Python dir() Built in Function

The dir() function in Python is used to get a list of attributes and methods of an object. The dir() function takes an object as an argument and returns a list of strings containing the names of its attributes and methods. The object can be any Python data type or user-defined class. Here are some examples of using dir() in Python:

Get all the attributes and methods of a built-in Python object:

 >>> dir(list)
['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__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']

Get all the variables and functions defined in a module:

import math
print(dir(math))

Output:

['__doc__', '__loader__', '__name__', '__package__', '__spec__', 'acos', 'acosh', 'asin', 'asinh', 'atan', 'atan2', 'atanh', 'ceil', 'comb', 'copysign', 'cos', 'cosh', 'degrees', 'dist', 'erf', 'erfc', 'exp', 'expm1', 'fabs', 'factorial', 'floor', 'fmod', 'frexp', 'fsum', 'gamma', 'gcd', 'hypot', 'inf', 'isclose', 'isfinite', 'isinf', 'isnan', 'isqrt', 'lcm', 'ldexp', 'lgamma', 'log', 'log10', 'log1p', 'log2', 'modf', 'nan', 'perm', 'pi', 'pow', 'prod', 'radians', 'remainder', 'sin', 'sinh', 'sqrt', 'tan', 'tanh', 'tau', 'trunc']

Get all the attributes and methods of a user-defined class:

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def say_hello(self):
        print("Hello, my name is", self.name)

p = Person("Alice", 30)
print(dir(p))

Output:

['__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__', 'age', 'name', 'say_hello']

As you can see, dir() is a very useful function for exploring the attributes and methods of different Python objects.

Some more examples:

# Use dir() with a string
s = "Hello"
result = dir(s)
print(result) # Output: ['__add__', '__class__', '__contains__', '__delattr__', '__dir__', '__doc__', ...]

# Use dir() with a list
l = [1, 2, 3]
result = dir(l)
print(result) # Output: ['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', '__dir__', ...]

# Use dir() with a user-defined class
class Student():
    def __init__(self, name):
        self.name = name

    def greet(self):
        print(f"Hello, {self.name}!")

stu = Student("Alice")
result = dir(stu)
print(result) # Output: ['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', ... 'greet', 'name']

If you have any questions about this code, you can drop a line in comment.

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