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Quick start: Python¶
In this tutorial you’ll build a Media Player app to store your songs and create playlists.
1. Get the development environment ready¶
1.1 Prerequisites:¶
2.2 Set up the environment¶
Create a new folder for the project:
mkdir scylladb-cloud-python
cd scylladb-cloud-python
Create a new virtual environment and activate it:
virtualenv env
source env/bin/activate
Install the Python ScyllaDB Driver.
pip install scylla-driver
2. Connect to the Cluster¶
Get your database credentials from your ScyllaDB Cloud Dashboard in the tab Connect.
Add your machine’s IP Address to the list of allowed IP addresses in ScyllaDB Cloud. Otherwise, your connection will get refused.
from cassandra.cluster import Cluster
from cassandra.auth import PlainTextAuthProvider
cluster = Cluster(
contact_points=[
"your-node-url-1.clusters.scylla.cloud",
"your-node-url-2.clusters.scylla.cloud",
"your-node-url-3.clusters.scylla.cloud",
],
auth_provider=PlainTextAuthProvider(username='scylla', password='your-awesome-password')
)
3. Handling Queries¶
With the Python driver, you can use the function inside your cluster connection called execute(query) and build the query you want to execute inside your database/keyspace. You also can use the execute_async() for asynchronous queries.
from cassandra.cluster import Cluster
from cassandra.auth import PlainTextAuthProvider
cluster = Cluster(
contact_points=[
"your-node-url-1.clusters.scylla.cloud",
"your-node-url-2.clusters.scylla.cloud",
"your-node-url-3.clusters.scylla.cloud",
],
auth_provider=PlainTextAuthProvider(username='scylla', password='your-awesome-password')
)
session = cluster.connect()
results = session.execute('SELECT * FROM system.clients LIMIT 10')
for item in results:
print(item)
print(item.address)
Response will be a ResultSet of Rows:
Row(address='123.123.123.123', port=46160, client_type='cql', connection_stage='AUTHENTICATING', driver_name='Scylla Python Driver', driver_version='3.26.2', hostname=None, protocol_version=4, shard_id=0, ssl_cipher_suite=None, ssl_enabled=None, ssl_protocol=None, username='scylla')
123.123.123.123
3.1 Create a Keyspace¶
The keyspace inside the ScyllaDB ecosystem can be interpreted as your database or collection.
On your connection boot, you don’t need to provide it but you will use it later and also is able to create when you need.
{% raw %}
from cassandra.cluster import Cluster
from datetime import datetime
from cassandra.auth import PlainTextAuthProvider
cluster = Cluster(
contact_points=[
"your-node-url-1.clusters.scylla.cloud",
"your-node-url-2.clusters.scylla.cloud",
"your-node-url-3.clusters.scylla.cloud",
],
auth_provider=PlainTextAuthProvider(username='scylla', password='your-awesome-password')
)
session = cluster.connect()
keyspaceName = "media_player"
replicationFactor = 3
session.execute(
"""
CREATE KEYSPACE {}
WITH replication = {{'class': 'NetworkTopologyStrategy', 'replication_factor': '{}'}}
AND durable_writes = true;
""".format(keyspaceName, replicationFactor)
)
session.set_keyspace('media_player')
{% endraw %}
Unfortunately you can’t set a keyspace with PreparedStatements, so you will need to build the query by yourself.
You can use the
session.set_keyspace()function to switch between keyspaces.
3.2 Creating a Table¶
A table is used to store a part or all of your app data (depending on how you structure your database schema).
Add the keyspace as a parameter in the connection object and define a CQL string that creates a table to store your favorite songs.
from cassandra.cluster import Cluster
from datetime import datetime
from cassandra.auth import PlainTextAuthProvider
cluster = Cluster(
contact_points=[
"your-node-url-1.clusters.scylla.cloud",
"your-node-url-2.clusters.scylla.cloud",
"your-node-url-3.clusters.scylla.cloud",
],
auth_provider=PlainTextAuthProvider(username='scylla', password='your-awesome-password')
)
session = cluster.connect('media_player')
tableQuery = """
CREATE TABLE songs (
id uuid,
title text,
album text,
artist text,
created_at timestamp,
PRIMARY KEY (id, created_at)
)
"""
session.execute(tableQuery)
3.3 Insert data¶
Now that you have created a keyspace and a table, insert some songs to populate the table.
from cassandra.cluster import Cluster
from datetime import datetime
from cassandra.auth import PlainTextAuthProvider
import uuid
cluster = Cluster(
contact_points=[
"your-node-url-1.clusters.scylla.cloud",
"your-node-url-2.clusters.scylla.cloud",
"your-node-url-3.clusters.scylla.cloud",
],
auth_provider=PlainTextAuthProvider(username='scylla', password='your-awesome-password')
)
session = cluster.connect('media_player')
songList = [
{
"id": uuid.UUID('d754f8d5-e037-4898-af75-44587b9cc424'),
"title": 'Glimpse of Us',
"album": 'Smithereens',
"artist": 'Joji',
"createdAt": datetime.now(),
},
{
"id": uuid.uuid4(),
"title": 'Stairway to Heaven',
"album": 'Led Zeppelin III',
"artist": 'Led Zeppelin',
"createdAt": datetime.now(),
},
{
"id": uuid.uuid4(),
"title": 'Vegas',
"album": 'From Movie ELVIS',
"artist": 'Doja Cat',
"createdAt": datetime.now(),
},
];
query = session.prepare("""
INSERT INTO songs (id, title, album, artist, created_at) VALUES (?, ?, ?, ?, ?)
