# vim:sw=4:et
import sys
class Aspect(object):
"""Aspect defines the aspect interface that should be implemented by
aspects.
"""
def __init__(self, method):
"""This method takes the optional arguments given to the
weave_method() function.
"""
pass
def before(self):
"""Code executed before the weaved method is executed.
"""
pass
def after(self, retval, exc):
"""Code executed after the weaved method has been executed.
"""
pass
def weave_method(method, advice_class, *advice_args, **advice_kwargs):
advice = advice_class(method, *advice_args, **advice_kwargs)
advice_before = advice.before
advice_after = advice.after
def invoke_advice(*args, **kwargs):
advice_before()
try:
retval = method(*args, **kwargs)
except Exception, e:
advice_after(None, e)
raise
else:
advice_after(retval, None)
return retval
# Replace the method with our weaved one.
try:
class_ = method.im_class
except:
# The method is actually a simple function, wrap it in its namespace;
method.func_globals[method.func_name] = invoke_advice
else:
#name = method.__name__
setattr(class_, method.__name__, invoke_advice)
return invoke_advice
class LoggerAspect(Aspect):
def __init__(self, method):
self.method = method
def before(self):
print 'entering', self.method
def after(self, retval, exc):
print 'leaving', self.method,
if exc:
print 'with exception %s(%s)' % (exc.__class__, exc)
else:
print 'with return value', retval
class ReferenceAspect(Aspect):
"""This reference keeps track of objects created by a method.
A weak reference to those objects is created and appended to reflist.
"""
def __init__(self, method, reflist):
self.method = method
self.reflist = reflist
def after(self, retval, exc):
import weakref
if retval:
self.reflist.append(weakref.ref(retval))
if __name__ == '__main__':
def test_func(arg1, arg2):
print 'test_func(): arg1:', arg1, ', arg2:', arg2
weave_method(test_func, LoggerAspect)
print 'testing test_func()'
test_func('a', 'b')
class TestClass(object):
def test_meth(self, arg1, arg2):
print 'TestClass.test_meth(): arg1:', arg1, ', arg2:', arg2
def test_exc(self):
raise ValueError, 'HELP'
#print dir(TestClass.test_meth)
#print TestClass.test_meth.im_class
#print TestClass.test_meth.im_func
#print TestClass.test_meth.im_self
weave_method(TestClass.test_meth, LoggerAspect)
weave_method(TestClass.test_exc, LoggerAspect)
tc = TestClass()
tc.test_meth(1, 2)
try:
tc.test_exc()
except ValueError, e:
print 'Caught expected exception', e
import traceback
traceback.print_exc()
else:
raise 'HUH'
