Flask 基礎知識與實作 part 2¶

Author: 毛毛, Alicia¶

Outline¶

Ch3: Template (part 2)
Ch4: Web Form
Ch5: Email

Ch3: Template (part 2)¶

Link¶

url_for()¶

Generates URLs from the application’s URL map.

url`_`for parameter: `_`external¶

True: return an absolute URL
False: return an relative URL (default)

In [ ]:

url_for("index") # "/"
url_for("index", _external=True) # "http://127.0.0.1:5000/"

Dynamic URLs can be generated by passing the dynamic parts as keyword arguments.¶

In [ ]:

url_for("user", name="maomao", _external=True) # "http://127.0.0.1:5000/user/maomao"

The function will add any extra arguments to the query string.¶

In [ ]:

url_for("index", page=2, _external=True) # "http://127.0.0.1:5000/?page=2"

Modify `<`a href="/"`>` by url_for()¶

In [ ]:

<!-- templates/base.html -->

{% extends "bootstrap/base.html" %}

{% block title %}Flasky{% endblock %}

{% block navbar %}
<div class="navbar navbar-inverse" role="navigation">
    <div class="container">
        <div class="navbar-header">
            <button type="button" class="navbar-toggle"
            data-toggle="collapse" data-target=".navbar-collapse">
                <span class="sr-only">Toggle navigation</span>
                <span class="icon-bar"></span>
                <span class="icon-bar"></span>
                <span class="icon-bar"></span>
            </button>
            <a class="navbar-brand" href="{{ home }}">Flasky</a>
        </div>
        <div class="navbar-collapse collapse">
            <ul class="nav navbar-nav">
                <li><a href="{{ home }}">Home</a></li>
            </ul>
        </div>
    </div>
</div>
{% endblock %}

{% block content %}
<div class="container">
    {% block page_content %}{% endblock %}
</div>
{% endblock %}

In [ ]:

<!-- templates/user.html -->

{% extends "base.html" %}

{% block title %}Flasky - Welcom{% endblock %}

{% block page_content %}
<div class="page-header">
    <h1>Hello, {{ name }}!</h1>
</div>
{% endblock %}

In [ ]:

from flask import url_for

@app.route("/user/<name>")
def user(name):
    home = url_for("index", _external=True)
    return render_template("user.html", name=name, home=home)

Result¶

Problem¶

Each view func needs to provide 'home' variable to render template

Solution¶

url_for() can also be used in template

In [ ]:

<!-- templates/base.html -->

{% extends "bootstrap/base.html" %}

{% block title %}Flasky{% endblock %}

{% block navbar %}
<div class="navbar navbar-inverse" role="navigation">
    <div class="container">
        <div class="navbar-header">
            <button type="button" class="navbar-toggle"
            data-toggle="collapse" data-target=".navbar-collapse">
                <span class="sr-only">Toggle navigation</span>
                <span class="icon-bar"></span>
                <span class="icon-bar"></span>
                <span class="icon-bar"></span>
            </button>
            <a class="navbar-brand" href="{{ url_for('index', _external=True) }}">Flasky</a>
        </div>
        <div class="navbar-collapse collapse">
            <ul class="nav navbar-nav">
                <li><a href="{{ url_for('index', _external=True) }}">Home</a></li>
            </ul>
        </div>
    </div>
</div>
{% endblock %}

{% block content %}
<div class="container">
    {% block page_content %}{% endblock %}
</div>
{% endblock %}

Static files¶

Images, CSS, javascript
References to static files are treated as a special route defined as /static/<filename>
- You can check out the url_map
By default, flask looks for static files in a subdirectory called 'static' located in the application’s root folder.