""")
for music in songList:
session.execute(query, music.values())
3.3 Read data¶
Since probably we added more than 3 songs into our database, let’s list it into our terminal.
from cassandra.cluster import Cluster
from datetime import datetime
from cassandra.auth import PlainTextAuthProvider
cluster = Cluster(
contact_points=[
"your-node-url-1.clusters.scylla.cloud",
"your-node-url-2.clusters.scylla.cloud",
"your-node-url-3.clusters.scylla.cloud",
],
auth_provider=PlainTextAuthProvider(username='scylla', password='your-awesome-password')
)
session = cluster.connect('media_player')
query = session.prepare("SELECT * FROM songs");
results = session.execute(query);
for song in results:
print(song.id)
print(song.title)
The result looks like this:
0a5d5cfb-0275-43a4-9523-45ad256666f8
Vegas
3.4 Update data¶
The UPDATE query in the fact is equals to INSERT regarding the syntax. You just need the Partition Key and Clustering Key (if you have one) and query it.
The UPDATE query takes two fields in the WHERE clause (PK and CK). See the snippet below:
from cassandra.cluster import Cluster
from datetime import datetime
from cassandra.auth import PlainTextAuthProvider
import uuid
cluster = Cluster(
contact_points=[
"your-node-url-1.clusters.scylla.cloud",
"your-node-url-2.clusters.scylla.cloud",
"your-node-url-3.clusters.scylla.cloud",
],
auth_provider=PlainTextAuthProvider(username='scylla', password='your-awesome-password')
)
session = cluster.connect('media_player')
songToUpdate = {
"id": uuid.UUID('d754f8d5-e037-4898-af75-44587b9cc424'),
"title": 'Glimpse of Us',
"album": '2022 Em Uma Música',
"artist": 'Lucas Inutilismo',
"createdAt": datetime.now()
}
session.execute("""
UPDATE songs SET
title = %(title)s,
album = %(album)s,
artist = %(artist)s
WHERE id = %(id)s AND created_at = %(createdAt)s
""", songToUpdate)
After the data gets inserted, query all columns and filter by the ID:
scylla@cqlsh:media_player> select * from songs where id = d754f8d5-e037-4898-af75-44587b9cc424;
id | created_at | album | artist | title
--------------------------------------+---------------------------------+--------------------+------------------+---------------
d754f8d5-e037-4898-af75-44587b9cc424 | 2023-07-11 14:22:43.329000+0000 | Smithereens | Joji | Glimpse of Us
d754f8d5-e037-4898-af75-44587b9cc424 | 2023-07-11 14:23:31.630000+0000 | 2022 Em Uma Música | Lucas Inutilismo | Glimpse of Us
d754f8d5-e037-4898-af75-44587b9cc424 | 2023-07-11 14:23:51.996000+0000 | 2022 Em Uma Música | null | Glimpse of Us
(3 rows)
In the snippet above, we updated the data fully but as you can see in the SELECT query, I ran one more update but without the artist column. So, as said before: the only “not nullable” fields are the Partition Keys and Clustering Keys.
3.5 Delete Data¶
Let’s understand what we can DELETE with this statement. There’s the normal DELETE statement that focuses on ROWS and another one that deletes data only from COLUMNS and the syntax is very similar.
// Deletes a single row
DELETE FROM songs WHERE id = d754f8d5-e037-4898-af75-44587b9cc424;
// Deletes a whole column
DELETE artist FROM songs WHERE id = d754f8d5-e037-4898-af75-44587b9cc424;
If you want to remove a specific column, you also should pass as parameter the Clustering Key and be very specific in which register you want to delete something.
On the other hand, the “normal delete” just need the Partition Key to handle it. Just remember: if you use the statement “DELETE FROM keyspace.table_name” it will delete ALL the rows that you stored with that ID.
from cassandra.cluster import Cluster
from datetime import datetime
from cassandra.auth import PlainTextAuthProvider
import uuid
songToDelete = {
"id": uuid.UUID('d754f8d5-e037-4898-af75-44587b9cc424'),
"title": 'Glimpse of Us',
"album": '2022 Em Uma Música',
"artist": 'Lucas Inutilismo',
"createdAt": datetime.now()
}
cluster = Cluster(
contact_points=[
"your-node-url-1.clusters.scylla.cloud",
"your-node-url-2.clusters.scylla.cloud",
"your-node-url-3.clusters.scylla.cloud",
],
auth_provider=PlainTextAuthProvider(username='scylla', password='your-awesome-password')
)
session = cluster.connect('media_player')
deleteQuery = session.prepare("DELETE FROM songs WHERE id = ? ")
session.execute(deleteQuery, [songToDelete['id']])
4. Conclusion¶
Yay! You now know how get started with ScyllaDB in Python.
If you think something can be improved, please open an issue and let’s make it happen!
There is a sample project that you can learn more about the concepts and also have a good time testing our ScyllaDB Cloud Cluster, check it out here.
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