Where in the world is Carmen Sandiego? If "Carmen Sandiego" is the cheapest spot price on AWS EC2:

listregions.py

import boto3

class Session(boto3.Session):
    def __enter__(self):
        return self
    def __exit__(self, *args):
        del self

with Session() as sess:
    # get names of regions
    client = sess.client('ec2')
    regions = client.describe_regions()
    region_names = [r['RegionName'] for r in regions['Regions']]

# funtion to get prices for an instance type
machine_type_args = dict(InstanceTypes=['m3.medium'],
                         MaxResults=1,
                         ProductDescriptions=['Linux/UNIX (Amazon VPC)'])
def read_spot_price(client, zone, **kwargs):
    prices = client.describe_spot_price_history(AvailabilityZone=zone, **kwargs)
    return prices['SpotPriceHistory'][0]

# iterate over all regions and availability zones
zones = {}
prices = []
for r in region_names:
    print(r)
    with Session(region_name=r) as sess:
        client = sess.client('ec2')
        response = client.describe_availability_zones()
        zones[r] = [r['ZoneName'] for r in response['AvailabilityZones']]
        for z in zones[r]:
            try:
                p = read_spot_price(client, z, **machine_type_args)
                prices.append((z, p['SpotPrice']))
            except IndexError:
                pass

# list zones, sorted by price
for z,p in sorted(prices, key=lambda x: x[1], reverse=True):
    print(z,p)