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ably / ably-python

Python client library SDK for Ably realtime messaging service
https://ably.com/download
Apache License 2.0
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client-library python rest sdk

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ably-python

.github/workflows/check.yml Features PyPI version

Overview

This is a Python client library for Ably. The library currently targets the Ably 2.0 client library specification.

Running example

import asyncio
from ably import AblyRest

async def main():
    async with AblyRest('api:key') as ably:
        channel = ably.channels.get("channel_name")

if __name__ == "__main__":
    asyncio.run(main())

Installation

Via PyPI

The client library is available as a PyPI package.

pip install ably

Or, if you need encryption features:

pip install 'ably[crypto]'

Via GitHub

git clone --recurse-submodules https://github.com/ably/ably-python.git
cd ably-python
python setup.py install

Upgrade / Migration Guide

Please see our Upgrade / Migration Guide for notes on changes you need to make to your code to update it to use the new APIs when migrating from older versions.

Usage

Using the Rest API

[!NOTE]
Please note that since version 2.0.2 we also provide a synchronous variant of the REST interface which is can be accessed as from ably.sync import AblyRestSync.

All examples assume a client and/or channel has been created in one of the following ways:

With closing the client manually:

from ably import AblyRest

async def main(): 
    client = AblyRest('api:key')
    channel = client.channels.get('channel_name')
    await client.close()

When using the client as a context manager, this will ensure that client is properly closed while leaving the with block:

from ably import AblyRest

async def main():
    async with AblyRest('api:key') as ably:
        channel = ably.channels.get("channel_name")

You can define the logging level for the whole library, and override for a specific module:

import logging
import ably

logging.getLogger('ably').setLevel(logging.WARNING)
logging.getLogger('ably.rest.auth').setLevel(logging.INFO)

You need to add a handler to see any output:

logger = logging.getLogger('ably')
logger.addHandler(logging.StreamHandler())

Publishing a message to a channel

await channel.publish('event', 'message')

If you need to add metadata when publishing a message, you can use the Message constructor to create a message with custom fields:

from ably.types.message import Message

message_object = Message(name="message_name",
                         data="payload",
                         extras={"headers": {"metadata_key": "metadata_value"}})
await channel.publish(message_object)

Querying the History

message_page = await channel.history() # Returns a PaginatedResult
message_page.items # List with messages from this page
message_page.has_next() # => True, indicates there is another page
next_page = await message_page.next() # Returns a next page
next_page.items # List with messages from the second page

Current presence members on a channel

members_page = await channel.presence.get() # Returns a PaginatedResult
members_page.items
members_page.items[0].client_id # client_id of first member present

Querying the presence history

presence_page = await channel.presence.history() # Returns a PaginatedResult
presence_page.items
presence_page.items[0].client_id # client_id of first member

Getting the channel status

channel_status = await channel.status() # Returns a ChannelDetails object
channel_status.channel_id # Channel identifier
channel_status.status # ChannelStatus object
channel_status.status.occupancy # ChannelOccupancy object
channel_status.status.occupancy.metrics # ChannelMetrics object

Symmetric end-to-end encrypted payloads on a channel

When a 128 bit or 256 bit key is provided to the library, all payloads are encrypted and decrypted automatically using that key on the channel. The secret key is never transmitted to Ably and thus it is the developer's responsibility to distribute a secret key to both publishers and subscribers.

key = ably.util.crypto.generate_random_key()
channel = rest.channels.get('communication', cipher={'key': key})
channel.publish(u'unencrypted', u'encrypted secret payload')
messages_page = await channel.history()
messages_page.items[0].data #=> "sensitive data"

Generate a Token

Tokens are issued by Ably and are readily usable by any client to connect to Ably:

token_details = await client.auth.request_token()
token_details.token # => "xVLyHw.CLchevH3hF....MDh9ZC_Q"
new_client = AblyRest(token=token_details)
await new_client.close()

