[Zope] why can't I create a External Method?

Hello,everyone. I have created a file in the /Extensions directory called 'member_csv.py', in which I had definded a function called 'write'. Then in the zope I wanted to create a External Method called 'exportData', Id=exportData, module name= member_csv, function name= write. But I failed. the error is ' can't find the web, please connect with 127.0.0.1'. I need your help, thank you. Leiz