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Learn Python: Classes
Everything is an Object

Attributes can be added to user-defined objects after instantiation, so it’s possible for an object to have some attributes that are not explicitly defined in an object’s constructor. We can use the dir() function to investigate an object’s attributes at runtime. dir() is short for directory and offers an organized presentation of object attributes.

class FakeDict: pass fake_dict = FakeDict() fake_dict.attribute = "Cool" dir(fake_dict) # Prints ['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__()', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'attribute']

That’s certainly a lot more attributes than we defined! Python automatically adds a number of attributes to all objects that get created. These internal attributes are usually indicated by double-underscores. But sure enough, attribute is in that list.

Do you remember being able to use type() on Python’s native data types? This is because they are also objects in Python. Their classes are int, float, str, list, and dict. These Python classes have special syntax for their instantiation, 1, 1.0, "hello", [], and {} specifically. But these instances are still full-blown objects to Python.

fun_list = [10, "string", {'abc': True}] type(fun_list) # Prints <class 'list'> dir(fun_list) # Prints ['__add__', '__class__', [...], 'append', 'clear', 'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']

Above we define a new list. We check it’s type and see that’s an instantiation of class list. We use dir() to explore its attributes, and it gives us a large number of internal Python dunder attributes, but, afterward, we get the usual list methods.

Instructions

1.

Call dir() on the number 5. Print out the results.

2.

Define a function called this_function_is_an_object. It can take any parameters and return anything you’d like.

3.

Print out the result of calling dir() on this_function_is_an_object.

Functions are objects too!

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