
songs = response.json()
for i in range(len(songs)):
songss.append(Song(rank = int(songs[i]['rank']), title = songs[i]['title'], artist = songs[i]['artist'], lastWeek=songs[i]['lastWeek'], peakPosition= songs[i]['peakPosition'], weeksOnChart=songs[i]['weeksOnChart']))
for song in songss:
try:
object = song.create()
print(f"Created new uid {object}")
except: # error raised if object nit created
print(f"Records exist or error.")
initSongs()
import pandas as pd
def read_songs():
with app.app_context():
songs = Song.query.all()
json_ready = [song.read() for song in songs]
test_result = pd.DataFrame(json_ready)
print(test_result)
read_songs()
def delete_songs():
title = input("Enter your user id:")
print(title)
if title is None:
return {'message': f'User ID is missing'}, 400
with app.app_context():
user = Song.query.filter_by(_title=title).first()
rank = int(user.rank)
user.delete()
print("Complete delete")
i = 1
while True:
if int(rank + i) > 10:
break
user = Song.query.filter_by(_rank=rank+i).first()
if user is None:
print("not found")
break
rank_number = user.read()['rank']
b = rank_number - 1
user.rank = b
i += 1
db.session.commit()
delete_songs()
with app.app_context():
songs = Song.query.all()
json_ready = [song.read() for song in songs]
print(json_ready)
def update_songs():
title = input("Enter your user id:")
print(title)
if title is None:
return {'message': f'User ID is missing'}, 400
with app.app_context():
user = Song.query.filter_by(_title=title).first()
art = input("please change artist")
if user is None:
print("not found")
user.artist = art
db.session.commit()
user1 = Song.query.filter_by(_title=title).first()
print(user1)
update_songs()