问题:如何在Python中枚举对象的属性?
IC#我们通过反思来做到。在Javascript中,它很简单:
for(var propertyName in objectName)
var currentPropertyValue = objectName[propertyName];
如何在Python中完成?
I C# we do it through reflection. In Javascript it is simple as:
for(var propertyName in objectName)
var currentPropertyValue = objectName[propertyName];
How to do it in Python?
回答 0
for property, value in vars(theObject).iteritems():
print property, ": ", value
请注意,在极少数情况下,有一个__slots__
属性,此类通常没有属性__dict__
。
for property, value in vars(theObject).items():
print(property, ":", value)
Be aware that in some rare cases there’s a __slots__
property, such classes often have no __dict__
.
回答 1
请参阅inspect.getmembers(object[, predicate])
。
返回按名称排序的(名称,值)对列表中的对象的所有成员。如果提供了可选的谓词参数,则仅包含谓词为其返回真值的成员。
>>> [name for name,thing in inspect.getmembers([])]
['__add__', '__class__', '__contains__', '__delattr__', '__delitem__',
'__delslice__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__',
'__getitem__', '__getslice__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__iter__',
'__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__','__reduce_ex__',
'__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', '__setslice__',
'__sizeof__', '__str__', '__subclasshook__', 'append', 'count', 'extend', 'index',
'insert', 'pop', 'remove', 'reverse', 'sort']
>>>
See inspect.getmembers(object[, predicate])
.
Return all the members of an object in a list of (name, value) pairs sorted by name. If the optional predicate argument is supplied, only members for which the predicate returns a true value are included.
>>> [name for name,thing in inspect.getmembers([])]
['__add__', '__class__', '__contains__', '__delattr__', '__delitem__',
'__delslice__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__',
'__getitem__', '__getslice__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__iter__',
'__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__','__reduce_ex__',
'__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', '__setslice__',
'__sizeof__', '__str__', '__subclasshook__', 'append', 'count', 'extend', 'index',
'insert', 'pop', 'remove', 'reverse', 'sort']
>>>
回答 2
回答 3
__dict__
对象的属性是其所有其他定义的属性的字典。请注意,Python类可以覆盖getattr
并使内容看起来像属性,而不是in __dict__
。还有一些内置函数vars()
,dir()
它们在微妙的方式上有所不同。并且__slots__
可以代替__dict__
一些不寻常的类。
Python中的对象很复杂。__dict__
是开始进行反射式编程的正确位置。dir()
如果您是在交互式shell中四处乱逛,那么这是一个开始的地方。
The __dict__
property of the object is a dictionary of all its other defined properties. Note that Python classes can override getattr
and make things that look like properties but are not in__dict__
. There’s also the builtin functions vars()
and dir()
which are different in subtle ways. And __slots__
can replace __dict__
in some unusual classes.
Objects are complicated in Python. __dict__
is the right place to start for reflection-style programming. dir()
is the place to start if you’re hacking around in an interactive shell.
回答 4
georg scholly短版
print vars(theObject)
for one-liners:
print vars(theObject)
回答 5
如果您正在寻找所有属性的反映,那么上面的答案很好。
如果您只是想获取字典的键(与Python中的“对象”不同),请使用
my_dict.keys()
my_dict = {'abc': {}, 'def': 12, 'ghi': 'string' }
my_dict.keys()
> ['abc', 'def', 'ghi']
If you’re looking for reflection of all properties, the answers above are great.
If you’re simply looking to get the keys of a dictionary (which is different from an ‘object’ in Python), use
my_dict.keys()
my_dict = {'abc': {}, 'def': 12, 'ghi': 'string' }
my_dict.keys()
> ['abc', 'def', 'ghi']
回答 6
其他答案完全涵盖了这一点,但我将使其明确。对象可以具有类属性以及静态和动态实例属性。
class foo:
classy = 1
@property
def dyno(self):
return 1
def __init__(self):
self.stasis = 2
def fx(self):
return 3
stasis
是静态的,dyno
是动态的(请参阅属性装饰器),并且classy
是类属性。如果我们简单地做,__dict__
否则vars
我们只会得到静态的。
o = foo()
print(o.__dict__) #{'stasis': 2}
print(vars(o)) #{'stasis': 2}
因此,如果我们希望其他人__dict__
都能得到一切(甚至更多)。这包括魔术方法和属性以及法线绑定方法。因此,请避免这些情况:
d = {k: getattr(o, k, '') for k in o.__dir__() if k[:2] != '__' and type(getattr(o, k, '')).__name__ != 'method'}
print(d) #{'stasis': 2, 'classy': 1, 'dyno': 1}
type
具有属性修饰方法(动态属性)的调用将为您提供返回值的类型,而不是method
。为了证明这一点,让我们用json将其字符串化:
import json
print(json.dumps(d)) #{"stasis": 2, "classy": 1, "dyno": 1}
如果这是一种方法,它将崩溃。
TL; DR。尝试同时调用extravar = lambda o: {k: getattr(o, k, '') for k in o.__dir__() if k[:2] != '__' and type(getattr(o, k, '')).__name__ != 'method'}
这三个方法,但不要调用方法或魔术。
This is totally covered by the other answers, but I’ll make it explicit.
An object may have class attributes and static and dynamic instance attributes.
class foo:
classy = 1
@property
def dyno(self):
return 1
def __init__(self):
self.stasis = 2
def fx(self):
return 3
stasis
is static, dyno
is dynamic (cf. property decorator) and classy
is a class attribute. If we simply do __dict__
or vars
we will only get the static one.
o = foo()
print(o.__dict__) #{'stasis': 2}
print(vars(o)) #{'stasis': 2}
So if we want the others __dict__
will get everything (and more).
This includes magic methods and attributes and normal bound methods. So lets avoid those:
d = {k: getattr(o, k, '') for k in o.__dir__() if k[:2] != '__' and type(getattr(o, k, '')).__name__ != 'method'}
print(d) #{'stasis': 2, 'classy': 1, 'dyno': 1}
The type
called with a property decorated method (a dynamic attribute) will give you the type of the returned value, not method
. To prove this let’s json stringify it:
import json
print(json.dumps(d)) #{"stasis": 2, "classy": 1, "dyno": 1}
Had it been a method it would have crashed.
TL;DR. try calling extravar = lambda o: {k: getattr(o, k, '') for k in o.__dir__() if k[:2] != '__' and type(getattr(o, k, '')).__name__ != 'method'}
for all three, but not methods nor magic.