Clarification about dir() in Python

https://docs.python.org/3/library/functions.html#dir said:

dir()
dir(object)

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

If the object has a method named __dir__(), this method will be called andmust return the list of attributes. This allows objects that implement a custom__getattr__() or __getattribute__() function to customize the waydir() reports their attributes.

If the object does not provide __dir__(), the function tries its best togather information from the object’s __dict__ attribute, if defined, andfrom its type object. The resulting list is not necessarily complete and maybe inaccurate when the object has a custom __getattr__().

The default dir() mechanism behaves differently with different types ofobjects, as it attempts to produce the most relevant, rather than complete, information:

• If the object is a module object, the list contains the names of the module’sattributes.
• If the object is a type or class object, the list contains the names of itsattributes, and recursively of the attributes of its bases.
• Otherwise, the list contains the object’s attributes’ names, the names of itsclass’s attributes, and recursively of the attributes of its class’s baseclasses.

The resulting list is sorted alphabetically. For example:

>>>
import struct

dir() # show the names in the module namespace
['__builtins__', '__name__', 'struct']

dir(struct) # show the names in the struct module
['Struct', '__all__', '__builtins__', '__cached__', '__doc__', '__file__',
'__initializing__', '__loader__', '__name__', '__package__',
'_clearcache', 'calcsize', 'error', 'pack', 'pack_into',
'unpack', 'unpack_from']

class Shape:

def __dir__(self):

return ['area', 'perimeter', 'location']

s = Shape()

dir(s)
['area', 'location', 'perimeter']Note
Because dir() is supplied primarily as a convenience for use at an interactive prompt, it tries to supply an interesting set of names more than it tries to supply a rigorously or consistently defined set of names, and its detailed behavior may change across releases. For example, metaclass attributes are not in the result list when the argument is a class.