Twitter example app.

examples/twitter/app.py

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+import datetime
+import operator
+
+from flask import abort
+from flask import flash
+from flask import Flask
+from flask import redirect
+from flask import render_template
+from flask import request
+from flask import session
+from flask import url_for
+from functools import wraps
+from hashlib import md5
+from walrus import *
+
+# Configure our app's settings.
+DEBUG = True
+SECRET_KEY = 'hin6bab8ge25*r=x&+5$0kn=-#log$pt^#@vrqjld!^2ci@g*b'
+
+# Create a flask application - this `app` object will be used to handle
+# inbound requests, routing them to the proper 'view' functions, etc.
+app = Flask(__name__)
+app.config.from_object(__name__)
+
+# Create a walrus database instance - our models will use this database to
+# persist information.
+database = Database()
+
+# Model definitions - the standard "pattern" is to define a base model class
+# that specifies which database to use. Then, any subclasses will automatically
+# use the correct storage.
+class BaseModel(Model):
+    database = database
+    namespace = 'twitter'
+
+# Model classes specify fields declaratively, like django.
+class User(BaseModel):
+    username = TextField(primary_key=True)
+    password = TextField(index=True)
+    email = TextField()
+
+    followers = ZSetField()
+    following = ZSetField()
+
+    def get_followers(self):
+        # Because all users are added to the `followers` sorted-set with the
+        # same score, when retrieved they will be sorted by key (username).
+        return [User.load(username) for username in self.followers]
+
+    def get_following(self):
+        # Because all users are added to the `following` sorted-set with the
+        # same score, when retrieved they will be sorted by key (username).
+        return [User.load(username) for username in self.following]
+
+    def is_following(self, user):
+        # We can use Pythonic operators when working with Walrus containers.
+        return user.username in self.following
+
+    def gravatar_url(self, size=80):
+        return 'http://www.gravatar.com/avatar/%s?d=identicon&s=%d' % \
+            (md5(self.email.strip().lower().encode('utf-8')).hexdigest(), size)
+
+
+# Simple model with a one-to-many relationship: one user has 0..n messages.
+# A user is associated with a message via the `username` field.
+class Message(BaseModel):
+    username = TextField(index=True)
+    content = TextField()
+    timestamp = DateTimeField(default=datetime.datetime.now)
+
+    def get_user(self):
+        return User.load(self.username)
+
+
+# Flask provides a `session` object, which allows us to store information
+# across requests (stored by default in a secure cookie). This function allows
+# us to mark a user as being logged-in by setting some values in the session:
+def auth_user(user):
+    session['logged_in'] = True
+    session['username'] = user.username
+    flash('You are logged in as %s' % (user.username))
+
+# Get the currently logged-in user, or return `None`.
+def get_current_user():
+    if session.get('logged_in'):
+        try:
+            return User.load(session['username'])
+        except KeyError:
+            session.pop('logged_in')
+
+# View decorator which indicates that the requesting user must be authenticated
+# before they can access the wrapped view. The decorator checks the session to
+# see if they're logged in, and if not redirects them to the login view.
+def login_required(f):
+    @wraps(f)
+    def inner(*args, **kwargs):
+        if not session.get('logged_in'):
+            return redirect(url_for('login'))
+        return f(*args, **kwargs)
+    return inner
+
+# Retrieve an object by primary key. If the object does not exist, return a
+# 404 not found.
+def get_object_or_404(model, pk):
+    try:
+        return model.load(pk)
+    except ValueError:
+        abort(404)
+
+# Custom template filter: Flask allows you to define these functions and then
+# they are accessible in the template. This one returns a boolean whether the
+# given user is following another user.
+@app.template_filter('is_following')
+def is_following(from_user, to_user):
+    return from_user.is_following(to_user)
+
+# Views: these are the actual mappings of url to view function.
+@app.route('/')
+def homepage():
+    # Depending on whether the requesting user is logged in or not, show them
+    # either the public timeline or their own private timeline.
+    if session.get('logged_in'):
+        return private_timeline()
+    else:
+        return public_timeline()
+
+@app.route('/private/')
+def private_timeline():
+    # The private timeline is a bit interesting as it shows how to create a
+    # query dynamically. We are taking all the users the current user follows
