覆盖__getattr__会导致help（...）因TypeError而失败

Question

我有一个容器类（从列表中继承）我已经覆盖了 geattr 方法;

def __getattr__(self, name):
    def _multiplexed(*args, **kwargs):
        return [getattr(R, name)(*args, **kwargs) for R in self]
    return _multiplexed

麻烦的是，现在我无法向Python请求有关我的对象的帮助。当我请求帮助时，我得到（从iPython追溯）下面复制的错误。

所以问题是：如何覆盖 getattr 而不会失去我的求助能力？

谢谢， 杰里米

help(Collect)
/home/jlconlin/CustomPython/trunk/Collect.py in <module>()
----> 1 
      2 
      3 
      4 
      5 

/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site.pyc in __call__(self, *args, **kwds)
    455     def __call__(self, *args, **kwds):
    456         import pydoc
--> 457         return pydoc.help(*args, **kwds)
    458 
    459 def sethelper():

/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pydoc.pyc in __call__(self, request)
   1721     def __call__(self, request=None):
   1722         if request is not None:
-> 1723             self.help(request)
   1724         else:
   1725             self.intro()

/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pydoc.pyc in help(self, request)
   1768             elif request: doc(request, 'Help on %s:')
   1769         elif isinstance(request, Helper): self()
-> 1770         else: doc(request, 'Help on %s:')
   1771         self.output.write('\n')
   1772 

/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pydoc.pyc in doc(thing, title, forceload)
   1506     """Display text documentation, given an object or a path to an object."""
   1507     try:
-> 1508         pager(render_doc(thing, title, forceload))
   1509     except (ImportError, ErrorDuringImport), value:
   1510         print value

/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pydoc.pyc in render_doc(thing, title, forceload)
   1483     desc = describe(object)
   1484     module = inspect.getmodule(object)
-> 1485     if name and '.' in name:
   1486         desc += ' in ' + name[:name.rfind('.')]
   1487     elif module and module is not object:

TypeError: argument of type 'function' is not iterable

Answer 1

查看pydoc源代码，罪魁祸首是：

getattr(thing, '__name__', None)

尝试查找thing.__name__，如果失败，则返回None。除了你的情况，它不会失败;它会从__getattr__返回一个值。

如果你要覆盖__getattr__，那么特殊情况下所有特殊属性都是个好主意。类似的东西：

if name.startswith("__"):
    raise AttributeError

这可以确保如果您的类没有特定的特殊属性（在本例中为__name__），则查找它将失败，而不是产生意外值。