based on https://github.com/natevw/ShutterStem/blob/2a1ad2db119a19e2cd192d52056ac682a50b27f6/_attachments/scripts/couch.py in response to https://gist.github.com/1238181 based on http://wiki.apache.org/couchdb/ExternalProcesses#Example_External_Process

Python CouchDB External example

import sys, json

class External(object):
    def run(self):
        line = sys.stdin.readline()
        while line:
            try:
                response = self.process(json.loads(line.decode('utf_8')))
            except Exception, e:
                response = {'code':500, 'json':{'error':True, 'reason':"Internal error processing request (%s)" % e}}
            sys.stdout.write("%s\n" % json.dumps(response))
            sys.stdout.flush()
            line = sys.stdin.readline()
    
    def process(self, req):
        res = {}
        # TODO: set res['body'] or res['json'] based on req['method']/req['body']/req['path']/etc.
        return res

class External(object):
    def run(self, part='body'):
        line = sys.stdin.readline()
        while line:
            try:
                return self.process(json.loads(line.decode('utf_8')), part)
            except Exception, e:
                logger.exception(e)
                response = {'code':500, 'json':{'error':True, 'reason':"Internal error processing request (%s)" % e}}
                sys.stdout.write("%s\n" % json.dumps(response))
                sys.stdout.flush()
                line = sys.stdin.readline()

    def process(self, req, part):
        res = req[part]
        # TODO: set res['body'] or res['json'] based on req['method']/req['body']/req['path']/etc.
        return res

    def respond(self, code=200, data={}, headers={}):
            sys.stdout.write("%s\n" % json.dumps({"code": code, "json": data, "headers": headers}))
            sys.stdout.flush()

Created another class to extend it:

import sys
import os
import json
import Greenlight

import logging
logger = logging.getLogger('myapp')
hdlr = logging.FileHandler('/tmp/password.log')
formatter = logging.Formatter('%(asctime)s %(levelname)s %(message)s')
hdlr.setFormatter(formatter)
logger.addHandler(hdlr) 
logger.setLevel(logging.INFO)

class password_checker(Greenlight.External):

    def main(self):
        # for req in requests():
        #   respond(data={"response": req['query']})

        logger.info('running')
        data = self.run(part='query')

        logger.info('logging response:')
        logger.info(data)
        logger.info(data['fieldValue'])
        pwl = Greenlight.Passwordlist()
        pw = pwl.valid(data['fieldValue'])
        if data['fieldValue'] == pw:
            self.respond(data=['password', True, 'This password is good!'])
        else:
            self.respond(data=['password', False, 'This password is too common'])

if __name__ == "__main__":
    try:
        logger.info('running')
        pw = password_checker()
        pw.main()
    except Exception, e:
        logger.info('Error')
        logger.exception(e)

The password_checker is my external... and it only runs on 1,3,5 etc attempts... no log output whatsoever on 2,4,6,etc