def application(environ, start_response):    
    status = '200 OK'    
    response_headers = [('Content-type', 'text/plain'), ('Content-Length', str(len(output)))]    
    start_response(status, response_headers)    
    return ['Hello World!']

import os
os.chdir(os.path.dirname(__file__))
import bottle
import main
application = bottle.default_app()

import bottle
@route('/')
def main():
    return "hello world!"

import main
ImportError: No module named main

import os
import sys

path = os.path.dirname(__file__)
sys.path.append(path)
os.chdir(path)

import bottle
import main

application = bottle.default_app()