bottle json issure

i want use my json lib in bottle,but encouter some error as follows:
function not has write attribute,
i think the problem is bottle also contain a class named json,
so i use from lib import json as jsonpy replace,it fix a part,
another problem is some operate need write permission so we need chmod 777 web.py to give the write permission.

in default bottle catch all excpetion,so we can't see where is the issue,config as follows:
bottle.debug(True)

myapp = bottle.default_app() # or bottle.app() since 0.7
myapp.catchall = False

bottle.run(host='localhost',port=8080,reloader=True)
if you run bottle on 80 port ,you need sudo python web.py(you need root permission)