In [ ]:

<!-- templates/base.html -->

{% extends "bootstrap/base.html" %}

{% block title %}Flasky{% endblock %}
{% block head %}
{{ super() }}
<link rel="shortcut icon" href="{{ url_for('static', filename='favicon.ico') }}" type="image/x-icon">
<link rel="icon" href="{{ url_for('static', filename='favicon.ico') }}" type="image/x-icon">
{% endblock %}

{% block navbar %}
<div class="navbar navbar-inverse" role="navigation">
    <div class="container">
        <div class="navbar-header">
            <button type="button" class="navbar-toggle"
            data-toggle="collapse" data-target=".navbar-collapse">
                <span class="sr-only">Toggle navigation</span>
                <span class="icon-bar"></span>
                <span class="icon-bar"></span>
                <span class="icon-bar"></span>
            </button>
            <a class="navbar-brand" href="{{ url_for('index', _external=True) }}">Flasky</a>
        </div>
        <div class="navbar-collapse collapse">
            <ul class="nav navbar-nav">
                <li><a href="{{ url_for('index', _external=True) }}">Home</a></li>
            </ul>
        </div>
    </div>
</div>
{% endblock %}

{% block content %}
<div class="container">
    {% block page_content %}{% endblock %}
</div>
{% endblock %}

Before¶

After¶

You can get the above code from github¶

$ git clone https://github.com/win911/flask_class.git
- Skip this if you have done it before.
$ git checkout 35d00b

How to change the static folder?¶

static_folder: Default is 'static'

In [5]:

from flask import Flask
app = Flask(__name__, static_folder="my_static")

Flask extension¶

Localization of Dates and Times with Flask-Moment¶

Integrates moment.js into Jinja2 templates

moment.js¶

Client-side open source library written in JavaScript that renders dates and times in the browser.
1. Server sends UTC to browser.
2. Browser converts UTC to local time.

Because users work in different parts of the world, server needs uniform time units.¶

We often use UTC to stardardize the time and date.

Installation¶

pip install flask-moment

Note¶

Flask-Moment depends on jquery.js in addition to moment.js.
- Need to inlcude them both in the HTML document.
Boostrap alreday includes jquery.js, so we only need to include moment.js.

How to render date and time in template¶

We need to pass a date and time variable to the template for rendering.
Flask-Moment provides a moment class varialble to tempaltes for rendering.
format('LLL') determines the rendering style, from 'L' to 'LLLL'.
- L: Month numeral, day of month, year (EX: 08/27/2017)
- LL: Month name, day of month, year (EX: August 27, 2017)
- LLL: Month name, day of month, year, time (EX: August 27, 2017 5:32 PM)
- LLLL: Day of week, month name, day of month, year, time (EX: Sunday, August 27, 2017 5:37 PM)

In [ ]:

<!-- templates/index.html -->

{% extends "base.html" %}

{% block title %}Flasky - Index{% endblock %}
{% block scripts %}
{{ super() }}
{{ moment.include_moment() }}
{% endblock %}

{% block page_content %}
<div class="page-header">
    <p>The local data and time is {{ moment(current_time).format('LLL') }}.</p>
    <p>That was {{ moment(current_time).fromNow(refresh = True) }}</p>
</div>
{% endblock %}

In [ ]:

# hello.py

from datetime import datetime

from flask import Flask, render_template
from flask_bootstrap import Bootstrap
from flask_moment import Moment
#from flask.ext.bootstrap import Bootstrap
#from flask.ext.moment import Moment

app = Flask(__name__)
bootstrap = Bootstrap(app)
moment = Moment(app)

@app.route('/')
def index():
    return render_template('index.html', current_time = datetime.utcnow())

if __name__ == "__main__":
    app.run(debug=True)

First view¶

After two minutes¶

You can get the above code from github¶

$ git clone https://github.com/win911/flask_class.git
- Skip this if you have done it before.
$ git checkout b0bcf5

Ch4: Web Form¶

Receive and process data from the web form¶

Add methods parameter to app.route and tell flask which http methods should be handled.
- GET is the default method.

Use POST to receive data instead of GET for security reasons¶

You can think of GET as a postcard and you can see the content directly.
POST is like a letter with an envelope so you cannot see the content directly.

In [ ]:

# hello.py

from flask import Flask, request

app = Flask(__name__)

@app.route("/", methods=["GET", "POST"]) 
def index():
    if request.method == "POST":
        if request.headers["Content-Type"] == "application/json":
            return "<p>JSON Data: {}</p>".format(request.json)
        elif request.headers["Content-Type"] == "application/x-www-form-urlencoded":
            return "<p>Form Data: {}</p>".format(request.form)

        return "<p>Other Types Data: {}</p>".format(request.data)

    return "<p>Hello</p>"

if __name__ == "__main__":
    app.run(debug=True)

Flask extension¶

WTForms¶

Generate the HTML code for forms.
Validate the submitted form data.

