A sample tutorial¶

This tutorial will show you how to use Boto3 with an AWS service. In this sample tutorial, you will learn how to use Boto3 with Amazon Simple Queue Service (SQS)

SQS¶

SQS allows you to queue and then process messages. This tutorial covers how to create a new queue, get and use an existing queue, push new messages onto the queue, and process messages from the queue by using Resources and Collections.

Creating a queue¶

Queues are created with a name. You may also optionally set queue attributes, such as the number of seconds to wait before an item may be processed. The examples below will use the queue name test. Before creating a queue, you must first get the SQS service resource:

# Get the service resource
sqs = boto3.resource('sqs')

# Create the queue. This returns an SQS.Queue instance
queue = sqs.create_queue(QueueName='test', Attributes={'DelaySeconds': '5'})

# You can now access identifiers and attributes
print(queue.url)
print(queue.attributes.get('DelaySeconds'))

Reference: SQS.ServiceResource.create_queue()

Warning

The code above may throw an exception if you already have a queue named test.

Using an existing queue¶

It is possible to look up a queue by its name. If the queue does not exist, then an exception will be thrown:

# Get the service resource
sqs = boto3.resource('sqs')

# Get the queue. This returns an SQS.Queue instance
queue = sqs.get_queue_by_name(QueueName='test')

# You can now access identifiers and attributes
print(queue.url)
print(queue.attributes.get('DelaySeconds'))

It is also possible to list all of your existing queues:

# Print out each queue name, which is part of its ARN
for queue in sqs.queues.all():
    print(queue.url)

Note

To get the name from a queue, you must use its ARN, which is available in the queue's attributes attribute. Using queue.attributes['QueueArn'].split(':')[-1] will return its name.

Reference: SQS.ServiceResource.get_queue_by_name(), SQS.ServiceResource.queues

Sending messages¶

Sending a message adds it to the end of the queue:

# Get the service resource
sqs = boto3.resource('sqs')

# Get the queue
queue = sqs.get_queue_by_name(QueueName='test')

# Create a new message
response = queue.send_message(MessageBody='world')

# The response is NOT a resource, but gives you a message ID and MD5
print(response.get('MessageId'))
print(response.get('MD5OfMessageBody'))

You can also create messages with custom attributes:

queue.send_message(MessageBody='boto3', MessageAttributes={
    'Author': {
        'StringValue': 'Daniel',
        'DataType': 'String'
    }
})

Messages can also be sent in batches. For example, sending the two messages described above in a single request would look like the following:

response = queue.send_messages(Entries=[
    {
        'Id': '1',
        'MessageBody': 'world'
    },
    {
        'Id': '2',
        'MessageBody': 'boto3',
        'MessageAttributes': {
            'Author': {
                'StringValue': 'Daniel',
                'DataType': 'String'
            }
        }
    }
])

# Print out any failures
print(response.get('Failed'))

In this case, the response contains lists of Successful and Failed messages, so you can retry failures if needed.

Reference: SQS.Queue.send_message(), SQS.Queue.send_messages()

Processing messages¶

Messages are processed in batches:

# Get the service resource
sqs = boto3.resource('sqs')

# Get the queue
queue = sqs.get_queue_by_name(QueueName='test')

# Process messages by printing out body and optional author name
for message in queue.receive_messages(MessageAttributeNames=['Author']):
    # Get the custom author message attribute if it was set
    author_text = ''
    if message.message_attributes is not None:
        author_name = message.message_attributes.get('Author').get('StringValue')
        if author_name:
            author_text = ' ({0})'.format(author_name)

    # Print out the body and author (if set)
    print('Hello, {0}!{1}'.format(message.body, author_text))

    # Let the queue know that the message is processed
    message.delete()

Given only the messages that were sent in a batch with SQS.Queue.send_messages() in the previous section, the above code will print out:

Hello, world!
Hello, boto3! (Daniel)

Reference: SQS.Queue.receive_messages(), SQS.Message.delete()

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