Accessing value boto3 dictionary response

Question

I'm having an error trying to get a value out of data returned from boto3. I'm able to print the entire response (see below) but can't figure out what I need to do to get the NetworkInterfaceId out of response.

I'm running this in Python 2.7.5 because that's what the instances that need to run it have by default. I'm new to python so hope I'm missing some simple, thanks for your help!

Error

TypeError: list indices must be integers, not str

Code

#!/usr/bin/python
import boto3

ec2 = boto3.client('ec2')
response = ec2.describe_route_tables(
              RouteTableIds=[
                  "rtb-4a1efc23",
              ],
              Filters=[
                  {
                      'Name': 'route.destination-cidr-block',
                      'Values': [
                          "172.29.0.0/16",
                      ]
                  },
              ]
          )

#print(response)
print(response["RouteTables"][0]["Routes"]["NetworkInterfaceId"])

Response

 {'ResponseMetadata': {'RetryAttempts': 0, 'HTTPStatusCode': 200, 'RequestId': 'a8e7ba60-7599-450a-a708-8d90e429d59e', 'HTTPHeaders': {'transfer-encoding': 'chunked', 'vary': 'Accept-Encoding', 'server': 'AmazonEC2', 'content-type': 'text/xml;charset=UTF-8', 'date': 'Wed, 08 Feb 2017 11:51:47 GMT'}}, u'RouteTables': [{u'Associations': [{u'SubnetId': 'subnet-d7040aaf', u'RouteTableAssociationId': 'rtbassoc-867a94ef', u'Main': False, u'RouteTableId': 'rtb-4a1efc23'}, {u'SubnetId': 'subnet-e0fcd3aa', u'RouteTableAssociationId': 'rtbassoc-9f7a94f6', u'Main': False, u'RouteTableId': 'rtb-4a1efc23'}], u'RouteTableId': 'rtb-4a1efc23', u'VpcId': 'vpc-0d00e264', u'PropagatingVgws': [{u'GatewayId': 'vgw-fcf479cc'}], u'Tags': [{u'Value': 'pub', u'Key': 'Name'}], u'Routes': [{u'GatewayId': 'local', u'DestinationCidrBlock': '172.28.0.0/16', u'State': 'active', u'Origin': 'CreateRouteTable'}, {u'Origin': 'CreateRoute', u'DestinationCidrBlock': '172.29.0.0/16', u'InstanceId': 'i-0b84e502d9dc49443', u'NetworkInterfaceId': 'eni-08f55373', u'State': 'active', u'InstanceOwnerId': '444456106883'}, {u'Origin': 'CreateRoute', u'DestinationCidrBlock': '172.31.0.0/16', u'InstanceId': 'i-0b84e502d9dc49443', u'NetworkInterfaceId': 'eni-08f55373', u'State': 'active', u'InstanceOwnerId': '444456106883'}, {u'GatewayId': 'igw-7b03e012', u'DestinationCidrBlock': '0.0.0.0/0', u'State': 'active', u'Origin': 'CreateRoute'}, {u'GatewayId': 'vgw-fcf479cc', u'DestinationCidrBlock': '10.114.112.192/27', u'State': 'active', u'Origin': 'EnableVgwRoutePropagation'}, {u'GatewayId': 'vgw-fcf479cc', u'DestinationCidrBlock': '10.114.210.160/27', u'State': 'active', u'Origin': 'EnableVgwRoutePropagation'}, {u'GatewayId': 'vgw-fcf479cc', u'DestinationCidrBlock': '10.138.172.32/27', u'State': 'active', u'Origin': 'EnableVgwRoutePropagation'}, {u'GatewayId': 'vgw-fcf479cc', u'DestinationCidrBlock': '10.138.172.96/27', u'State': 'active', u'Origin': 'EnableVgwRoutePropagation'}, {u'GatewayId': 'vgw-fcf479cc', u'DestinationCidrBlock': '10.114.105.128/26', u'State': 'active', u'Origin': 'EnableVgwRoutePropagation'}, {u'GatewayId': 'vgw-fcf479cc', u'DestinationCidrBlock': '10.115.80.0/26', u'State': 'active', u'Origin': 'EnableVgwRoutePropagation'}, {u'GatewayId': 'vgw-fcf479cc', u'DestinationCidrBlock': '10.115.131.0/26', u'State': 'active', u'Origin': 'EnableVgwRoutePropagation'}, {u'GatewayId': 'vgw-fcf479cc', u'DestinationCidrBlock': '10.138.17.128/26', u'State': 'active', u'Origin': 'EnableVgwRoutePropagation'}, {u'GatewayId': 'vgw-fcf479cc', u'DestinationCidrBlock': '10.138.83.64/26', u'State': 'active', u'Origin': 'EnableVgwRoutePropagation'}, {u'GatewayId': 'vgw-fcf479cc', u'DestinationCidrBlock': '10.138.180.128/26', u'State': 'active', u'Origin': 'EnableVgwRoutePropagation'}, {u'GatewayId': 'vgw-fcf479cc', u'DestinationCidrBlock': '10.192.0.0/16', u'State': 'active', u'Origin': 'EnableVgwRoutePropagation'}]}]} 

Answer 1

From the documentation, you can find that Routes is a list. If you want to fetch the NetworkInterfaceId, you should loop through Routes.

for route in response["RouteTables"][0]['Routes']:
    if 'NetworkInterfaceId' in route:
        print route['NetworkInterfaceId']

Note that NetworkInterfaceId may or may not be present in the response. I figured that out from the response you have pasted here.