Yes. Instead of passing in the instance attribute at class definition time, check it at runtime:
def check_authorization(f):
def wrapper(*args):
print args[0].url
return f(*args)
return wrapper
class Client(object):
def __init__(self, url):
self.url = url
@check_authorization
def get(self):
print 'get'
>>> Client('http://www.google.com').get()
http://www.google.com
get
The decorator intercepts the method arguments; the first argument is the instance, so it reads the attribute off of that. You can pass in the attribute name as a string to the decorator and use getattr
if you don't want to hardcode the attribute name:
def check_authorization(attribute):
def _check_authorization(f):
def wrapper(self, *args):
print getattr(self, attribute)
return f(self, *args)
return wrapper
return _check_authorization
A more concise example might be as follows:
#/usr/bin/env python3
from functools import wraps
def wrapper(method):
@wraps(method)
def _impl(self, *method_args, **method_kwargs):
method_output = method(self, *method_args, **method_kwargs)
return method_output + "!"
return _impl
class Foo:
@wrapper
def bar(self, word):
return word
f = Foo()
result = f.bar("kitty")
print(result)
Which will print:
kitty!
from re import search
from functools import wraps
def is_match(_lambda, pattern):
def wrapper(f):
@wraps(f)
def wrapped(self, *f_args, **f_kwargs):
if callable(_lambda) and search(pattern, (_lambda(self) or '')):
f(self, *f_args, **f_kwargs)
return wrapped
return wrapper
class MyTest(object):
def __init__(self):
self.name = 'foo'
self.surname = 'bar'
@is_match(lambda x: x.name, 'foo')
@is_match(lambda x: x.surname, 'foo')
def my_rule(self):
print 'my_rule : ok'
@is_match(lambda x: x.name, 'foo')
@is_match(lambda x: x.surname, 'bar')
def my_rule2(self):
print 'my_rule2 : ok'
test = MyTest()
test.my_rule()
test.my_rule2()
ouput: my_rule2 : ok
Another option would be to abandon the syntactic sugar and decorate in the __init__
of the class.
def countdown(number):
def countdown_decorator(func):
def func_wrapper():
for index in reversed(range(1, number+1)):
print(index)
func()
return func_wrapper
return countdown_decorator
class MySuperClass():
def __init__(self, number):
self.number = number
self.do_thing = countdown(number)(self.do_thing)
def do_thing(self):
print('im doing stuff!')
myclass = MySuperClass(3)
myclass.do_thing()
which would print
3
2
1
im doing stuff!
You can't. There's no self
in the class body, because no instance exists. You'd need to pass it, say, a str
containing the attribute name to lookup on the instance, which the returned function can then do, or use a different method entirely.
I know this is an old question, but this solution has not been mentioned yet, hopefully it may help someone even today, after 8 years.
So, what about wrapping a wrapper? Let's assume one cannot change the decorator neither decorate those methods in init (they may be @property decorated or whatever). There is always a possibility to create custom, class-specific decorator that will capture self and subsequently call the original decorator, passing runtime attribute to it.
Here is a working example (f-strings require python 3.6):
import functools
# imagine this is at some different place and cannot be changed
def check_authorization(some_attr, url):
def decorator(func):
@functools.wraps(func)
def wrapper(*args, **kwargs):
print(f"checking authorization for '{url}'...")
return func(*args, **kwargs)
return wrapper
return decorator
# another dummy function to make the example work
def do_work():
print("work is done...")
###################
# wrapped wrapper #
###################
def custom_check_authorization(some_attr):
def decorator(func):
# assuming this will be used only on this particular class
@functools.wraps(func)
def wrapper(self, *args, **kwargs):
# get url
url = self.url
# decorate function with original decorator, pass url
return check_authorization(some_attr, url)(func)(self, *args, **kwargs)
return wrapper
return decorator
#############################
# original example, updated #
#############################
class Client(object):
def __init__(self, url):
self.url = url
@custom_check_authorization("some_attr")
def get(self):
do_work()
# create object
client = Client(r"https://stackoverflow.com/questions/11731136/class-method-decorator-with-self-arguments")
# call decorated function
client.get()
output:
checking authorisation for 'https://stackoverflow.com/questions/11731136/class-method-decorator-with-self-arguments'...
work is done...
I know this issue is quite old, but the below workaround hasn't been proposed before. The problem here is that you can't access self
in a class block, but you can in a class method.
Let's create a dummy decorator to repeat a function some times.
import functools
def repeat(num_rep):
def decorator_repeat(func):
@functools.wraps(func)
def wrapper_repeat(*args, **kwargs):
for _ in range(num_rep):
value = func(*args, **kwargs)
return
return wrapper_repeat
return decorator_repeat
class A:
def __init__(self, times, name):
self.times = times
self.name = name
def get_name(self):
@repeat(num_rep=self.times)
def _get_name():
print(f'Hi {self.name}')
_get_name()
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