Flask-WTF¶

Wraps WTForms package and provides useful helper functions.
Each web form is represented by a class that inherits from class FlaskForm.
Fields and validators can be imported from WTForms.

Installation¶

pip install flask-wtf

In [ ]:

<!-- tempaltes/index.html -->

{% if name %}
    <p>Hello, {{ name }}!</p>
{% else %}
    <p>Hello, Stranger!</p>
{% endif %}

<form method="POST">
{{ form.hidden_tag() }}    <!-- Important for CSRF token -->
{{ form.name.label }} {{ form.name() }}
{{ form.submit() }}
</form>

In [ ]:

# hello.py

from flask import Flask, render_template
from flask_wtf import FlaskForm
#from flask.ext.wtf import Form
from wtforms import StringField, SubmitField
from wtforms.validators import Required

app = Flask(__name__)
app.config["SECRET_KEY"] = "hard to guess string"    # Important for CSRF token

class NameForm(FlaskForm):
    name = StringField("What is your name?", validators=[Required()]) 
    submit = SubmitField("Submit")

@app.route("/", methods=["GET", "POST"]) 
def index():
    name = None
    form = NameForm()
    if form.validate_on_submit():
        name = form.name.data
        form.name.data = ""
    return render_template("index.html", form=form, name=name)  

if __name__ == "__main__":
    app.run(debug= True)

Display error messages if validation failed¶

In [ ]:

<!-- tempaltes/index.html -->

{% if name %}
    <p>Hello, {{ name }}!</p>
{% else %}
    <p>Hello, Stranger!</p>
{% endif %}

<form method="POST">
{{ form.hidden_tag() }}    <!-- Important for CSRF token -->
{{ form.name.label }} {{ form.name() }}
{{ form.submit() }}
</form>

{% for field in form.errors %}
    <p style="color:red">{{ field }}:</p>
    <ul>
    {% for detail in form.errors[field] %}
        <li style="color:red">{{ detail }}</li>
    {% endfor %}
    </ul>
{% endfor %}

Improve the look of the form¶

Specify id or class attribute and define the css style¶

In [ ]:

<!-- tempaltes/index.html -->

{% if name %}
    <p>Hello, {{ name }}!</p>
{% else %}
    <p>Hello, Stranger!</p>
{% endif %}

<form method="POST">
{{ form.hidden_tag() }}    <!-- Important for CSRF token -->
{{ form.name.label }} {{ form.name(id='my-text-field', class='text-field') }}
{{ form.submit() }}
</form>

{% for field in form.errors %}
    <p style="color:red">{{ field }}:</p>
    <ul>
    {% for detail in form.errors[field] %}
        <li style="color:red">{{ detail }}</li>
    {% endfor %}
    </ul>
{% endfor %}

Use Flask-Bootstrap¶

Generate HTML code.
Display error messages if validation failed.

In [ ]:

<!-- tempaltes/index.html -->

{% if name %}
    <p>Hello, {{ name }}!</p>
{% else %}
    <p>Hello, Stranger!</p>
{% endif %}

{% import "bootstrap/wtf.html" as wtf %}
{{ wtf.quick_form(form) }}

In [ ]:

# hello.py

from flask import Flask, render_template
from flask_bootstrap import Bootstrap
from flask_wtf import FlaskForm
#from flask.ext.wtf import Form
from wtforms import StringField, SubmitField
from wtforms.validators import Required

app = Flask(__name__)
app.config["SECRET_KEY"] = "hard to guess string"    # Important for CSRF token
bootstrap = Bootstrap(app)

class NameForm(FlaskForm):
    name = StringField("What is your name?", validators=[Required()])
    submit = SubmitField("Submit")

@app.route("/", methods=["GET", "POST"])
def index():
    name = None
    form = NameForm()
    if form.validate_on_submit():
        name = form.name.data
        form.name.data = ""
    return render_template("index.html", form=form, name=name)

if __name__ == "__main__":
    app.run(debug=True)

In [ ]:

