Pagination in boto3 ec2 describe instance

Question

I am having an issue with pagination in boto3 & not getting all instances in the aws account.

Only getting 50% of the instances with below (around 2000 where as there are 4000)

Below is my code

import boto3

ec2 = boto3.client('ec2')

paginator = ec2.get_paginator('describe_instances')
response = paginator.paginate().build_full_result()

ec2_instance = response['Reservations']


for instance in ec2_instance:
    print(instance['Instances'][0]['InstanceId'])

Answer 1

The response from describe_instances() is:

{
    'Reservations': [
        {
            'Groups': [
                {
                    'GroupName': 'string',
                    'GroupId': 'string'
                },
            ],
            'Instances': [
                {
                    'AmiLaunchIndex': 123,
 ...

Notice that the response is:

• A dictionary
• Where Reservations is a list containing:
  • Instances, which is a list

Therefore, the code really needs to loop through all Reservations and instances.

At the moment, your code is looping through the Reservations (incorrectly calling them instances), and is then only retrieving the first ([0]) instance from that Reservation.

You'll probably want some code like this:

for reservation in response['Reservations']:
  for instance in reservation['Instances']:
    print(instance['InstanceId'])