+    # and basically performing a big set union on message objects. Matching
+    # messages are then sorted newest to oldest.
+    user = get_current_user()
+    if user.following:
+        query = reduce(operator.or_, [
+            Message.username == username
+            for username, _ in user.following
+        ])
+        messages = Message.query(query, order_by=Message.timestamp.desc())
+    else:
+        messages = []
+    return render_template('private_messages.html', message_list=messages)
+
+@app.route('/public/')
+def public_timeline():
+    # Display all messages, newest to oldest.
+    messages = Message.query(order_by=Message.timestamp.desc())
+    return render_template('public_messages.html', message_list=messages)
+
+@app.route('/join/', methods=['GET', 'POST'])
+def join():
+    if request.method == 'POST' and request.form['username']:
+        username = request.form['username']
+        try:
+            User.load(username)
+        except KeyError:
+            user = User.create(
+                username=username,
+                password=md5(request.form['password']).hexdigest(),
+                email=request.form['email'])
+            auth_user(user)
+            return redirect(url_for('homepage'))
+        else:
+            flash('That username is already taken')
+
+    return render_template('join.html')
+
+@app.route('/login/', methods=['GET', 'POST'])
+def login():
+    if request.method == 'POST' and request.form['username']:
+        try:
+            user = User.get(
+                (User.username == request.form['username']) &
+                (User.password == md5(request.form['password']).hexdigest()))
+        except ValueError:
+            flash('The password entered is incorrect')
+        else:
+            auth_user(user)
+            return redirect(url_for('homepage'))
+
+    return render_template('login.html')
+
+@app.route('/logout/')
+def logout():
+    session.pop('logged_in', None)
+    flash('You were logged out')
+    return redirect(url_for('homepage'))
+
+@app.route('/following/')
+@login_required
+def following():
+    # Get the list of user objects the current user is following.
+    user = get_current_user()
+    return render_template('user_following', user_list=user.get_following())
+
+@app.route('/followers/')
+@login_required
+def followers():
+    # Get the list of user objects the current user is followed by.
+    user = get_current_user()
+    return render_template('user_following', user_list=user.get_followers())
+
+@app.route('/users/')
+def user_list():
+    # Display all users ordered by their username.
+    users = User.query(order_by=User.username)
+    return render_template('user_list.html', user_list=users)
+
+@app.route('/users/<username>/')
+def user_detail(username):
+    # Using the "get_object_or_404" shortcut here to get a user with a valid
+    # username or short-circuit and display a 404 if no user exists in the db.
+    user = get_object_or_404(User, username)
+
+    # Get all the users messages ordered newest-first.
+    messages = Message.query(
+        Message.username == user.username,
+        order_by=Message.timestamp.desc())
+    return render_template(
+        'user_detail.html',
+        message_list=messages,
+        user=user)
+
+@app.route('/users/<username>/follow/', methods=['POST'])
+@login_required
+def user_follow(username):
+    current_user = get_current_user()
+    user = get_object_or_404(User, username)
+    current_user.following.add(user.username, 0)
+    user.followers.add(current_user.username, 0)
+
+    flash('You are following %s' % user.username)
+    return redirect(url_for('user_detail', username=user.username))
+
+@app.route('/users/<username>/unfollow/', methods=['POST'])
+@login_required
+def user_unfollow(username):
+    current_user = get_current_user()
+    user = get_object_or_404(User, username)
+    current_user.following.remove(user.username)
+    user.followers.remove(current_user.username)
+
+    flash('You are no longer following %s' % user.username)
+    return redirect(url_for('user_detail', username=user.username))
+
+@app.route('/create/', methods=['GET', 'POST'])
+@login_required
+def create():
+    # Create a new message.
+    user = get_current_user()
+    if request.method == 'POST' and request.form['content']:
+        message = Message.create(
+            username=user.username,
+            content=request.form['content'])
+        flash('Your message has been created')
+        return redirect(url_for('user_detail', username=user.username))
+
+    return render_template('create.html')
+
+@app.context_processor
+def _inject_user():
+    return {'current_user': get_current_user()}
+
+# allow running from the command line
+if __name__ == '__main__':
+    app.run()

