「Flask」01: Basic, Route, Templates, GET, POST

前陣子用 Flask 實做了一個 LifePlaylist App 這裡簡單紀錄一下基本的東西，以後回頭更快重拾記憶🤧

前陣子實做了 Flask App 紀錄一下基本處理!

< Intro >

"A lightweight Python Web Framework ! " ----> Flask Docs

< Quick start to run a Flask App >

Install:

pip install Flask

Create python file:

touch main.py

Import:

from flask import Flask

Create instance:

app = Flask(__name__)

Route:

@app.route('/')
def index():
    return 'Hi Flask App ! '

Setting only when you run python file directly, then execute `app.run()`:

if __name__ == '__main__':
    app.run()

Now run Flask App:

python main.py

And Flask Default Port:5000: http://127.0.0.1:5000 will run on local.

Hi Flask App !

< Handling Route >

Example:

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@app.route('/')
def xxxxxx():

Basic:

@app.route('/login')
def login():
    return 'This is login page.'

Handling Multiple routes with same function:

@app.route('/index')
@app.route('/')
def home():
    return 'Welcome Home.'

Routing parameters:

@app.route('/<number>')
def number():
    return f'Your route is /{number} .'

< Use Template(Jinja2) >

Import:

from flask import render_template

Create xxx.html:

mkdir templates
touch templates/welcome.html

Change return:

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

Pass parameters：

@app.route("/welcome/<yourname>")
def home(yourname):
    return render_template('welcome.html', yourname=yourname)

welcome.html:

Use {{}}

Basic:

{{ yourname }}

List:

{{ list.0 }}

Dict:

{{ Dict.key }}

If statement:

{% if <xxxx> %}
    Hi, {{ xxxx }}!
{% else %}
    Oops...
{% endif %}

For loop:

{% for item in <xxxx> %}
    <li>{{ item }}</li>
{% endfor %}

Use base template:

## Create base.html

{% extends "base.html" %}

Put own content(child templates):

e.g.: {% block content %}{% endblock %}
e.g.: {% block body %}{% endblock %}
e.g.: {% block custom %}{% endblock %}

< GET, POST >

Import:

from flask import request

Setting route with GET method:

Settting Route:

Remember is "methods" not "method"

**locals() can pass all args.

from flask import Flask, request, render_template

app = Flask(__name__)

@app.route('/',methods=['GET'])
def index():
    q = request.args.get('q')
    q2 = request.args.get('q2')
    return render_template('get.html', **locals())

if __name__ == '__main__':
    app.run()

Remember is "templates" not "template"

templates/get.html

{{ q }}
{{ q2 }}

Run local and enter URL

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http://127.0.0.1:5000/?q=123&q2=456

## Should appear 123 456

Setting route with POST method:

Settting /form Route:

from flask import Flask, request, render_template

app = Flask(__name__)

@app.route("/form")
def form():
    return render_template('form.html')
    
if __name__ == '__main__':
    app.run()

Create form.html

Setting action="{{url_for('submit')}}" for POST route

<!DOCTYPE html>
<html lang="en">
<body>
    <form method="POST" action="{{url_for('submit')}}">
    <input type="text" name="name" placeholder="Name">
    <input type="text" name="email" placeholder="Email">
    <button type="submit">Submit</button>
</body>
</html>

Handle /submit Route:

@app.route("/submit", methods=['POST'])
def submit():
    name = request.values['name']
    email = request.values['email']
    return render_template('submit.html',**locals())

Create submit.html

<!DOCTYPE html>
<html lang="en">
<body>
    {{ name }}
    {{ email }}
</body>
</html>

Run local and enter URL

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http://127.0.0.1:5000/form

## Should appear form, fill out name and email, then submit.
## Should go to `http://127.0.0.1:5000/submit`, and show name and email.

Handle both GET and POST with one route:

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

@app.route("/form", methods=["POST","GET"])
def form():
    if request.method == "POST":
        name = request.form['name']
        email = request.form['email']
        return redirect(url_for('submit',**locals()))
    else:
        return render_template('form.html')

@app.route("/submit", methods=['POST'])
def submit():
    name = request.values['name']
    email = request.values['email']
    return render_template('submit.html',**locals())