Setup

App Minimal

from flask import Flask
app = Flask(__name__)

@app.route('/')
def index():
    return 'Hello, World!'

Jalankan App

pip install flask
flask --app app run --debug
# or: python -m flask run --debug

Struktur Proyek

app.py	Titik masuk aplikasi
templates/	Template HTML Jinja2
static/	CSS, JS, gambar
models.py	Model database
requirements.txt	Dependensi Python

Route

Route Dasar

@app.route('/about')
def about():
    return render_template('about.html')

@app.route('/user/')
def profile(username):
    return f'User: {username}'

Variabel URL

<variable>	String (default)
<int:id>	Integer
<float:price>	Float
<path:subpath>	String dengan slash
<uuid:item_id>	UUID

HTTP Method

@app.route('/login', methods=['GET', 'POST'])
def login():
    if request.method == 'POST':
        return do_login()
    return render_template('login.html')

Pembuatan URL

from flask import url_for
url_for('profile', username='alice')
# => '/user/alice'

Template

Render Template

from flask import render_template

@app.route('/posts')
def posts():
    items = get_posts()
    return render_template('posts.html', posts=items)

Sintaks Jinja2

{{ variable }}
{% if user %}Welcome, {{ user.name }}!{% endif %}
{% for item in items %}
  {{ item }}

{% endfor %}

Pewarisan Template

{# base.html #}
{% block content %}{% endblock %}

{# child.html #}
{% extends "base.html" %}
{% block content %}Page{% endblock %}

Filter Umum

\|safe	Render HTML mentah
\|escape	HTML-escape string
\|length	Hitung item
\|default('N/A')	Fallback untuk nilai kosong
\|tojson	Serialisasi ke JSON

Request & Response

Objek Request

from flask import request

request.method          # 'GET', 'POST'
request.args.get('q')   # query string ?q=value
request.form['name']    # form POST data
request.json            # parsed JSON body

Properti Request

request.args	Parameter query string
request.form	Data POST form
request.json	Body JSON yang diparsing
request.files	File yang diunggah
request.headers	Header HTTP
request.cookies	Nilai cookie

Helper Response

from flask import jsonify, redirect, make_response

return jsonify({'status': 'ok'})  # JSON response
return redirect(url_for('index'))  # redirect
resp = make_response('body', 200)
resp.headers['X-Custom'] = 'value'

Session

from flask import session
app.secret_key = 'your-secret-key'
session['user_id'] = 42
uid = session.get('user_id')

Form

Integrasi WTForms

pip install flask-wtf
from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField
from wtforms.validators import DataRequired

Definisi Form

class LoginForm(FlaskForm):
    username = StringField('User', validators=[DataRequired()])
    password = PasswordField('Pass', validators=[DataRequired()])

Gunakan di View

@app.route('/login', methods=['GET', 'POST'])
def login():
    form = LoginForm()
    if form.validate_on_submit():
        user = form.username.data
        return redirect(url_for('dashboard'))
    return render_template('login.html', form=form)

Form di Template

Database

Setup SQLAlchemy

pip install flask-sqlalchemy
from flask_sqlalchemy import SQLAlchemy
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///app.db'
db = SQLAlchemy(app)

Definisi Model

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(80), nullable=False)
    email = db.Column(db.String(120), unique=True)
    posts = db.relationship('Post', backref='author')

Operasi CRUD

user = User(name='Alice', email='[email protected]') db.session.add(user) db.session.commit() User.query.filter_by(name='Alice').first() db.session.delete(user) db.session.commit()

Query Umum

Model.query.all()	Semua record
Model.query.get(id)	Berdasarkan primary key
.filter_by(name='X')	Filter kesetaraan sederhana
.filter(Model.age > 18)	Filter ekspresi
.order_by(Model.name)	Urutkan hasil
.limit(10).offset(20)	Paginasi hasil

Blueprint

Buat Blueprint

from flask import Blueprint
blog = Blueprint('blog', __name__, url_prefix='/blog')

@blog.route('/')
def index():
    return render_template('blog/index.html')

Daftarkan Blueprint

# app.py
from blog import blog
app.register_blueprint(blog)

Pembuatan URL Blueprint

url_for('blog.index')  # => '/blog/'
url_for('blog.post', id=5)  # => '/blog/post/5'

Struktur Blueprint

url_prefix	Prefix semua route dalam blueprint
template_folder	Direktori template kustom
static_folder	File statis khusus blueprint
@bp.before_request	Jalankan sebelum setiap request blueprint

Penanganan Error

Halaman Error Kustom

@app.errorhandler(404)
def not_found(e):
    return render_template('404.html'), 404

@app.errorhandler(500)
def server_error(e):
    return render_template('500.html'), 500

Batalkan Request

from flask import abort

@app.route('/admin')
def admin():
    if not current_user.is_admin:
        abort(403)
    return render_template('admin.html')

Exception Kustom

from werkzeug.exceptions import HTTPException

class InsufficientFunds(HTTPException):
    code = 402
    description = 'Insufficient funds'

Logging

app.logger.info('User %s logged in', username)
app.logger.warning('Disk space low')
app.logger.error('Payment failed: %s', err)

Konfigurasi

Metode Konfigurasi

app.config['DEBUG'] = True
app.config.from_object('config.ProductionConfig')
app.config.from_envvar('APP_SETTINGS')

Pola Config Class

class Config:
    SECRET_KEY = os.environ.get('SECRET_KEY')
    SQLALCHEMY_TRACK_MODIFICATIONS = False

class DevConfig(Config):
    DEBUG = True
    SQLALCHEMY_DATABASE_URI = 'sqlite:///dev.db'

Pengaturan Umum

SECRET_KEY	Kunci signing session (wajib)
DEBUG	Aktifkan mode debug
TESTING	Aktifkan mode test
SQLALCHEMY_DATABASE_URI	String koneksi database
MAX_CONTENT_LENGTH	Ukuran upload maksimum dalam byte
JSON_SORT_KEYS	Urutkan key output JSON

Extension

Extension Populer

Flask-SQLAlchemy	Integrasi ORM
Flask-Migrate	Migrasi database Alembic
Flask-WTF	Penanganan form dengan CSRF
Flask-Login	Manajemen sesi pengguna
Flask-Mail	Pengiriman email
Flask-CORS	Cross-origin resource sharing
Flask-RESTful	Pembuatan REST API
Flask-Caching	Caching response dan fungsi

Flask-Login

from flask_login import LoginManager, login_required
login_manager = LoginManager(app)
login_manager.login_view = 'login'

@login_manager.user_loader
def load_user(user_id):
    return User.query.get(int(user_id))

Flask-Migrate

from flask_migrate import Migrate
migrate = Migrate(app, db)
# flask db init    (once)
# flask db migrate -m "add users"
# flask db upgrade

REFERENSI CEPAT FLASK

Page