skillbuilder

Flask Cheat Sheet

by will

Importing Flask

from flask import Flask

Most Used Import Functions

These are some of the most used import functions by Flask developers:

from flask import Flask, render_template, redirect, url_for, request

Boilerplate Code

This is the basic template or barebone structure of a Flask app:

from flask import Flask app = Flask(__name__) @app.route("/")def hello_world():    return "
Hello, World!
" app.run()

Creating a Route

This is to make different endpoints in our Flask app:

@app.route("/")

Setting Allowed Methods

Used to specify which methods are allowed for a request. Allowing GET and POST requests on an endpoint:

methods = ['GET', 'POST']

Re-run While Coding

This is used to automatically rerun the program when the file is saved:

app.run(debug=True)

Change Host

This is used to change the host:

app.run(host='0.0.0.0')

Change Port

This is used to change the port:

app.run(port=80)

Importing SQLAlchemy

from flask_sqlalchemy import SQLAlchemy

Database URI

This is the database’s address:

app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql://username:password@localhost/db_name'

or

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///test.db'

Initialization

This is used to initialize SQLAlchemy:

db = SQLAlchemy(app)

Creating a Model

Class used to get data from the database and to send data to the database:

class TableName(db.Model):     column_1 = db.Column(db.Integer, primary_key=True)    column_2 = db.Column(db.String(80), nullable=False)    column_3 = db.Column(db.String(12), nullable=False)

Get All Data – all() Method

This is used to get all the data from the database:

data = ClassName.query.filter_by().all()

Filtered Data – first() Method

This is used to get the first dataset from the list returned by the filter_by function. You can get targeted data by this:

data = ClassName.query.filter_by().first()

Send/Add Data to Database

This is used to send/add data to the database:

data_to_send = ClassName(column_1=dataset1, column_2=dataset2, column_3=dataset3) db.session.add(data_to_send) db.session.commit()

Delete Data from the Database

This is used to delete data from the database:

data_to_send = ClassName(column_1=dataset1, column_2=dataset2, column_3=dataset3)db.session.delete(data_to_send)db.session.commit()

Request Method

This is used to know what request is made (GET/POST):

request.method

Render Template

This is used to pass and render an HTML file directly:

render_template("file.html")

Solving FSADeprecationWarning

SQLALCHEMY_TRACK_MODIFICATIONS allows you to disable the modification tracking system using this line:

app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False

Creating Database Files

This is used to create database files:

from yourapplicationname import db db.create_all() exit()

Method to Return Database Items

This is used to return database items:

def __repr__(self) -> str:     return f"{self.item}"

Printing Returned Content from the Method

This is used to print returned database items:

data = ClassNameWithMethod.query.all() print(data)

Flask Documentation

Visit the Flask documentation here.

Flask SQLAlchemy Documentation

Visit the Flask SQLAlchemy documentation here.

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