Database and SQLAlchemy
This lesson is to help you build your database for your group passion project and set up a data table to store the log-in information of your users.
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
In order to build your log-in system using the following code, you will need to first download an extension: “sqlite viewer”
"""
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)
Model Definition
- Define columns, initialization, and CRUD methods for users table in sqlite.db
This is the model code, or the actual code that will initialize your data table and assign properties to your columns. This table will store the data users input when building thier log-ins to your site.
""" 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.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
This is for when you start running your flask server. It creates initial data in your database for testing.
"""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
This code allows you to search through your database to find individual users. This can be used to check if the username and password matches what the user inputted in the database.
The first block of code uses SQRAlchemy’s ORM capabilities to filter and retrieve a user based on their UID. The UID serves as the primary key for the ‘users’ table in the database.
The second block of code is focused on user authentication. It first checks if a user matching the given UID exists, then verifies if the password entered matches the stored password for that user.
“sqlite.db” is the name of your file
# SQLAlchemy extracts single user from database matching User ID
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.
This is to allow a user to register an account on your site and make it so that their information goes straight to your data table when they do so.
# Inputs, Try/Except, and SQLAlchemy work together to build a valid database object
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())
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
This allows the computer to read all the data in your data table at once. You could use this function if you needed to print out all your data information, for example. It is also more efficient to upload all your data from the backend to frontend at once versus uploading each user’s information individually, and this function allows you to do that.
# 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()
API/Control Terms
APIs work with methods to GET, POST, PUT, and UPDATE data. Control helps with Requests, Response, and handling JSON. Control is glue layer, thus the term Model-View-Control (or MVC).
- POST APIs interact with CREATE methods in Model.
- GET with READ
- PUT with UPDATE.
- DELETE with DELETE.
During development it is best to work with Model and Control without involving View initially. To support this type of development …
- Become familiar with Postman
- FYI, as an alternative you can become familiar with working with APIs through curl
Resource
Control/API code
Control/API concepts are receiving and API request and returning a response.
- Define API flask objects (api/user.py). Flask contains object that help in API definition.
- Register API objects (main.py). Every Flask object in the project needs to be registered with the “main” objects.
- Create/POST method. Post method contains a lot of checking code, but ultimately it creates a database row in the Model and returns that row to the View.
- Read/GET method. This shows off Object Relational Manager performing a User (class operation) to extract all records from the table and putting them into User objects.
- Define API endpoints. Endpoints are somewhat patterns to be matched. Note, url_prefix at top of file supplies “/api/users” prefix for each pattern. Each pattern when matched invokes the correspond class. Methods are defined in class to correspond to expectations (POST, GET, UPDATE, DELETE).
from flask import Blueprint, request, jsonify
from flask_restful import Api, Resource # used for REST API building
from datetime import datetime
from model.users import User
# blueprint, which is registered to app in main.py
user_api = Blueprint('user_api', __name__,
url_prefix='/api/users')
# API docs https://flask-restful.readthedocs.io/en/latest/api.html#id1
api = Api(user_api)
class UserAPI:
class _Create(Resource):
def post(self):
''' Read data for json body '''
body = request.get_json()
''' Avoid garbage in, error checking '''
# validate name
name = body.get('name')
if name is None or len(name) < 2:
return {'message': f'Name is missing, or is less than 2 characters'}, 210
# validate uid
uid = body.get('uid')
if uid is None or len(uid) < 2:
return {'message': f'User ID is missing, or is less than 2 characters'}, 210
# look for password and dob
password = body.get('password')
dob = body.get('dob')
''' #1: Key code block, setup USER OBJECT '''
uo = User(name=name,
uid=uid)
''' Additional garbage error checking '''
# set password if provided
if password is not None:
uo.set_password(password)
# convert to date type
if dob is not None:
try:
uo.dob = datetime.strptime(dob, '%m-%d-%Y').date()
except:
return {'message': f'Date of birth format error {dob}, must be mm-dd-yyyy'}, 210
''' #2: Key Code block to add user to database '''
# create user in database
user = uo.create()
# success returns json of user
if user:
return jsonify(user.read())
# failure returns error
return {'message': f'Processed {name}, either a format error or User ID {uid} is duplicate'}, 210
class _Read(Resource):
def get(self):
users = User.query.all() # read/extract all users from database
json_ready = [user.read() for user in users] # prepare output in json
return jsonify(json_ready) # jsonify creates Flask response object, more specific to APIs than json.dumps
# building RESTapi endpoint
api.add_resource(_Create, '/create')
api.add_resource(_Read, '/')
Testing APIs
Backend Testing of APIs is best done through Browser for simple GET APIs, but other API methods (POST, UPDATE, DELETE) will require a tool like PostMan.
-
Download Postman. This tool test APIs effectively on localhost and is great aid for debugging.
-
Main.py runtime configuration. This configuration is setup to produce same port and localhost as deployment.
Run locally as you develop Select main.py file in VSCode and press Play button, or press down arrow next to Play button to activate Debug testing. The below dialog will appear in Terminal, though IP address will match you machines.
(base) machine:flask_portfolio user$ cd /Users/user/vscode/flask_portfolio ; /usr/bin/env /Users/user/opt/anaconda3/bin/python /Users/user/.vscode/extensions/ms-python.python-2022.20.2/pythonFiles/lib/python/debugpy/adapter/../../debugpy/launcher 61127 -- /Users/user/vscode/flask_portfolio/main.py
* Serving Flask app "__init__" (lazy loading)
* Environment: production
WARNING: This is a development server. Do not use it in a production deployment.
Use a production WSGI server instead.
* Debug mode: on
* Running on all addresses.
WARNING: This is a development server. Do not use it in a production deployment.
* Running on http://192.168.1.75:8086/ (Press CTRL+C to quit)
* Restarting with watchdog (fsevents)
* Debugger is active!
* Debugger PIN: 403-552-045
Test API GET locally with Postman. Observe that tests may be saved.
Test API POST locally with Postman. In this case, Postman can be used to add new records to the table. Observe options to pass data using Body raw-json.
Frontend code
const apiUrl = 'http://localhost:8911/api/Login/'; // Replace with the actual API URL
// Make an HTTP GET request to the API
fetch(apiUrl)
.then(response => response.json()) // Parse the JSON response
.then(data => {
// Organize the data into a dictionary
const organizedData = {
Login_api: {
url_prefix: '/api/Login',
LoginAPI: {
get: {
description: 'Retrieve all Logins from the database',
url: '/api/Login',
method: 'GET',
data: data, // Include the retrieved data here
mode: "cors"
},
},
},
LoginListAPI: {
LoginListAPI: {
get: {
description: 'Retrieve all Logins from the database',
url: '/api/Login',
method: 'GET',
data: data, // Include the retrieved data here
mode: "cors"
},
},
},
};
// Now, you have the organized data in the "organizedData" dictionary
Data = organizedData.Login_api.LoginAPI.get.data; //data[id].Login_name, image whatever u may need,
Errors
Not having SQLite
Windows : sudo apt -get install sqlite 3
Mac cope harder
Python intepreter
Windows and mac:
in vscode, ctrl/command shift p
python; select interpreter
make sure its which python
if you have jwt module vs python (py JWT)
uninstall and reinstall py jwt
FOR ERRORS, try pip install -r requirements.txt