<!-- tempaltes/index.html -->

{% extends "base.html" %}
{% import "bootstrap/wtf.html" as wtf %}

{% block title %}Flasky{% endblock %}

{% block page_content %}
<div class="page-header">
    <h1>Hello, {% if name %}{{ name }}{% else %}Stranger{% endif %}!</h1>
</div>
{{ wtf.quick_form(form) }}
{% endblock %}

You can get the above code from github¶

$ git clone https://github.com/win911/flask_class.git
- Skip this if you have done it before.
$ git checkout 42a607

Redirects & user sessions¶

When you refresh the page, browsers repeat the last request they have sent¶

When the last request sent is a POST request with form data, you may get a warning from the browsers.

We can solve the problem by using the following way¶

Responding to POST requests with a redirect.
- The browser will issue a GET request for the redirect URL.
- We can store data from previous POST request in 'session' so that the GET request can use it.

By default, user sessions are stored in client-side cookies that are signed using the 'key'.¶

app.config['SECRET_KEY']

In [ ]:

from flask import session, redirect, url_for

@app.route("/", methods=["GET", "POST"]) 
def index():
    form = NameForm()
    if form.validate_on_submit():
        session["name"] = form.name.data
        return redirect(url_for("index"))
    return render_template("index.html", form=form, name=session.get("name"))

Refresh the page before using session and redirection¶

Refresh the page after using session and redirection¶

Message flashing¶

To send confirmation message, warning, or error message to users.

In [ ]:

<!-- tempaltes/index.html -->

{% extends "base.html" %}
{% import "bootstrap/wtf.html" as wtf %}

{% block title %}Flasky{% endblock %}

{% block content %}
<div class="container">
    {% for message in get_flashed_messages() %}
    <div class="alert alert-warning">
        <button type="button" class="close" data-dismiss="alert">&times;</button>
        {{ message }}
    </div>
    {% endfor %}

    {% block page_content %}
    <div class="page-header">
        <h1>Hello, {% if name %}{{ name }}{% else %}Stranger{% endif %}!</h1>
    </div>
    {{ wtf.quick_form(form) }}
    {% endblock %}
</div>
{% endblock %}

In [ ]:

from flask import flash

@app.route("/", methods=["GET", "POST"])
def index():
    form = NameForm()
    if form.validate_on_submit():
        old_name = session.get("name")
        if old_name is not None and old_name != form.name.data:
            flash("Looks like you have changed your name!")
        session["name"] = form.name.data
        return redirect(url_for("index"))
    return render_template("index.html", form=form, name=session.get("name"))

Flashed messages¶

Stored in 'session'.
Removed from 'session' when invoking get_flashed_messages().

You can get the above code from github¶

$ git clone https://github.com/win911/flask_class.git
- Skip this if you have done it before.
$ git checkout 70179d

1. The first time you access this web site¶

GET
- Browser gets session info from response.
- Browser stores session info in cookie.

2. Refresh this web site¶

GET
- Browser sends session info to server by request.

3. Submit "maomao" to server¶

POST
- Server sotres {"name": "maomao"} in session.
- Browser gets new session info from response.
- Browser stores new session info in cookie.
GET
- Browser sends new session info to server by request.

4. Submit "abby" to server¶

POST
- Server sotres {"_flashes": ["Looks like you have changed your name!"], "name": "abby"} in session.
- Browser gets new session info from response.
- Browser stores new session info in cookie.
GET
- Browser sends new session info to server by request.
- Server remove flashed message from session because invoking get_flashed_messages().
- Browser gets new session info from response.
- Browser stores new session info in cookie.

5. Refresh this web site¶

GET
- Browser sends session info to server by request.

Watch out !¶

HTML comment does not work for jinja syntax, it will be still executed.

Ch5: Email¶

Flask extension¶

Email Support with Flask-Mail¶

Wraps smtplib and integrates it with Flask.

