how can i know if a python object have a attribute such as 'attr1'?

[Jan Kaliszewski]

24-01-2010, 00:38:29 Terry Reedy <tjreedy at udel.edu> wrote:

> On 1/23/2010 10:56 AM, Arnaud Delobelle wrote:
>> thinke365<thinke365 at gmail.com>  writes:
>>
>>> for example, i may define a python class:
>>> class A:
>>>       def sayHello():
>>>            print 'hello'
>>>
>>> a = A()
>>> a.attr1 = 'hello'
>>> a.attr2 = 'bb'
>>>
>>> b = A()
>>> a.attr2 = 'aa'
>>>
>>> how can i know whether an object have an attribute named attr1?
>>
>> hasattr(a, 'attr1')
>
> or
> try: a.attr1
> except AttributeError: pass

or

-- if you are interested only in attributes contained by attributes dict
of this particular object (and no in attributes of its type, base types
nor attributes calculated on-demand by __getattr__/__getattribute__
methods) --

you can check its __dict__ --
* using vars(), e.g.: if 'attr1' in vars(a)...
* or directly (less elegant?), e.g.: if 'attr1' in a.__dict__...

But please remember that it doesn't work for instances of types with
__slots__ defined (see:
http://docs.python.org/reference/datamodel.html#slots).

Regards,
*j

-- 
Jan Kaliszewski (zuo) <zuo at chopin.edu.pl>