Flask

lightweight Python web framework

sample

from flask import Flask, render_template
app = Flask(__name__)

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

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

@app.route("/some_internal_api", methods=['POST'])
def do_something():
    print(request.json)

For some reason request.get_json() only works in POST request

routing

route with decorator

from flask import Flask
app = Flask(__name__)

@app.route("/testing", methods=['POST'])
def something():
    # /testing with type = POST will go to this function
    # do something
    print(request.json)

url_for('<function_name>') will return the route leading to that function

e.g. url_for('something') will return '/testing'

can use this with redirect('target_url')

url_for('static', filename='path/to/file')

will be translate to /static/path/to/file

fallback route

@app.errorhandler(404)
def page_not_found(e):
    return render_template('invalid.html')

CORS

To allow request from another origins, use flask_cors. Note that browsers will still block localhost. See https://stackoverflow.com/questions/10883211.

Install flask-cors

pip3 install flask-cors

Apply the Access-Control-Allow-Origin header

from flask import Flask
from flask_cors import CORS

app = Flask(__name__)
CORS(app)

That's all.

ref
Flask-Cors doc

views / templates

Full doc

Put all your views (html files) in /templates

from flask import Flask, render_template
app = Flask(__name__)

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

select another folder for template & static files

By default, template_folder= ./templates and static_folder = ./static. To change them, specify them in Flask().

app = Flask(__name__, template_folder="vue/dist", static_folder="vue/dist/assets")

https://stackoverflow.com/a/55615550/15493213

passing variables

app.py

@app.route("/haha")
def index():
    return render_template('haha.html', data='haha')

haha,html

{{ data }}

if

{% if request.path != '/' %}
<div class="navbar">
  <a href="{{ url_for('index') }}">Dashboard</a>
</div>
{% endif %}

static files

put static files in /static

use url_for to reference it

e.g. you have /static/style.css
to link it, do

 <link rel=stylesheet type=text/css href="{{ url_for('static', filename='style.css') }}">

Relational Database ORM

use SQLAlchemy