Installation¶

$ pip install flask-mail

Flask-mail SMTP server configuration keys¶

Key	Default	Description
MAIL_HOSTNAME	localhost	Hoastname or IP address of teh email server
MAIL_PORT	25	Port of the email server
MAIL_USE_TLS	False	Enable Transport Layer Security (TLS) secruity
MAIL_USE_SSL	False	Enable Secure Sockets layer (SSL) security
MAIL_USERNAME	None	Mail account username
MAIL_PASSWORD	None	Mail account password

[Test] Send email through a Google Gmail account¶

1. Configure the application¶

In [ ]:

# hello_email.py

import os

from flask import Flask
from flask_mail import Mail
#from flask.ext.mail import Mail
from flask_script import Manager

app = Flask(__name__)

app.config['MAIL_SERVER'] = 'smtp.googlemail.com'
app.config['MAIL_PORT'] = 587
app.config['MAIL_USE_TLS'] = True
app.config['MAIL_USERNAME'] = os.environ.get('MAIL_USERNAME')
app.config['MAIL_PASSWORD'] = os.environ.get('MAIL_PASSWORD')
app.config["DEBUG"] = True

mail = Mail(app)
manager = Manager(app)

if __name__ == "__main__":
    manager.run()

2. Add `MAIL_USERNAME` and `MAIL_PASSWORD` to the environment¶

Mac OS X

(venv) $ export MAIL_USERNAME=<Gmail username>
(venv) $ export MAIL_PASSWORD=<Gmail password>

Microsoft Windows

(venv) $ set MAIL_USERNAME=<Gmail username>
(venv) $ set MAIL_PASSWORD=<Gmail password>

3. Send email from Python shell¶

(venv) $ python hello_email.py shell
>>> from flask_mail import Message
>>> from hello_email import mail
>>> msg = Message('test subject', sender='you@example.com', recipients=['you@example.com'])
>>> msg.body = 'text body'
>>> msg.html = '<b>HTML</b> body'
>>> with app.app_context():
...    mail.send(msg)
...

Allow less secure apps¶

Send email again¶

Send email when the username changed¶

Expand `index()` view function to send email¶

Add two template files to create plain text and HTML for the email.
- Store the two template files in a mail subfolder inside templates folder.
Set recipient email to the FLASKY_ADMIN in the environment.
Give user argument to the template for rendering.

Add `FLAKSY_AMDIN` to the environment¶

Mac OS X

(venv) $ export FLASKY_ADMIN=<Gmail username>

Microsoft Windows

(venv) $ set FLASKY_ADMIN=<Gmail username>

templates/mail/new_user.txt¶

In [ ]:

User {{ user }} has joined.

In [ ]:

<!-- templates/mail/new_user.html -->

<p> User <b>{{ user }}</b> has joined. </p>

In [ ]:

# hello.py

import os

from flask import Flask, render_template
from flask import session, redirect, url_for
from flask import flash
from flask_bootstrap import Bootstrap
from flask_mail import Mail, Message
#from flask.ext.mail import Mail, Message
from flask_script import Manager
from flask_wtf import FlaskForm
from wtforms import StringField, SubmitField
from wtforms.validators import Required

app = Flask(__name__)
app.config["SECRET_KEY"] = "hard to guess string"    # Important for CSRF token
app.config['MAIL_SERVER'] = 'smtp.googlemail.com'
app.config['MAIL_PORT'] = 587
app.config['MAIL_USE_TLS'] = True
app.config['MAIL_USERNAME'] = os.environ.get('MAIL_USERNAME')  # do not write information here directly
app.config['MAIL_PASSWORD'] = os.environ.get('MAIL_PASSWORD')  # do not write information here directly
app.config['FLASKY_MAIL_SUBJECT_PREFIX'] = '[Flasky]'
app.config['FLASKY_MAIL_SENDER'] = 'Flasky Admin <your-email@example.com>'
app.config['FLASKY_ADMIN'] = os.environ.get('FLASKY_ADMIN')   # do not write information here directly
app.config['DEBUG'] = True

manager = Manager(app)
bootstrap = Bootstrap(app)
mail = Mail(app)

In [ ]:

class NameForm(FlaskForm):
    name = StringField("What is your name?", validators=[Required()])
    submit = SubmitField("Submit")
    
def send_email(to, subject, template, **kwargs):
    msg = Message(app.config['FLASKY_MAIL_SUBJECT_PREFIX'] + subject,
                  sender=app.config['FLASKY_MAIL_SENDER'], recipients=[to])
    msg.body = render_template(template + '.txt', **kwargs)
    msg.html = render_template(template + '.html', **kwargs)
    mail.send(msg)

