Python 实战（1）：在网页上显示信息

布拉格广场

Traceback (most recent call last):
  File "D:\python\lib\site-packages\web.py-0.40.dev0-py3.6.egg\web\application.py", line 257, in process
    return self.handle()
  File "D:\python\lib\site-packages\web.py-0.40.dev0-py3.6.egg\web\application.py", line 248, in handle
    return self._delegate(fn, self.fvars, args)
  File "D:\python\lib\site-packages\web.py-0.40.dev0-py3.6.egg\web\application.py", line 487, in _delegate
    cls = fvars[f]
KeyError: 'index'

127.0.0.1:61127 - - [16/Jun/2017 20:01:54] "HTTP/1.1 GET /" - 500 Internal Server Error
127.0.0.1:61127 - - [16/Jun/2017 20:01:55] "HTTP/1.1 GET /favicon.ico" - 404 Not Found



这个问题是什么原因呢？