georgeryo...@gmail.com wrote:
> [python 2.7, linux]
> I have a python app. I cannot modify the file. But I can import it and
> mess with it. I need to perform brief tasks before and after some of the
> member functions.
> I'd like to do this in as clear and maintainable way as possible (no third
> party imports). Here's what I have now(which works):
>
> from newvbr import * #get all the stuff from the newvbr app.
>
> def perf_time(tag): # I do a little more than this, but you get the idea.
> print >>sys.stderr, datetime.datetime.now().isoformat() + tag
>
> def perf(tag):
> def decorator(fn):
> def wrapper(*args):
> perf_time('start %s' % tag)
> ret = fn(*args)
> perf_time('end %s' % tag)
> return ret
> return wrapper
> return decorator
>
>
> I use this on various members of various classes in the newvbr app:
>
> old_database_snapshot = VerticaSession.database_snapshot
> @perf('db_snap')
> def new_database_snapshot(self, name):
> old_database_snapshot(self, name)
> VerticaSession.database_snapshot = new_database_snapshot
>
> old_object_snapshot = VerticaSession.object_snapshot
> @perf('obj_snap')
> def new_object_snapshot(self, name):
> old_object_snapshot(self, name)
> VerticaSession.object_snapshot = new_object_snapshot
>
> main() #do the usual stuff of the imported app, but with annotations.
>
>
> This is still pretty laborious. How can I make something roughly like:
>
> super_tagger(VerticaSession.database_snapshot)
>
> that does all the above? I need to tag a bunch of function members like
> this. I don't insist on using decorators, it just looked like that kind
> of problem.
Remember that
@foo
def bar(...):
...
is just syntactic sugar for
def bar(...): ...
bar = foo(bar)
In your case the latter form is more convenient, so instead of
> old_object_snapshot = VerticaSession.object_snapshot
> @perf('obj_snap')
> def new_object_snapshot(self, name):
> old_object_snapshot(self, name)
> VerticaSession.object_snapshot = new_object_snapshot
use
VerticalSession.object_snapshot =
perf("obj_snap")(VerticalSession.object_snapshot)
If you like you can write a helper function along these lines
def wrap_attr(obj, attrname, name=None):
if name is None:
name = attrname
setattr(obj, attrname
perf(name)(getattr(obj, attrname)))
wrap_attr(VerticalSession, "object_snapshot")
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