Python script to assess EC2 Reserved Instance usage

RIstats.py

#!/usr/bin/env python3
import boto3
from collections import defaultdict

ris = boto3.client("ec2").describe_reserved_instances()["ReservedInstances"]
ri_counts = defaultdict(lambda: 0)
for ri in ris:
    if ri["State"] == "active":
        ri_counts[ri["InstanceType"]] += ri["InstanceCount"]

instances = boto3.client("ec2").describe_instances(
    Filters=[{"Name": "instance-state-name", "Values": ["running"]}]
)
inst_counts = defaultdict(lambda: 0)
for res in instances["Reservations"]:
    for i in res["Instances"]:
        inst_counts[i["InstanceType"]] += 1

MULTS = {
    "micro": 1,
    "small": 2,
    "medium": 4,
    "large": 8,
    "xlarge": 16,
    "2xlarge": 32,
    "4xlarge": 64,
    # TODO: fill in any more you need
}

def convert_to_micro(counts):
    ret = defaultdict(lambda: 0)
    for t, n in counts.items():
        series, size = t.split(".")
        ret[series] += MULTS[size] * n
    return ret

reserved = convert_to_micro(ri_counts)
running = convert_to_micro(inst_counts)

print("Instance counts in .micro size equivalent:\n"
      "Type | # Reserved | # Running\n"
      "-----------------------------")
for t in running:
    reserved[t] += 0 # ensure reserved.keys() includes running.keys()
for t in reserved:
    print("% 4s | % 10d | % 9d" % (t, reserved[t], running[t]))