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。
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
除了这些答案之外,我还将包括一个函数(python 3),用于输出任何值的几乎整个结构。它使用dir来建立属性名的完整列表,然后对每个名称使用getattr。它会显示值的每个成员的类型,如果可能的话还会显示整个成员:
import json
def get_info(obj):
type_name = type(obj).__name__
print('Value is of type {}!'.format(type_name))
prop_names = dir(obj)
for prop_name in prop_names:
prop_val = getattr(obj, prop_name)
prop_val_type_name = type(prop_val).__name__
print('{} has property "{}" of type "{}"'.format(type_name, prop_name, prop_val_type_name))
try:
val_as_str = json.dumps([ prop_val ], indent=2)[1:-1]
print(' Here\'s the {} value: {}'.format(prop_name, val_as_str))
except:
pass
现在,以下任何一项都应该让你有所了解:
get_info(None)
get_info('hello')
import numpy
get_info(numpy)
# ... etc.
其他回答
获取对象的属性
class new_class():
def __init__(self, number):
self.multi = int(number) * 2
self.str = str(number)
new_object = new_class(2)
print(dir(new_object)) #total list attributes of new_object
attr_value = new_object.__dict__
print(attr_value) #Dictionary of attribute and value for new_class
for attr in attr_value: #attributes on new_class
print(attr)
输出
['__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']
{'multi': 4, 'str': '2'}
multi
str
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.
除了这些答案之外,我还将包括一个函数(python 3),用于输出任何值的几乎整个结构。它使用dir来建立属性名的完整列表,然后对每个名称使用getattr。它会显示值的每个成员的类型,如果可能的话还会显示整个成员:
import json
def get_info(obj):
type_name = type(obj).__name__
print('Value is of type {}!'.format(type_name))
prop_names = dir(obj)
for prop_name in prop_names:
prop_val = getattr(obj, prop_name)
prop_val_type_name = type(prop_val).__name__
print('{} has property "{}" of type "{}"'.format(type_name, prop_name, prop_val_type_name))
try:
val_as_str = json.dumps([ prop_val ], indent=2)[1:-1]
print(' Here\'s the {} value: {}'.format(prop_name, val_as_str))
except:
pass
现在,以下任何一项都应该让你有所了解:
get_info(None)
get_info('hello')
import numpy
get_info(numpy)
# ... etc.
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'}
人们经常提到,要列出一个完整的属性列表,应该使用dir()。但是请注意,与普遍观点相反,dir()并没有显示所有属性。例如,你可能会注意到__name__可能在类的dir()列表中缺失,即使你可以从类本身访问它。从dir()的文档(Python 2, Python 3):
因为提供dir()主要是为了方便在 交互式提示符,它试图提供一组有趣的名称 它不仅仅是试图提供一个严格或一致定义的集合 的名称,其详细行为可能在不同版本之间更改。为 属性时,元类属性不在结果列表中 参数是一个类。
像下面这样的函数往往更完整,尽管不能保证完整性,因为dir()返回的列表可能受到许多因素的影响,包括实现__dir__()方法,或在类或其父类之一上自定义__getattr__()或__getattribute__()。详情请参阅所提供的链接。
def dirmore(instance):
visible = dir(instance)
visible += [a for a in set(dir(type)).difference(visible)
if hasattr(instance, a)]
return sorted(visible)