examples/twitter/requirements.txt

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+flask
+redis
+walrus

examples/twitter/run_example.py

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+#!/usr/bin/env python
+
+import sys
+sys.path.insert(0, '../..')
+
+from app import app
+app.run()

examples/twitter/static/style.css

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+body            { font-family: sans-serif; background: #eee; }
+a, h1, h2       { color: #377BA8; }
+h1, h2          { font-family: 'Georgia', serif; margin: 0; }
+h1              { border-bottom: 2px solid #eee; }
+h2              { font-size: 1.2em; }
+
+.page           { margin: 2em auto; width: 35em; border: 5px solid #ccc;
+                  padding: 0.8em; background: white; }
+.page ul        { list-style-type: none; }
+.page li        { clear: both; }
+.metanav        { text-align: right; font-size: 0.8em; padding: 0.3em;
+                  margin-bottom: 1em; background: #fafafa; }
+.flash          { background: #CEE5F5; padding: 0.5em;
+                  border: 1px solid #AACBE2; }
+.avatar         { display: block; float: left; margin: 0 10px 0 0; }
+.message-content { min-height: 80px; }

examples/twitter/templates/create.html

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+{% extends "layout.html" %}
+{% block body %}
+  <h2>Create</h2>
+  <form action="{{ url_for('create') }}" method=post>
+    <dl>
+      <dt>Message:</dt>
+      <dd><textarea name="content"></textarea></dd>
+      <dd><input type="submit" value="Create" /></dd>
+    </dl>
+  </form>
+{% endblock %}

examples/twitter/templates/homepage.html

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+{% extends "layout.html" %}
+{% block body %}
+  <h2>Home</h2>
+  <p>Welcome to the site!</p>
+{% endblock %}

examples/twitter/templates/includes/message.html

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+{% set msg_user = message.get_user() %}
+<a class="avatar" href="{{ url_for('user_detail', username=message.username) }}"><img src="{{ msg_user.gravatar_url() }}" /></a>
+<p class="message-content">{{ message.content|urlize }}</p>

examples/twitter/templates/join.html

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+{% extends "layout.html" %}
+{% block body %}
+  <h2>Join</h2>
+  <form action="{{ url_for('join') }}" method="post">
+    <dl>
+      <dt>Username:</dt>
+      <dd><input type="text" name="username"></dd>
+      <dt>Password:</dt>
+      <dd><input type="password" name="password"></dd>
+      <dt>Email:</dt>
+      <dd><input type="text" name="email">
+        <p><small>(used for gravatar)</small></p>
+      </dd>
+      <dd><input type="submit" value="Join">
+    </dl>
+  </form>
+{% endblock %}

examples/twitter/templates/layout.html

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+<!doctype html>
+<title>Twalrus</title>
+<link rel=stylesheet type=text/css href="{{ url_for('static', filename='style.css') }}">
+<div class=page>
+  <h1><a href="{{ url_for('homepage') }}">Twalrus</a></h1>
+  <div class=metanav>
+  {% if not session.logged_in %}
+    <a href="{{ url_for('login') }}">log in</a>
+    <a href="{{ url_for('join') }}">join</a>
+  {% else %}
+    <a href="{{ url_for('public_timeline') }}">public timeline</a>
+    <a href="{{ url_for('create') }}">create</a>
+    <a href="{{ url_for('logout') }}">log out</a>
+  {% endif %}
+  </div>
+  {% for message in get_flashed_messages() %}
+    <div class=flash>{{ message }}</div>
+  {% endfor %}
+  {% block body %}{% endblock %}
+</div>

examples/twitter/templates/login.html

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+{% extends "layout.html" %}
+{% block body %}
+  <h2>Login</h2>
+  {% if error %}<p class=error><strong>Error:</strong> {{ error }}{% endif %}
+  <form action="{{ url_for('login') }}" method=post>
+    <dl>
+      <dt>Username:
+      <dd><input type=text name=username>
+      <dt>Password:
+      <dd><input type=password name=password>
+      <dd><input type=submit value=Login>
+    </dl>
+  </form>
+{% endblock %}

examples/twitter/templates/private_messages.html

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+{% extends "layout.html" %}
+{% block body %}
+  <h2>Private Timeline</h2>
+  <ul>
+    {% for message in message_list %}
+      <li>{% include "includes/message.html" %}</li>
+    {% endfor %}
+  </ul>
+{% endblock %}

examples/twitter/templates/public_messages.html

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+{% extends "layout.html" %}
+{% block body %}
+  <h2>Public Timeline</h2>
+  <ul>
+    {% for message in message_list %}
+      <li>{% include "includes/message.html" %}</li>
+    {% endfor %}
+  </ul>
+{% endblock %}