* Stephen Hansen, on 02.07.2010 19:41:
Okay, so!
I actually never quite got around to learning to do deep and useful
magic with decorators. I've only ever done the most basic things with
them. Its all been a little fuzzy in my head: things like what order
decorators end up being called in if there's more then one, etc.
But in my current situation, what I'm wanting to do is have a decorator
that wraps a function but which takes an *optional* argument, and sets
that argument as an attribute on said function if its there.
Here's what some tweaking and playing around has gotten me, as a recipe:
import functools
def my_decorator(arg):
if callable(arg): # Stuck on 2.5. Leavemealone. :)
protocol = None
else:
protocol = arg
def wrap(fn):
print "Wrapping."
fn.protocol = protocol
@functools.wraps(fn)
def wrapper(*args, **kwargs):
print "Calling."
result = fn(*args, **kwargs)
print "Called."
return result
return wrapper
if not protocol: # argument-less decorator
print "Calling wrap."
return wrap(arg)
else:
print "Returning wrap."
return wrap
To be used as:
class Thing(object):
@expose
def test1(self, arg1):
return arg1
@expose("testing")
def test2(self, arg2):
return arg2
So, my question: am I doing this right? :) Some play-through testing
appears to work. But, the dizzying array of nested def's up there leaves
me a bit dazed, so I'm wondering if there's a simpler way to accomplish
what I'm trying to do.
If you're willing to have slightly more explicit usage code, consider e.g.
<code>
#Py3
import functools
class expose:
def __init__( self, protocol = None ):
self._protocol = protocol
def __call__( self, f ):
print( "Wrapping." )
f.protocol = self._protocol
@functools.wraps( f )
def wrapper( *args, **kwargs ):
print( "Calling." )
result = f( *args, **kwargs )
print( "Called." )
return result
return wrapper
class Thing(object):
@expose()
def test1(self, arg1):
return arg1
@expose( "testing" )
def test2(self, arg2):
return arg2
o = Thing()
print( o.test1( 1.11 ) )
print( o.test2( 2.22 ) )
</code>
Cheers & hth.,
- Alf
--
blog at <url: http://alfps.wordpress.com>
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