是否有一种方法可以获取类实例上存在的属性列表?
class new_class():
def __init__(self, number):
self.multi = int(number) * 2
self.str = str(number)
a = new_class(2)
print(', '.join(a.SOMETHING))
期望的结果是输出"multi, str"。我希望它能看到脚本各个部分的当前属性。
当前回答
你要这个干什么?如果不知道你的确切意图，可能很难得到最好的答案。
It is almost always better to do this manually if you want to display an instance of your class in a specific way. This will include exactly what you want and not include what you don't want, and the order will be predictable. If you are looking for a way to display the content of a class, manually format the attributes you care about and provide this as the __str__ or __repr__ method for your class. If you want to learn about what methods and such exist for an object to understand how it works, use help. help(a) will show you a formatted output about the object's class based on its docstrings. dir exists for programatically getting all the attributes of an object. (Accessing __dict__ does something I would group as the same but that I wouldn't use myself.) However, this may not include things you want and it may include things you do not want. It is unreliable and people think they want it a lot more often than they do. On a somewhat orthogonal note, there is very little support for Python 3 at the current time. If you are interested in writing real software you are going to want third-party stuff like numpy, lxml, Twisted, PIL, or any number of web frameworks that do not yet support Python 3 and do not have plans to any time too soon. The differences between 2.6 and the 3.x branch are small, but the difference in library support is huge.
其他回答
上面所有的答案都是正确的，你有三个选项可以选择
dir () vars () __dict__
>>> dir(a)
['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'multi', 'str']
>>> vars(a)
{'multi': 4, 'str': '2'}
>>> a.__dict__
{'multi': 4, 'str': '2'}
>>> ', '.join(i for i in dir(a) if not i.startswith('__'))
'multi, str'
这当然会打印类定义中的任何方法或属性。你可以通过将i.startwith('__')更改为i.startwith('_')来排除“私有”方法。
__attrs__给出了一个实例的属性列表。
>>> import requests
>>> r=requests.get('http://www.google.com')
>>> r.__attrs__
['_content', 'status_code', 'headers', 'url', 'history', 'encoding', 'reason', 'cookies', 'elapsed', 'request']
>>> r.url
'http://www.google.com/'
>>>
attributes_list = [attribute for attribute in dir(obj) if attribute[0].islower()]
dir(instance)
# or (same value)
instance.__dir__()
# or
instance.__dict__
然后可以用type()测试类型是什么，或者用callable()测试是否为方法。