@app.route("/", methods=["GET", "POST"])
def index():
    form = NameForm()
    if form.validate_on_submit():
        old_name = session.get("name")
        if old_name is not None and old_name != form.name.data:
            send_email(to=app.config['FLASKY_ADMIN'], subject='New User',
                       template='mail/new_user', user=form.name.data)
        session["name"] = form.name.data
        return redirect(url_for("index"))
    return render_template("index.html", form=form, name=session.get("name"))
    
if __name__ == '__main__':
    manager.run()

Sending Asynchronous Email¶

To aviod unresponsiveness when sending email, we can move the send function to a background thread.

Threading¶

Responsiveness: Move long-running tasks to a worker thread that runs concurrently with the main execution thread for the application to remain responsive to user input while executing tasks in the background.

source: wikipedia

In [ ]:

# hello.py

from threading import Thread

def send_async_email(app, msg):
    with app.app_context():
        mail.send(msg)
        
def send_email(to, subject, template, **kwargs):
    msg = Message(app.config['FLASKY_MAIL_SUBJECT_PREFIX'] + ' ' + subject,
                  sender=app.config['FLASKY_MAIL_SENDER'], recipients=[to])
    msg.body = render_template(template + '.txt', **kwargs)
    msg.html = render_template(template + '.html', **kwargs)
    thr = Thread(target=send_async_email, args=[app, msg])
    thr.start()
    return thr

You can get the above code from github¶

$ git clone https://github.com/win911/flask_class.git
- Skip this if you have done it before.
$ git checkout b95022

Appendix¶

Flask extension¶

Flask-JsonSchema¶

JSON request validation for Flask applications
- Wraps jsonschema package and integrates it with Flask

Installation¶

$ pip install flask-jsonschema

Place schemas in the specified JSONSCHEMA_DIR¶

app.config['JSONSCHEMA_DIR'] = os.path.join(app.root_path, 'schemas')

One schema per file¶

schemas/create_book.json¶

In [ ]:

{
  "type": "object",
  "properties": {
    "title": {"type": "string", "maxLength": 50, "minLength": 10},
    "author": {"type": "string", "maxLength": 30, "minLength": 1}
  },
  "required": ["title", "author"]
}

In [ ]:

# hello_json.py

import os

from flask import Flask, request
from flask_jsonschema import JsonSchema, ValidationError

app = Flask(__name__)
app.config["JSONSCHEMA_DIR"] = os.path.join(app.root_path, "schemas")

jsonschema = JsonSchema(app)

@app.errorhandler(ValidationError)
def on_validation_error(e):
    return "error: {}".format(e)

@app.route("/books", methods=["POST"])
@jsonschema.validate("create_book")
def create_book():
    book_name = request.json["title"]
    return "[success] create book: {}".format(book_name)

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

Multiple schemas per file¶

schemas/books.json¶

In [ ]:

{
  "create": {
    "type": "object",
    "properties": {
      "title": {"type": "string", "maxLength": 50, "minLength": 10},
      "author": {"type": "string", "maxLength": 30, "minLength": 1}
    },
    "required": ["title", "author"]
  },
  "update": {
    "type": "object",
    "properties": {
      "title": {"type": "string", "maxLength": 50, "minLength": 10},
      "author": {"type": "string", "maxLength": 30, "minLength": 1}
    }
  }
}

In [ ]:

# hello_json.py

import os

from flask import Flask, request
from flask_jsonschema import JsonSchema, ValidationError

app = Flask(__name__)
app.config["JSONSCHEMA_DIR"] = os.path.join(app.root_path, "schemas")

jsonschema = JsonSchema(app)

@app.errorhandler(ValidationError)
def on_validation_error(e):
    return "error: {}".format(e)

@app.route("/books", methods=["POST"])
@jsonschema.validate("books", "create")    #
def create_book():
    book_name = request.json["title"]
    return "[success] create book: {}".format(book_name)

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

Validation success¶

Validation fail: 'author' is a required property¶

Validation fail: length of the value of 'title' is too short¶

You can get the above code from github¶

$ git clone https://github.com/win911/flask_class.git
- Skip this if you have done it before.
$ git checkout 276c02

