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?

 

[Arnaud Delobelle]

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')

 

[Terry Reedy]

hasattr(a, 'attr1')

or
try: a.attr1
except AttributeError: pass

Terry Jan Reedy

 

[Jan Kaliszewski]

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