返回 ipython 中对象的实例时使用了哪些属性？

Question

在 ipython 终端中，假设我创建了一个对象，然后只需键入该对象的名称并点击 return，该对象的 attributes/methods 是什么（以什么顺序）查询以生成 return 显示到屏幕的输出？

例如，

In [1]: from mymodule import myclass
In [2]: C = myclass()
In [3]: C # hit return
Out[3]:

查询 C 的哪些 attributes/methods 以生成 Out[3] 中的输出？

更新：从答案（以及我发现的，它表明调用了__repr__。但是，我有一个class 定义了 __repr__，但它似乎没有被使用，我收到以下回溯错误：

/usr/local/lib/python2.7/dist-packages/IPython/core/displayhook.pyc in __call__(self, result)
244             self.start_displayhook()
245             self.write_output_prompt()
--> 246             format_dict, md_dict = self.compute_format_data(result)
247             self.update_user_ns(result)
248             self.fill_exec_result(result)

/usr/local/lib/python2.7/dist-packages/IPython/core/displayhook.pyc in compute_format_data(self, result)
148 
149         """
--> 150         return self.shell.display_formatter.format(result)
151 
152     # This can be set to True by the write_output_prompt method in a subclass

/usr/local/lib/python2.7/dist-packages/IPython/core/formatters.pyc in format(self, obj, include, exclude)
150             return {}, {}
151 
--> 152         format_dict, md_dict = self.mimebundle_formatter(obj, include=include, exclude=exclude)
153 
154         if format_dict or md_dict:

<decorator-gen-12> in __call__(self, obj, include, exclude)

/usr/local/lib/python2.7/dist-packages/IPython/core/formatters.pyc in catch_format_error(method, self, *args, **kwargs)
215     """show traceback on failed format call"""
216     try:
--> 217         r = method(self, *args, **kwargs)
218     except NotImplementedError:
219         # don't warn on NotImplementedErrors

/usr/local/lib/python2.7/dist-packages/IPython/core/formatters.pyc in __call__(self, obj, include, exclude)
962                 return printer(obj)
963             # Finally look for special method names
--> 964             method = get_real_method(obj, self.print_method)
965 
966             if method is not None:

/usr/local/lib/python2.7/dist-packages/IPython/utils/dir2.pyc in get_real_method(obj, name)
 63 
 64     try:
---> 65         canary = getattr(obj, '_ipython_canary_method_should_not_exist_', None)
 66     except Exception:
 67         return None

最终它尝试使用 __getattr__ 方法！在我的 class 中，我有自己定义的 __getattr__ 方法，这会导致问题吗？

Answer 1

作为另一个答案，例如的答案一般说明 __repr__ 方法将被调用。

但是，ipython 会搜索 __repr__ 方法的其他特殊版本以在格式化输出时使用，例如，请参阅 [=31= 的 format 方法的注释]的DisplayFormatterclass:

If an object implement `_repr_mimebundle_` as well as various
`_repr_*_`, the data returned by `_repr_mimebundle_` will take
precedence and the corresponding `_repr_*_` for this mimetype will
not be called.

因此，格式化程序函数使用 get_real_method() 函数检查是否存在特定方法（参见 here), which calls getattr using a dummy method name that should not exist. In my case I had defined my class to have its own __getattr__ method (and this is where my problems arose), which used the hasattr function. Due to issues with hasattr discussed here 这会导致问题，在我的情况下，这意味着卡在 __getattr__ 函数中。因此，如果您定义自己的 __getattr__ 函数，请务必小心，因为它可能会产生意想不到的后果！

返回 ipython 中对象的实例时使用了哪些属性？

What attributes are used when returning an instance of the object in ipython?

ipython