Question

IPython源代码包括a getattr check，用于测试'_ipython_canary_method_should_not_exist_'函数开头是否存在get_real_method：

def get_real_method(obj, name):
    """Like getattr, but with a few extra sanity checks:
    - If obj is a class, ignore everything except class methods
    - Check if obj is a proxy that claims to have all attributes
    - Catch attribute access failing with any exception
    - Check that the attribute is a callable object
    Returns the method or None.
    """
    try:
        canary = getattr(obj, '_ipython_canary_method_should_not_exist_', None)
    except Exception:
        return None

    if canary is not None:
        # It claimed to have an attribute it should never have
        return None

尽管find其他编码员特别容易使用此名称，但是很容易找到有关原因的任何有意义的解释。

鉴于这两个类：

from __future__ import print_function

class Parrot(object):
    def __getattr__(self, attr):
        print(attr)
        return lambda *a, **kw: print(attr, a, kw)

class DeadParrot(object):
    def __getattr__(self, attr):
        print(attr)
        if attr == '_ipython_canary_method_should_not_exist_':
            raise AttributeError(attr)
        return lambda *a, **kw: print(attr, a, kw)

似乎IPython正在使用此方法的存在与否来决定是使用repr还是使用rich display methods之一。故意阻止DeadParrot中的测试会导致IPython查找并调用_repr_mimebundle_。

我正在写一个假装所有attrs存在的对象。我如何决定是否特殊情况？

IPython“Canary Method”的含义以及如果它存在会发生什么？

0 个答案: