Decorators not worth the effort
Thomas Rachel
nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915 at spamschutz.glglgl.de
Sat Sep 15 03:13:16 EDT 2012
[Sorry, my Firefox destroyed the indent...
Am 14.09.2012 22:29 schrieb Terry Reedy:
> In other words
>
> def make_wrapper(func, param):
> def wrapper(*args, **kwds):
> for i in range(param):
> func(*args, **kwds)
> return wrapper
>
> def f(x): print(x)
> f = make_wrapper(f, 2)
> f('simple')
>
> # is simpler, at least for some people, than the following
> # which does essentially the same thing.
>
> def make_outer(param):
> def make_inner(func):
> def wrapper(*args, **kwds):
> for i in range(param):
> func(*args, **kwds)
> return wrapper
> return make_inner
>
> @make_outer(2)
> def f(x): print(x)
> f('complex')
For this case, my mydeco.py which I use quite often contains a
def indirdeco(ind):
# Update both the outer as well as the inner wrapper.
# If we knew the inner one was to be updated with something
# from *a, **k, we could do it. But not this way...
@functools.wraps(ind)
def outer(*a, **k):
@functools.wraps(ind)
def inner(f):
return ind(f, *a, **k)
return inner
return outer
so I can do
@indirdeco
def make_wrapper(func, param):
@functools.wraps(func)
def wrapper(*args, **kwds):
for i in range(param):
func(*args, **kwds)
return wrapper
and then nevertheless
@make_wrapper(2)
def f(x): print(x)
BTW, I also have a "meta-decorator" for the other direction:
def wrapfunction(mighty):
"""Wrap a function taking (f, *a, **k) and replace it with a
function taking (f) and returning a function taking (*a, **k) which
calls our decorated function.
Other direction than indirdeco."""
@functools.wraps(mighty)
def wrapped_outer(inner):
@functools.wraps(inner)
def wrapped_inner(*a, **k):
return mighty(inner, *a, **k)
wrapped_inner.func = inner # keep the wrapped function
wrapped_inner.wrapper = mighty # and the replacement
return wrapped_inner
wrapped_outer.func = mighty # keep this as well
return wrapped_outer
With this, a
@wrapfunction
def twice(func, *a, **k):
return func(*a, **k), func(*a, **k)
can be used with
@twice
def f(x): print (x); return x
very nicely.
Thomas
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