python - Python 在实例化新类时返回什么？

Question

在实例化一个新类时，我发现 Python 有很多怪癖。我敢肯定这只是因为我不习惯这种语言，但即便如此，我看到的行为确实很奇怪。

如果我打开 iPython 并输入以下内容:

class Person:
    def __init__(self, name):
        self.name = name

    def hello(self):
        print "Hello, " + self.name

一切都如我所愿:

In [2]: Person
Out[2]: <class __main__.Person at 0x1c97330>

In [3]: p = Person("Jamie")

In [4]: p
Out[4]: <__main__.Person instance at 0x1c90b98>

In [5]: p.hello()
Hello, Jamie

但是，如果我随后访问包内的一个单独的类——没什么特别的，我可能会添加——并实例化一个新类，一切都会出错。 Here's the link to the code对于 palestrina/cache.py

In [6]: from palestrina.cache import Cache

In [7]: Cache
Out[7]: <class palestrina.cache.Cache at 0x1c97750>

In [8]: c = Cache(application = 'example', backend = 'filesystem')

In [9]: c
Out[9]: ---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)

/Users/jamierumbelow/Sites/Os/palestrina/<ipython console> in <module>()

/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/IPython/Prompts.pyc in __call__(self, arg)
    550 
    551             # and now call a possibly user-defined print mechanism

--> 552             manipulated_val = self.display(arg)
    553 
    554             # user display hooks can change the variable to be stored in


/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/IPython/Prompts.pyc in _display(self, arg)
    576             return IPython.generics.result_display(arg)
    577         except TryNext:
--> 578             return self.shell.hooks.result_display(arg)
    579 
    580     # Assign the default display method:


/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/IPython/hooks.pyc in __call__(self, *args, **kw)
    139             #print "prio",prio,"cmd",cmd #dbg

    140             try:
--> 141                 ret = cmd(*args, **kw)
    142                 return ret
    143             except ipapi.TryNext, exc:

/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/IPython/hooks.pyc in result_display(self, arg)
    169 
    170     if self.rc.pprint:
--> 171         out = pformat(arg)
    172         if '\n' in out:
    173             # So that multi-line strings line up with the left column of


/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/pprint.pyc in pformat(self, object)
    109     def pformat(self, object):
    110         sio = _StringIO()
--> 111         self._format(object, sio, 0, 0, {}, 0)
    112         return sio.getvalue()
    113 

/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/pprint.pyc in _format(self, object, stream, indent, allowance, context, level)
    127             self._readable = False
    128             return
--> 129         rep = self._repr(object, context, level - 1)
    130         typ = _type(object)
    131         sepLines = _len(rep) > (self._width - 1 - indent - allowance)

/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/pprint.pyc in _repr(self, object, context, level)
    221     def _repr(self, object, context, level):
    222         repr, readable, recursive = self.format(object, context.copy(),
--> 223                                                 self._depth, level)
    224         if not readable:
    225             self._readable = False

/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/pprint.pyc in format(self, object, context, maxlevels, level)
    233         and whether the object represents a recursive construct.
    234         """
--> 235         return _safe_repr(object, context, maxlevels, level)
    236 
    237 

/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/pprint.pyc in _safe_repr(object, context, maxlevels, level)
    318         return format % _commajoin(components), readable, recursive
    319 
--> 320     rep = repr(object)
    321     return rep, (rep and not rep.startswith('<')), False
    322

TypeError: 'bool' object is not callable

我不明白这里发生了什么。有人可以向我解释可能发生的情况吗？

谢谢。

Answer 1

好吧，您删除了相关部分(回溯)并在您的粘贴中将其替换为 ...。

但是看起来你在类的表示中有错误。

这是错误的模拟:

>>> class MyClass(object):
...     def __repr__(self):
...         return True()
...
>>> c = MyClass()
>>> c

请检查您删除的回溯，您会看到到底发生了什么。如果不能，请编辑您的问题并将其包括在内，以便我们进一步解释。

提供该类的源代码也会有所帮助。