Lucas G. Sánchez Lucas G. Sánchez - 11 months ago 48
Python Question

How to know if an object has an attribute in Python

Is there a way in Python to determine if an object has some attribute? For example:

>>> a = SomeClass()
>>> a.someProperty = value
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: SomeClass instance has no attribute 'property'

How can you tell if
has the attribute
before using it?

Answer Source

Try hasattr():

if hasattr(a, 'property'):

EDIT: See zweiterlinde's answer below, who offers good advice about asking forgiveness! A very pythonic approach!

The general practice in python is that, if the property is likely to be there most of the time, simply call it and either let the exception propagate, or trap it with a try/except block. This will likely be faster than hasattr. If the property is likely to not be there most of the time, or you're not sure, using hasattr will probably be faster than repeatedly falling into an exception block.