Function Name:
dir
Function Signature:
dir([object])
Function Overview:
- The dir() function returns a list of attributes of an object. The list returned may not be the complete list of attributes.
- If the parameter 'object' is omitted, dir() returns the list of names in the current scope.
- Every object in Python has '0' to 'n' number of attributes defined for it, by the developer.
- Apart from the attributes defined be the developers, every python object also has several special attributes that are defined by the implementation as relevant to the object.
- The dir() function returns the special attributes of the object as well – however not all the special attributes are returned by the dir() function.
- If an object has the __dir__() method implemented, the attributes are returned as per the iterable returned by the __dir__() method.
- Python allows instance attributes to be computed and returned from special functions __getattr__() and __getattribute__() as well. The implementation of __dir__() must return the list of attributes in accordance with the __getattr__() and __getattribute__().
Example 1 – Without __dir__() being overridden:
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class Student: def __init__(self, firstName, lastName, id): self.firstName = firstName self.lastName = lastName self.id = id
def __dir__(self): return (self.id,)
s1 = Student("John", "Adams", "01") print(dir(s1)) |
Output:
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['__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__', 'firstName', 'id', 'lastName'] |
In the above output python defined attributes for the object s1 are listed by the dir() function followed by the developer defined attributes – firstName, id and lastName.
Example 2 – With __dir__() being overridden:
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class Student: def __init__(self, firstName, lastName, id): self.firstName = firstName self.lastName = lastName self.id = id
def __dir__(self): return self.__dict__.keys()
s1 = Student("John", "Adams", "01") print(dir(s1)) |
Output:
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['firstName', 'id', 'lastName'] |