CODEWITHSUNDEEP
pythonclassproperties
Addman
Addman

Reputation: 341

Get the list of 'property' class attributes of a class in python

Dear Stackoverflow community,

I am trying to get a list of properties in my class. So far I have this:

class A(object):

    def __init__(self):
        self._val = 0

    @property
    def val(self):
        return self._val

    @val.setter
    def val(self, val):
        """
        +1 just as a lazy check if the method is invoked
        """
        self._val = val + 1

    def get_props(self):
        return [ str(x) for x in dir(self)
                if isinstance( getattr(self, x), property ) ]

if __name__ == "__main__":

    import sys

    print("Python version")
    print (sys.version)
    print("Version info.")
    print (sys.version_info)
    print()

    a = A()
    print(f"Before asigment: {a.val}")
    a.val = 19
    print(f"After asigment: {a.val}")
    print(f"My properties: {a.get_props()}")
    print(f"The type of the attribute 'val' is {type(getattr(a, 'val'))}")

According to this Q/A it should work. However, my result is:

Python version
3.7.3 (default, Jul 25 2020, 13:03:44) 
[GCC 8.3.0]
Version info.
sys.version_info(major=3, minor=7, micro=3, releaselevel='final', serial=0)

Before asigment: 0
After asigment: 20
My properties: []
The type of the attribute 'val' is <class 'int'>

I'm trying to avoid importing new modules (like inspect). What am I missing?

Thank you!

Upvotes: 0

Views: 1631

Answers (1)

Jasmijn
Jasmijn

Reputation: 10452

propertys are defined on the class, if you try to access them via an instance, their __get__ is called. So make it a class method instead:

    @classmethod
    def get_props(cls):
        return [x for x in dir(cls)
                if isinstance( getattr(cls, x), property) ]

Upvotes: 5

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