given an IP address, return the EC2 region it originates from

ec2_region_from_ip.py

# requires IPy https://github.com/haypo/python-ipy

from IPy import IP

# putting EC2_REGIONS here so the map only has to be performed once.
# I'm not sure if this is a great idea. Comments?
# ideally this list will be scraped from the following source
# https://forums.aws.amazon.com/ann.jspa?annID=857
# thanks to serverfault.com user Flashman for pointing me to this doc.

EC2_REGIONS = { "asia_pacific_singapore" : map(IP,[ "175.41.128.0/18" ]),
  "eu_ireland" : map(IP,[ "79.125.0.0/17",
      "46.51.128.0/18",
      "46.51.192.0/20",
      "46.137.0.0/17"
    ]),
  "us_east" : map(IP,[ "216.182.224.0/20",
      "72.44.32.0/19",
      "67.202.0.0/18",
      "67.202.0.0/18",
      "75.101.128.0/17",
      "174.129.0.0/16",
      "204.236.192.0/18",
      "184.73.0.0/16",
      "184.72.128.0/17",
      "184.72.64.0/18",
      "50.16.0.0/15"
    ]),
  "us_west" : map(IP,[ "204.236.128.0/18",
      "184.72.0.0/18",
      "50.18.0.0/18"
    ])
}

def ec2_region(address):
	""" given an ip address, returns the EC2 region, if applicable
	otherwise return None """
	# ip ranges curated from https://forums.aws.amazon.com/ann.jspa?annID=857
	# we might want to make a scraper or a batch job that keeps these current

	for key,region in EC2_REGIONS.iteritems():
		if any([address in x for x in region]):
			return key
	return None