__dir__() is a built-in function in Python that returns a list of names in the current local scope or an object's attributes, depending on the context in which it is called.

When __dir__() is called without any arguments, it returns a list of names of the attributes and methods in the current local scope. For example:

print(__dir__())  

This will print a list of names in the current local scope, including built-in names, global names, and names defined in the current module.

When __dir__() is called on an object, it returns a list of valid attributes and methods that can be accessed on that object. For example:

my_list = [1, 2, 3]  
print(my_list.__dir__())  

This will print a list of attributes and methods that can be used on the my_list object, such as append(), count(), and sort().

Note that __dir__() is typically called implicitly when using the dir() function. For example:

print(dir(my_list))  

This will have the same effect as calling my_list.__dir__().