Compute the count of instances per zone

instance.py

import simplejson as json
import sys 

#{
#  "results": 91,
#  "rows": [
#    {
#      "ec2": {
#        "instance_action": "none",
#        "instance_id": "i-f9069c96",
#        "ami_launch_index": "0",

# z is a hash {zone: {type: count}}
z = {}

x = json.load(sys.stdin)
for r in x["rows"]:
    if r["ec2"].get("placement_availability_zone") is None: continue
    zone = r["ec2"]["placement_availability_zone"]
    typ = r["ec2"]["instance_type"]
    if z.get(zone) is None: z[zone] = {}
    if z[zone].get(typ) is None: z[zone][typ] = 0 
    z[zone][typ] += 1

for zone in z:
    for typ in z[zone]:
        print("{0},{1},{2}".format(zone, typ, z[zone][typ]))

knife search node "role:common-node" -a ec2 -Fj | python instance.py