python __str__(),__dir__(),__doc__

对于一个类的属性查看，用dir

__str__() 是介绍这个类的信息

__doc__ 这个是文档字符串，也是介绍

对于dir的用法

>>> import os>>> try:...     a = 1/0... except Exception,reason1:...     print "can't /"...can't />>> print reason1integer division or modulo by zero>>> print reason1.__str__()integer division or modulo by zero>>> dir(reason1)['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__getitem__', '__getslice__', '__hash__', '__init__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__setstate__', '__sizeof__', '__str__', '__subclasshook__', '__unicode__', 'args', 'message']>>> print reason1.__doc__()Traceback (most recent call last):  File "<stdin>", line 1, in <module>TypeError: 'str' object is not callable>>> print reason1.__doc__Second argument to a division or modulo operation was zero.>>> print reason1.__str__<method-wrapper '__str__' of exceptions.ZeroDivisionError object at 0x10c095b90>>>> print reason1.__calss__Traceback (most recent call last):  File "<stdin>", line 1, in <module>AttributeError: 'exceptions.ZeroDivisionError' object has no attribute '__calss__'>>> print reason1.__class__<type 'exceptions.ZeroDivisionError'>>>> type(reason1.__doc__)<type 'str'>>>>

对于dir，它显示的是类的所有的属性和方法。

中文说明：不带参数时，返回当前范围内的变量、方法和定义的类型列表；带参数时，返回参数的属性、方法列表。

如果参数包含方法__dir__(),该方法被调用。如果参数不包含__dir__(),该方法将最大限度地收集参数信息。