Flask Message Flashing
Good applications and user interfaces are all about feedback. Flask provides a simple way to give feedback to a user with the flashing system. It basically makes it possible to record a message at the end of a request and access it next request and only the next request. This is usually combined with a layout template that does this. Browsers and sometimes web servers enforce a limit on cookie sizes. Flashing messages mean that are too large for session cookies that cause message flashing to fail silently.
Simple Flashing
from flask import Flask, flash, redirect, render_template, \
request, url_for
app = Flask(__name__)
app.secret_key = b'_8#y4L"F4Q8z\n\sec]/'
@app.route('/')
def index():
return render_template('index.html')
@app.route('/login', methods=['GET', 'POST'])
def login():
error = None
if request.method == 'POST':
if request.form['username'] != 'admin' or \
request.form['password'] != 'secret':
error = 'Invalid credentials'
else:
flash('You were successfully logged in')
return redirect(url_for('index'))
return render_template('login.html', error=error)
And here is the flash.html template which does the magic:
<!doctype html>
<title>Message Flashing</title>
{% with messages = get_flashed_messages() %}
{% if messages %}
<ul class=flashes>
{% for message in messages %}
<li>{{ message }}</li>
{% endfor %}
</ul>
{% endif %}
{% endwith %}
{% block body %}{% endblock %}Here is the index.html template which inherits from flash.html:
{% extends "flash.html" %}
{% block body %}
<h1>Overview</h1>
<p>Do you want to <a href="{{ url_for('login') }}">log in?</a>
{% endblock %}And here is the login.html template which also inherits from flash.html:
{% extends "flash.html" %}
{% block body %}
<h1>Login</h1>
{% if error %}
<p class=error><strong>Error:</strong> {{ error }}
{% endif %}
<form method=post>
<dl>
<dt>Username:
<dd><input type=text name=username value="{{
request.form.username }}">
<dt>Password:
<dd><input type=password name=password>
</dl>
<p><input type=submit value=Login>
</form>
{% endblock %}
+91-4446311234
+1-6502652492
+91-7530088009
