[python] Explain __dict__ attribute

I am really confused about the __dict__ attribute. I have searched a lot but still I am not sure about the output.

Could someone explain the use of this attribute from zero, in cases when it is used in a object, a class, or a function?

Basically it contains all the attributes which describe the object in question. It can be used to alter or read the attributes. Quoting from the documentation for __dict__

A dictionary or other mapping object used to store an object's (writable) attributes.

Remember, everything is an object in Python. When I say everything, I mean everything like functions, classes, objects etc (Ya you read it right, classes. Classes are also objects). For example:

def func():
    pass

func.temp = 1

print(func.__dict__)

class TempClass:
    a = 1
    def temp_function(self):
        pass

print(TempClass.__dict__)

will output

{'temp': 1}
{'__module__': '__main__', 
 'a': 1, 
 'temp_function': <function TempClass.temp_function at 0x10a3a2950>, 
 '__dict__': <attribute '__dict__' of 'TempClass' objects>, 
 '__weakref__': <attribute '__weakref__' of 'TempClass' objects>, 
 '__doc__': None}