Python dir() built-in function

The dir() function in Python is a powerful built-in function that returns a list of names in the current namespace or the attributes of a given object. It’s commonly used to introspect and explore objects, modules, and classes, helping you discover the available methods, attributes, and names that you can work with.

From the Python 3 documentation

Without arguments, return the list of names in the current local scope. With an argument, attempt to return a list of valid attributes for that object.

Syntax

dir([object])

object (optional): The object whose attributes you want to explore. If not provided, it returns the names in the current namespace.

Exploring Names in the Current Namespace

a = 10
b = "Hello"
def my_function():
    pass

print(dir())
# Output: ['__annotations__', '__builtins__', '__doc__', '__loader__', '__name__', '__package__', '__spec__', 'a', 'b', 'my_function']

Exploring Module Attributes

import math
print(dir(math))
# Output: ['__doc__', '__loader__', '__name__', '__package__', '__spec__', 'acos', 'acosh', 'asin', ... ]

Exploring Object Attributes

class MyClass:
    def __init__(self):
        self.x = 5
        self.y = "Hello"

obj = MyClass()
print(dir(obj))
# Output: ['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', ... 'x', 'y']

Using `dir()` with Built-in Types

my_list = [1, 2, 3]
print(dir(my_list))
# Output: [..., 'append', 'clear', 'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']

Filtering `dir()` Output

import math
print([name for name in dir(math) if not name.startswith("__")])
# Output: ['acos', 'acosh', 'asin', 'asinh', 'atan', 'atan2', ... ]