Similarities Between Users
When a user visits their own profile, we want to recommend other users whose posts the logged-in user might enjoy reading. To do so, we’ll write a Cypher query that finds users most similar to the logged-in user based on the number of tags they’ve mutually posted about. On the other hand, when the logged-in user visits another user’s profile, we want to display what the two users have in common. For this, we’ll write a Cypher query that finds how many of the logged-in user’s posts the other user has liked, along with which tags they’ve mutually posted about. The /profile/<username> view is defined in views.py:
@app.route('/profile/<username>')
def profile(username):
logged_in_username = session.get('username')
user_being_viewed_username = username
user_being_viewed = User(user_being_viewed_username)
posts = user_being_viewed.get_recent_posts()
similar = []
common = []
if logged_in_username:
logged_in_user = User(logged_in_username)
if logged_in_user.username == user_being_viewed.username:
similar = logged_in_user.get_similar_users()
else:
common = logged_in_user.get_commonality_of_user(user_being_viewed)
return render_template(
'profile.html',
username=username,
posts=posts,
similar=similar,
common=common
)
In models.py:
class User:
...
def get_similar_users(self):
# Find three users who are most similar to the logged-in user
# based on tags they've both blogged about.
query = """
MATCH (you:User)-[:PUBLISHED]->(:Post)<-[:TAGGED]-(tag:Tag),
(they:User)-[:PUBLISHED]->(:Post)<-[:TAGGED]-(tag)
WHERE you.username = {username} AND you <> they
WITH they, COLLECT(DISTINCT tag.name) AS tags
ORDER BY SIZE(tags) DESC LIMIT 3
RETURN they.username AS similar_user, tags
"""
return graph.cypher.execute(query, username=self.username)
def get_commonality_of_user(self, other):
# Find how many of the logged-in user's posts the other user
# has liked and which tags they've both blogged about.
query = """
MATCH (they:User {username: {they} })
MATCH (you:User {username: {you} })
OPTIONAL MATCH (they)-[:PUBLISHED]->(:Post)<-[:TAGGED]-(tag:Tag),
(you)-[:PUBLISHED]->(:Post)<-[:TAGGED]-(tag)
RETURN SIZE((they)-[:LIKED]->(:Post)<-[:PUBLISHED]-(you)) AS likes,
COLLECT(DISTINCT tag.name) AS tags
"""
return graph.cypher.execute(query, they=other.username, you=self.username)[0]
Both common and similar are passed to the profile.html template, which displays whichever is appropriate. similar is diplayed if the user is viewing their own profile, and common is displayed if they’re visiting someone else’s profile:
{% extends "layout.html" %}
{% block body %}
<h2>{{ username }}'s profile</h2>
{% if session.username %}
{% if session.username == username %}
<h3>Users similar to you:</h3>
{% for user in similar %}
<p>
<a href="{{ url_for('profile', username=user.similar_user) }}">{{ user.similar_user }}</a>
also blogs about <i>{{ ", ".join(user.tags) }}</i>
</p>
{% else %}
<p>There aren't any users who've blogged about the same tags as you!</p>
{% endfor %}
<h3>Your recent posts:</h3>
{% else %}
<p>{{ username }} has liked {{ common.likes }} of your posts and
{% if common.tags %}
also blogs about <i>{{ ", ".join(common.tags) }}</i>
{% else %}
hasn't blogged about any of the same tags
{% endif %}
</p>
<h3>{{ username }}'s recent posts:</h3>
{% endif %}
{% endif %}
{% include "display_posts.html" %}
{% endblock %}