[EMAIL PROTECTED] schrieb:
I am instantiating a class A (which I am importing from somebody
else, so I can't modify it) into my class X.
Is there a way I can intercept or wrape calls to methods in A?
I.e., in the code below can I call
x.a.p1()
and get the output
X.pre
A.p1
X.post
Many TIA!
Mark
class A:
# in my real application, this is an imported class
# that I cannot modify
def p1(self): print 'A.p1'
class X:
def __init__(self):
self.a=A()
def pre(self): print 'X.pre'
def post(self): print 'X.post'
x=X()
x.a.p1()
There are a few ways to accompish this. First of all, Python allows
monkey-patching. That means you *can* modify it:
import sys
class X(object):
def foo(self):
print "foo"
X.foo = lambda self: sys.stdout.write("more than foo")
x = X()
x.foo()
You can of course wrap the old foo instead of replacing it, with
something like
def foowrapper(old_foo):
def _w(self, *args, **kwargs):
print "wrapped"
return old_foo(self, *args, **kwargs)
return _w
X.foo = foowrapper(X.foo)
Alternatively, you can wrap the whole of X into a proxy, based on
__getattr__ that will allow you do intercept all delegate calls.
class Wrapper(object):
def __init__(self, delegate):
self._delegate = delegate
def __getattr__(self, name):
print "accessing", name
return getattr(self._delegate, name)
Diez
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