Styjun

I know how to iterate through the attributes of an object. But that excludes attributes realized through getters/setters or @property decorators.

How can I iterate through those?

class MyClass:

 def __init__(self):
 self.foo = "bar"

 @property
 def myprop(self):
 return "hello"


my_instance = MyClass()

for i in my_instance.__dict__:
 print("object has attribute %s" % i)

This little script prints:

object has attribute foo

What I want though is a script that prints:

object has attribute foo
object has attribute myprop

You can use dir() to get all the attributes, though that will include methods inherited from base classes, including all the dunder methods from object:

class MyClass:

 def __init__(self):
 self.foo = "bar"

 @property
 def myprop(self):
 return "hello"


my_instance = MyClass()

for i in dir(my_instance):
 print("object has attribute %s" % i)

prints:

object has attribute __class__
object has attribute __delattr__
object has attribute __dict__
object has attribute __dir__
object has attribute __doc__
object has attribute __eq__
object has attribute __format__
object has attribute __ge__
object has attribute __getattribute__
object has attribute __gt__
object has attribute __hash__
object has attribute __init__
object has attribute __init_subclass__
object has attribute __le__
object has attribute __lt__
object has attribute __module__
object has attribute __ne__
object has attribute __new__
object has attribute __reduce__
object has attribute __reduce_ex__
object has attribute __repr__
object has attribute __setattr__
object has attribute __sizeof__
object has attribute __str__
object has attribute __subclasshook__
object has attribute __weakref__
object has attribute foo
object has attribute myprop

You can exclude some with string operations:

for i in dir(my_instance):
 if i.startswith("__"):
 continue
 print("object has attribute %s" % i)

prints:

object has attribute foo
object has attribute myprop

You can look for the property instances in the object class:

def get_properties(obj):
 cls = type(obj)
 props = 
 for k in dir(cls):
 attr = getattr(cls, k)
 # Check that it is a property with a getter
 if isinstance(attr, property) and attr.fget:
 val = attr.fget(obj)
 props[k] = attr.fget(obj)
 return props

class A(object):
 def __init__(self, p):
 self._p = p
 @property
 def p(self):
 return self._p
 p2 = property(fget=lambda self: 2 * self._p)

a = A(1)
a_props = get_properties(a)
print(a_props)
# 'p': 1, 'p2': 2