function decorator-like function
vsoler
Still learning Python, now decorators.
Before diving deeply into decorators, I'd like to apply a function to
another function.
My "extremely simple function" should print number 3, then the sum of
its 2 arguments.
Say that I call f(5,7)
I'd like to get, somehow, 3 then 12.
I've tried the following:
def d(f):
print 3
return f
def f(a, b):
print a+b
f=d(f)
However, it does not work. Calling f(5,7) only returns 12, (3 is
missing)
How should I proceed?
Patrick Maupin
>>> def d(f):
... def wrapper(*args):
... print 3
... return f(*args)
... return wrapper
...
>>> def f(a, b):
... print a + b
...
>>> f = d(f)
>>> f(5, 7)
3
12
HTH,
Pat
vsoler
Pat,
I think some lines are missing. I don't see "d" function defined. Any
lines above def wrapper?
Thank you
vsoler
Patrick,
I see what happened. The first line was somehow hidden.
Thank you very much.
Vicente Soler
Patrick Maupin
> I see what happened. The first line was somehow hidden.
> Thank you very much.
You're welcome. Sorry about the formatting. Also, note that if your
decorator is complicated, you might want to use a class instead of a
nested function. Here's the same thing, using a class (and using the
actual decorator syntax):
class d(object):
def __init__(self, func):
self.func = func
def __call__(self, *args):
print 3
return self.func(*args)
@d
def f(a, b):
print a + b
f(5, 7)
Pat
Michele Simionato
pypi.python.org/pypi/decorator):
from decorator import decorator
@decorator
def d(func, *args):
print 3
return func(*args)
Patrick Maupin
wrote:
That looks cool (and I'm glad you mentioned it), but it appeared to me
the OP was trying to manually construct the equivalent of a decorator
without the "@" syntax, in order to gain an understanding of how
decorators work, and for this particular purpose, piling additional
magic on top of decorators is probably not helpful :-)
Regards,
Pat