On 02/17/2015 04:53 PM, Albert-Jan Roskam wrote:
Hi,
I would like to monkey patch a function 'decode' that is defined inside a class. It is
defined there because it is a logical place, next to its counterpart *method* 'encode'. I
can successfully monkey patch meth1, but when I call meth2, it does not use the patched
decorator. How can this be done? In this example, I would like to effectively "turn
off" @decode. I am hoping for a solution that works on Python 2.7 and 3.3+.
import inspect, functools
class Foo(object):
def decode(func):
@functools.wraps(func)
def wrapped(*args, **kwargs):
print "original decorator was called"
return func(*args, **kwargs).decode("utf-8")
return wrapped
def encode(self):
"""this is just here to show why decode() is defined
within Foo"""
pass
def meth1(self):
return "original method was called"
@decode
def meth2(self):
return b"python rocks"
I assume the monkey patching happens in some other file which will
import this one.
So by the time the import is finished, the meth2() method has already
been decorated by the decode function.
# ---- works -----
f = Foo()
print f.meth1()
Foo.meth1 = lambda self: "new method was called"
print f.meth1()
print "-------------------"
# ---- does not work -----
def patched_decode(func):
@functools.wraps(func)
def wrapped(*args, **kwargs):
print "patched decorator was called"
return func(*args, **kwargs)
return wrapped
f = Foo()
print 'ORIGINAL'
print inspect.getsource(Foo.decode) # shows source code of regular decode (as
expected)
result = f.meth2()
print repr(result), type(result)
#setattr(Foo, "decode", patched_decode)
Foo.decode = patched_decode
print 'PATCHED'
print inspect.getsource(f.decode) # shows source code of patched_decode (as
expected)
result = f.meth2()
print repr(result), type(result) # not patched at all! it's still unicode!
##### output:
In [1]: %run monkey_patch.py
original method was called
new method was called
-------------------
ORIGINAL
def decode(func):
@functools.wraps(func)
def wrapped(*args, **kwargs):
print "original decorator was called"
return func(*args, **kwargs).decode("utf-8")
return wrapped
original decorator was called
u'python rocks' <type 'unicode'>
PATCHED
def patched_decode(func):
@functools.wraps(func)
def wrapped(*args, **kwargs):
print "patched decorator was called"
return func(*args, **kwargs)
return wrapped
original decorator was called
u'python rocks' <type 'unicode'>
I think you're going to have to patch meth2(). Patching decode won't
help, since it's already done its work.
--
DaveA
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