How to know if an object has an attribute in Python?

Python is an object-oriented programming language, here attributes are known as properties of an object. By using different methods, we can check if an object has an attribute or not.

To check if an object contains a particular attribute then we can use hasattr() method and getattr() method. Or if we want to get all existing attributes then we can use the dir() method. (Learn more about Python directories: Python Directories Tutorial)

Initially create a dummy Python class with two attributes then assign it to an object, and it will refer throughout this article.

class DummyClass():
    var1 = 'Value1'
    var2 = 2

obj = DummyClass()

Accessing attributes directly

In this example we try to access the attribute of an object directly, here we might get an AttributeError if the attribute doesn't exist. If we don't get an AttributeError, then will know the object has the attribute.

Example

For the above example the object does not contain the attribute "a", and it contains "var1", "var2" attributes.

class DummyClass():
    var1 = 'Value1'
    var2 = 2

obj = DummyClass()
print(obj.var1)
print(obj.var2)
print(obj.a)

Output

Value1
2
Traceback (most recent call last):
  File "/home/cg/root/57371/main.py", line 8, in 
    print(obj.a)
AttributeError: 'DummyClass' object has no attribute 'a'

Accessing attributes using the getattr() method

Same as direct attributes accessing like the above example the getattr() method also returns the value of the named attribute (if it exists), and returns AttributeError if the attribute doesn’t exist.

Syntax

getattr(object, name[, default])

This function has three parameters, the name of the object whose attributes have to be found, name which attribute we want to check, and finally [, default] it accepts a default argument which will be printed if the attribute does not exist instead of generating the AttributeError.

Example

The getattr() method returns the values of the existing attributes and throws the default arguments or AttributeError for the nonexistent attributes.

print(getattr(obj, 'var1', 'Attribute doesn't exist'))
print(getattr(obj, 'var2', 'Attribute doesn't exist'))
print(getattr(obj, 'a', 'Attribute doesn't exist'))
print(getattr(obj, 'a'))

Output

Value1
2
Attribute doesn't exist
Traceback (most recent call last):
  File "/home/cg/root/17209/main.py", line 9, in 
    print(getattr(obj, 'a'))
AttributeError: 'DummyClass' object has no attribute 'a'

Accessing attributes using the hasattr() method

The hasattr() method checks if an object has a specific attribute or not. The hasattr() method is implemented by using the getattr() method.

Syntax

hasattr(object, name )

This function has two parameters, the name of the object and attribute name, which we want to check. And returns a Boolean (True/False). It returns 'True' if the attribute is present in that object otherwise it will return 'False'.

Example

The obj method does not contains the "a" attribute so that it returns False. And for var1, var2 attributes it returns True as output.

class DummyClass():
    var1 = 'Value1'
    var2 = 2

obj = DummyClass()   
print(hasattr(obj, 'var1'))
print(hasattr(obj, 'var2'))
print(hasattr(obj, 'a'))

Output

True
True
False

Accessing all existing attributes by using the dir() method

The dir() method returns a list which contains all attributes of the object, also it will return the keys included in the __dict__ attribute.

Syntax

dir(object)

For some objects the dir() results may not be accurate, because the functionality might be modified using __getattr__ method.

Example

The dir() method returns the list of all existing attributes.

class DummyClass():
    var1 = 'Value1'
    var2 = 2

obj = DummyClass()   
print(dir(obj))

Output

['__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__', 'var1', 'var2']