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

[thinke365]

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?

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[Arnaud Delobelle]

thinke365 <thin...@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')

--
Arnaud

[Terry Reedy]

or
try: a.attr1
except AttributeError: pass

Terry Jan Reedy

[Jan Kaliszewski]

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

> On 1/23/2010 10:56 AM, Arnaud Delobelle wrote:

> 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) <z...@chopin.edu.pl>