tornado get_argument 代码

def get_argument(self, name, default=_ARG_DEFAULT, strip=True):
"""Returns the value of the argument with the given name.

If default is not provided, the argument is considered to be
required, and we throw an HTTP 400 exception if it is missing.

If the argument appears in the url more than once, we return the
last value.

The returned value is always unicode.
"""
args = self.get_arguments(name, strip=strip)
if not args:
if default is self._ARG_DEFAULT:
raise HTTPError(400, "Missing argument %s" % name)
return default
return args[-1]

这个如果不设默认值，如果获取失败会抛出异常，感觉合理吗？