Python’s getattr function is used to fetch an attribute from
an object, using a string object instead of an identifier to identify the
attribute. In other words, the following two statements are equivalent:
value = obj.attribute
value = getattr(obj, "attribute")
If the attribute exists, the corresponding value is
returned. If the attribute does not exist, you get anAttributeError exception
instead.
The getattr function can be used on any object that supports
dotted notation (by implementing the__getattr__ method). This includes class
objects, modules, and even function objects.
path = getattr(sys, "path")
doc = getattr(len, "__doc__")
The getattr function uses the same lookup rules as ordinary
attribute access, and you can use it both with ordinary attributes and methods:
result = obj.method(args)
func = getattr(obj, "method")
result = func(args)
or, in one line:
result = getattr(obj, "method")(args)
Calling both getattr and the method on the same line can
make it hard to handle exceptions properly. To avoid confusing AttributeError
exceptions raised by getattr with similar exceptions raised inside the method,
you can use the following pattern:
try:
func =
getattr(obj, "method")
except AttributeError:
... deal with
missing method ...
else:
result =
func(args)
The function takes an optional default value, which is used
if the attribute doesn’t exist. The following example only calls the method if
it exists:
func = getattr(obj, "method", None)
if func:
func(args)
Here’s a variation, which checks that the attribute is
indeed a callable object before calling it.
func = getattr(obj, "method", None)
if callable(func):
func(args)
