Python: retrieve all properties of a class instance that uses the @property annotation

Question

Is there an easy way to retrieve all properties of a class instance that use @property or property methods?

I have seen examples that use vars but that does not work a class like:

class Test(object):
   CONSTANT='SKIP ME'

   def __init__(self):
       self.my = "my"
       self.__wrapper = {Test.CONSTANT : "wrapped value"}

   @property
   def wrapped_value(self):
       return self.__wrapper[Test.CONSTANT]

Desired output would be dictionary with key/value.

dict = {"my":  "my", 
        "wrapped_value": "wrapped value",
        "__wrapper" : <dict>
}

As an added plus is there a way to get it to skip class level variables?

Answer 1

A simple solution would be this:

instance = Test()
dict((p, getattr(instance, p))
     for p in dir(instance)
     if p not in dir(Test) or isinstance(getattr(Test, p), property))

It yields:

{'_Test__wrapper': {'SKIP ME': 'wrapped value'}, 'wrapped_value': 'wrapped value', 'my': 'my'}

Answer 2

property is a class. Just test the class members to see if they're an instance of it.

>>> class Foo(object):
...   @property
...   def bar(self):
...     return self._bar
... 
>>> [x for x in Foo.__dict__ if isinstance(Foo.__dict__[x], property)]
['bar']
>>> foo = Foo()
>>> [x for x in foo.__class__.__dict__ if isinstance(foo.__class__.__dict__[x], property)]
['bar']
>>> dict((x, getattr(foo, x)) for x in foo.__class__.__dict__ if isinstance(foo.__class__.__dict__[x], property))
{'bar': 42}

Answer 3

This will result in a dictionary of all properties of a class instance that use @property or property methods. It's similar to what others have said.

a = Test()
propdict = {} # or propdict = dict()

for attrname in dir(a.__class__):
     if isinstance(getattr(a.__class__, attrname), property):
         propdict[attrname] = getattr(a, attrname)

Then propdict would be {'wrapped_value': 'wrapped value'}, as wrapped_value is the only property of your Test class.