Python dir() usage and example

Python built-in functions

dir() method attempts to return a list of valid attribute lists of the object.

The syntax of dir() is:

dir([object])

dir() parameters

dir() can contain at most one object.

• Object(Optional)-dir() attempts to return all attributes of this object.

dir() return value

dir() attempts to return a list of valid attributes of the object.

• If the object has a __dir__() method, that method is called, and it must return a list of attributes.

• If the object does not have a __dir__() method, this method attempts to find information from the __dict__ attribute (if defined) and the type object. In this case, the list returned from dir() may be incomplete.

If an object is not passed to the dir() method, it will return a list of names in the current local scope.

Example1How does dir() work?

number = [1,　2,　3]
print(dir(number))
print('\nReturn Value from empty dir()')
print(dir())

When running the program, the output is:

__add__, __class__, __contains__, __delattr__, __delitem__, __dir__, __doc__, __eq__, __format__, __ge__, __getattribute__, __getitem__, __gt__, __hash__, __iadd__, __imul__, __init__, __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
Return Value from Empty dir()
__builtins__, number

Example2: dir() on user-defined objects

class Person:
　　def __dir__(self):
　　　　return ['age', 'name', 'salary']
　　　　
teacher = Person()
print(dir(teacher))

When running the program, the output is:

['age', 'name', 'salary']

Python built-in functions