Watch out !¶

flask-jsonschema only validate request.json

Validation fail: request.json is None¶

Use `jsonschema` package to validate both request.form and request.json¶

In [ ]:

# hello_json.py

import os

from flask import Flask, request
from jsonschema import validate, ValidationError

app = Flask(__name__)

schema = {
    "type": "object",
    "properties": {
    "title": {"type": "string", "maxLength": 50, "minLength": 10},
    "author": {"type": "string", "maxLength": 30, "minLength": 1}
    },
    "required": ["title", "author"]
}

@app.errorhandler(ValidationError)
def on_validation_error(e):
    return "error: {}".format(e)

@app.route("/books", methods=["POST"])
def create_book():
    if request.form:
        validate(request.form, schema)
        book_name = request.form["title"]
    elif request.json:
        validate(request.json, schema)
        book_name = request.json["title"]
    else:
        raise ValidationError("Invalid data format")
    return "[success] create book: {}".format(book_name)

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

Validation success: request.form¶

Validation success: request.json¶

Validation fail: invalid data format¶

More information about JSON Schema you can refer to¶

https://spacetelescope.github.io/understanding-json-schema/reference/index.html

You can get the above code from github¶

$ git clone https://github.com/win911/flask_class.git
- Skip this if you have done it before.
$ git checkout 610782

Flask 基礎知識與實作 part 2¶

Author: 毛毛, Alicia¶

Outline¶

Ch3: Template (part 2)¶

Link¶

url_for()¶

url_for parameter: _external¶

Dynamic URLs can be generated by passing the dynamic parts as keyword arguments.¶

The function will add any extra arguments to the query string.¶

Modify <a href="/"> by url_for()¶

Result¶

Problem¶

Solution¶

Static files¶

Before¶

After¶

You can get the above code from github¶

How to change the static folder?¶

Flask extension¶

Localization of Dates and Times with Flask-Moment¶

moment.js¶

Because users work in different parts of the world, server needs uniform time units.¶

Installation¶

Note¶

How to render date and time in template¶

First view¶

After two minutes¶

You can get the above code from github¶

Ch4: Web Form¶

Receive and process data from the web form¶

Use POST to receive data instead of GET for security reasons¶

Flask extension¶

WTForms¶

Flask-WTF¶

Installation¶

Display error messages if validation failed¶

Improve the look of the form¶

Specify id or class attribute and define the css style¶

Use Flask-Bootstrap¶

You can get the above code from github¶

Redirects & user sessions¶

When you refresh the page, browsers repeat the last request they have sent¶

We can solve the problem by using the following way¶

By default, user sessions are stored in client-side cookies that are signed using the 'key'.¶

Introduction to cookie and session¶

Refresh the page before using session and redirection¶

Refresh the page after using session and redirection¶

Message flashing¶

Flashed messages¶

You can get the above code from github¶

Survey the interaction between cookie and session¶

1. The first time you access this web site¶

2. Refresh this web site¶

3. Submit "maomao" to server¶

4. Submit "abby" to server¶

5. Refresh this web site¶

Watch out !¶

Ch5: Email¶

Flask extension¶

Email Support with Flask-Mail¶

Installation¶

Flask-mail SMTP server configuration keys¶

[Test] Send email through a Google Gmail account¶

1. Configure the application¶

2. Add MAIL_USERNAME and MAIL_PASSWORD to the environment¶

3. Send email from Python shell¶

Google may block the sign-in attempt¶

Allow less secure apps¶

Send email again¶

Send email when the username changed¶

Expand index() view function to send email¶

Add FLAKSY_AMDIN to the environment¶

templates/mail/new_user.txt¶

Sending Asynchronous Email¶

Threading¶

You can get the above code from github¶

Appendix¶

Flask extension¶

Flask-JsonSchema¶

Installation¶

url`_`for parameter: `_`external¶

Modify `<`a href="/"`>` by url_for()¶

2. Add `MAIL_USERNAME` and `MAIL_PASSWORD` to the environment¶

Expand `index()` view function to send email¶

Add `FLAKSY_AMDIN` to the environment¶

Use `jsonschema` package to validate both request.form and request.json¶