Ansible Lookup plugin (v1.x) to get list of AWS EC2 Instance IDs given the value of Name tag

lookup_ec2.py

# A Lookup plugin to lookup EC2 instance IDs with given Name tag

# The plugin accepts instance name, i.e. the value for Name tag
# and returns a list of Instance IDs with that Name tag

# USAGE:
# - debug: msg="{{ lookup('lookup_ec2', instance_name) }}"
# OR
# with_lookup_ec2: "{{ instance_name }}"

from ansible.errors import *

from ansible import utils, errors
try:
    import boto.ec2
except ImportError:
    raise AnsibleError("Failed to load boto.ec2 while running lookup_ec2")

class LookupModule(object):

    def __init__(self, basedir=None, **kwargs):
        self.basedir = basedir

    def run(self, terms, inject=None, **kwargs):
        instance_name = terms
        region = 'us-west-2'
        try:
            list_instances = describe_instances(instance_name,region)
        except:
            raise AnsibleError("Ansible error during lookup of instance: %s" % instance_name)

        return list_instances

def describe_instances(instance_name,region):
    list_instances = []
    con = boto.ec2.connect_to_region(region)
    reservations = con.get_all_instances(filters={"tag:Name" : instance_name})
    for r in reservations:
        for instances in r.instances:
            list_instances.append(instances.id)
    if len(list_instances) > 0:
       return list_instances
    else:
       print("Lookup result: No instance found")
       return None