How to extend a Boto3 resource?

Question

On boto3, how can I extend ResourceModel? What I wan't to do is subclass boto3.resources.factory.ec2.Instance and add a run method to it. That method would be used to remotely run commands on the EC2 instance represented by the Python object, via SSH. I wish to do this in a clean way, i.e., without resorting to monkey patches or other obscure techniques.

Update

Based on Daniel's answer, I came up with the following code. Requires a recent version of Boto 3, and Spur for the SSH connection (pip install spur boto3).

from boto3 import session
from shlex import split
from spur import SshShell

# Customize here.
REGION = 'AWS-REGION'
INSTID = 'AWS-INSTANCE-ID'
USERID = 'SSH-USER'

def hook_ssh(class_attributes, **kwargs):
    def run(self, command):
        '''Run a command on the EC2 instance via SSH.'''

        # Create the SSH client.
        if not hasattr(self, '_ssh_client'):
            self._ssh_client = SshShell(self.public_ip_address, USERID)

        print(self._ssh_client.run(split(command)).output.decode())

    class_attributes['run'] = run

if __name__ == '__main__':
    b3s = session.Session()
    ec2 = b3s.resource('ec2', region_name=REGION)

    # Hook the "run" method to the "ec2.Instance" resource class.
    b3s.events.register('creating-resource-class.ec2.Instance', hook_ssh)

    # Run some commands.
    ec2.Instance(INSTID).run('uname -a')
    ec2.Instance(INSTID).run('uptime')

Answer 1

The short answer is that this isn't yet possible but it is planned to allow customizations of this sort. You can already see them in action with the new upload_file and download_file customization available on the S3 client. The plan is to use that same sort of mechanism for Boto 3 resources.

1. Resources will fire some kind of event when creating a class that includes the attribute dict of all methods/attributes
2. You hook your own method into the attribute dict
3. The class gets created with your custom method - no monkey-patching required.

Take a look here:

https://github.com/boto/boto3/blob/develop/boto3/session.py#L314-L318 https://github.com/boto/boto3/tree/develop/boto3/s3

Boto 3 extensibility is definitely on our radar.