Generate a TokenRequest

Token requests are issued by your servers and signed using your private API key. This is the preferred method of authentication as no secrets are ever shared, and the token request can be issued to trusted clients without communicating with Ably.

token_request = await client.auth.create_token_request(
    {
        'client_id': 'jim',
        'capability': {'channel1': '"*"'},
        'ttl': 3600 * 1000, # ms
    }
)
# => {"id": ...,
#     "clientId": "jim",
#     "ttl": 3600000,
#     "timestamp": ...,
#     "capability": "{\"*\":[\"*\"]}",
#     "nonce": ...,
#     "mac": ...}

new_client = AblyRest(token=token_request)
await new_client.close()

Fetching your application's stats

stats = await client.stats() # Returns a PaginatedResult
stats.items
await client.close()

Fetching the Ably service time

await client.time()
await client.close()

Using the realtime client

Create a client using an API key

from ably import AblyRealtime

# Create a client using an Ably API key
async def main():
    client = AblyRealtime('api:key')

Create a client using token auth

# Create a client using kwargs, which must contain at least one auth option
# the available auth options are key, token, token_details, auth_url, and auth_callback
# see https://www.ably.com/docs/rest/usage#client-options for more details
from ably import AblyRealtime
from ably import AblyRest
async def main():
    rest_client = AblyRest('api:key')
    token_details = rest_client.request_token()
    client = AblyRealtime(token_details=token_details)

Subscribe to connection state changes

# subscribe to 'failed' connection state
client.connection.on('failed', listener)

# subscribe to 'connected' connection state
client.connection.on('connected', listener)

# subscribe to all connection state changes
client.connection.on(listener)

# wait for the next state change
await client.connection.once_async()

# wait for the connection to become connected
await client.connection.once_async('connected')
# subscribe to 'failed' connection state
client.connection.on('failed', listener)

# subscribe to 'connected' connection state
client.connection.on('connected', listener)

# subscribe to all connection state changes
client.connection.on(listener)

# wait for the next state change
await client.connection.once_async()

# wait for the connection to become connected
await client.connection.once_async('connected')

Get a realtime channel instance

channel = client.channels.get('channel_name')

Subscribing to messages on a channel


def listener(message):
    print(message.data)

# Subscribe to messages with the 'event' name
await channel.subscribe('event', listener)

# Subscribe to all messages on a channel
await channel.subscribe(listener)

Note that channel.subscribe is a coroutine function and will resolve when the channel is attached

Unsubscribing from messages on a channel

# unsubscribe the listener from the channel
channel.unsubscribe('event', listener)

# unsubscribe all listeners from the channel
channel.unsubscribe()

Attach to a channel

await channel.attach()

Detach from a channel

await channel.detach()

Managing a connection

# Establish a realtime connection.
# Explicitly calling connect() is unnecessary unless the autoConnect attribute of the ClientOptions object is false
client.connect()

# Close a connection
await client.close()

# Send a ping
time_in_ms = await client.connection.ping()

Resources

Visit https://ably.com/docs for a complete API reference and more examples.

Requirements

This SDK supports Python 3.7+.

We regression-test the SDK against a selection of Python versions (which we update over time, but usually consists of mainstream and widely used versions). Please refer to check.yml for the set of versions that currently undergo CI testing.

Known Limitations

Currently, this SDK only supports Ably REST and realtime message subscription as documented above. However, you can use the MQTT adapter to implement Ably's Realtime features using Python.

See our roadmap for this SDK for more information.

Support, feedback and troubleshooting

Please visit https://ably.com/support for access to our knowledge base and to ask for any assistance.

You can also view the community reported GitHub issues.

To see what has changed in recent versions of Bundler, see the CHANGELOG.

If you find any compatibility issues, please do raise an issue in this repository or contact Ably customer support for advice.

Contributing

For guidance on how to contribute to this project, see CONTRIBUTING.md