I want to override the __getattr__
method on a class to do something fancy but I don't want to break the default behavior.
What's the correct way to do this?
Overriding __getattr__
should be fine -- __getattr__
is only called as a last resort i.e. if there are no attributes in the instance that match the name. For instance, if you access foo.bar
, then __getattr__
will only be called if foo
has no attribute called bar
. If the attribute is one you don't want to handle, raise AttributeError
:
class Foo(object):
def __getattr__(self, name):
if some_predicate(name):
# ...
else:
# Default behaviour
raise AttributeError
However, unlike __getattr__
, __getattribute__
will be called first (only works for new style classes i.e. those that inherit from object). In this case, you can preserve default behaviour like so:
class Foo(object):
def __getattribute__(self, name):
if some_predicate(name):
# ...
else:
# Default behaviour
return object.__getattribute__(self, name)