dir() function in Python

The dir() function is a built-in Python tool used to list the attributes (like methods, variables, etc.) of an object. It helps inspect modules, classes, functions, and even user-defined objects during development and debugging.

Syntax

dir([object])

Parameters: 

• object (optional): Any Python object (like list, dict, class, module, etc.)

Return Type: A list of names (strings) representing the attributes of the object or current scope.

Behavior

• Without arguments: Lists names in the current local scope.
• With modules: Lists all available functions, classes, and constants.
• With user-defined objects: Lists all attributes, including user-defined ones (if __dir__ is defined).
• With built-in objects: Lists all valid attributes and methods.

Examples dir() Function

Example 1: No Parameters Passed

In this example, we are using the dir() function to list object attributes and methods in Python. It provides a demonstration for exploring the available functions and objects in our Python environment.

Output:

['__annotations__', '__builtins__', '__doc__', '__loader__', '__name__', '__package__', '__spec__', 'traceback']

['__annotations__', '__builtins__', '__doc__', '__loader__', '__name__', '__package__', '__spec__', 'math', 'random', 'traceback']

Explanation:

• dir() lists names in the current local scope.
• Notice that after importing modules, the list includes random, math, etc, which were not present before importing them.

Example 2: Module Object Passed

This example demonstrates how dir() can explore all the attributes inside a module like random.

Output:

Attributes in random module:

['BPF', 'LOG4', 'NV_MAGICCONST', 'RECIP_BPF', 'Random', 'SG_MAGICCONST', 'SystemRandom', 'TWOPI', '_ONE', '_Sequence', '__all__', '__builtins__', '__cached__', '__doc__', '__file__', '__loader__', '__name__', '__package__', '__spec__', '_accumulate', '_acos', '_bisect', '_ceil', '_cos', '_e', '_exp', '_fabs', '_floor', '_index', '_inst', '_isfinite', '_lgamma', '_log', '_log2', '_os', '_pi', '_random', '_repeat', '_sha512', '_sin', '_sqrt', '_test', '_test_generator', '_urandom', '_warn', 'betavariate', 'binomialvariate', 'choice', 'choices', 'expovariate', 'gammavariate', 'gauss', 'getrandbits', 'getstate', 'lognormvariate', 'normalvariate', 'paretovariate', 'randbytes', 'randint', 'random', 'randrange', 'sample', 'seed', 'setstate', 'shuffle', 'triangular', 'uniform', 'vonmisesvariate', 'weibullvariate']

Explanation: Passing random lists all constants, functions, and classes available in the module

Example 3. When a List Object is Passed as Parameter

Here, we pass a list and a dictionary to dir() to explore their available methods.

Output:

['__add__', '__class__', '__class_getitem__', '__contains__', '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getstate__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', 'append', 'clear', 'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']
['__class__', '__class_getitem__', '__contains__', '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getstate__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__ior__', '__iter__', '__le__', '__len__', '__lt__', '__ne__', '__new__', '__or__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__ror__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', 'clear', 'copy', 'fromkeys', 'get', 'items', 'keys', 'pop', 'popitem', 'setdefault', 'update', 'values']

Explanation:

• dir(my_list) returns all methods available to a list (e.g., append, sort, etc.)
• dir(my_dict) returns methods for dictionaries (e.g., keys, values, etc.)

Example 4. When User Defined Objects are Passed as Parameters

You can define your own class and customize what dir() returns using the __dir__() method.

['item', 'price', 'quantity']

Explanation:

• Cart class defines a custom __dir__() method.
• dir(c) returns the list defined inside __dir__.

Also Read: __dir__(), objects.