Sorry for top posting, but yes excepting you don't need the parens after
log in the @log line.
Sent from my Fonepad
Alex Hall <ah...@autodist.com> wrote:
Okay, I think I follow. So a decorator to log that a function ran might
be:
import utils
@log()
def run():
** #do things
#utils.py
logger = #set up logging
def log(f):
** def logThatFRan(*args, **kwargs):
****** [1]logger.info("running %s" %(f.__name__)
****** return f(*args, **kwargs)
** return logThatFRan
That will log that F ran, then run f with any arguments. I know I'd have
to decorate the inner function with functools.wraps for __name__ to work
correctly, but that's the general idea, right?
On Tue, Jul 5, 2016 at 10:40 AM, Alan Gauld via Tutor
<[2]tutor@python.org> wrote:
On 05/07/16 14:22, Alex Hall wrote:
> To simplify things, what might be an example of a decorator that, say,
> prints "decorated" before whatever string the decorated function
prints?
> My attempt would be:
>
> def prependDecorated(f):
>** **def prepend():
>** ** **return "decorated"+f()
>** **#something should go at this level too?
Recall that a decorator is:
a function
that takes a function as its argument
and returns a function
Your code fails on the third item.
Lets take a trivial example first, a decorator that
does nothing. Define a function that takes a function
and returns the same function untouched:
>>> def donothing(f): return f
Now apply it to a square() function:
>>> @donothing
def square(x): return x*x
>>> square
<function square at 0x7f3633fcb0d0>
>>> square(4)
16
We could do the same without the @ shorthand by using
square2 = donothing(square)
But the @ syntax makes it more readable.
Now lets look at your task
We need a function that takes a function and
returns a function that prepends a string:
def prepend(f):
** ** def add_string(*args, **kwargs):** # in case f takes arguments
** ** ** ** return "decorated "+ str(f(*args,**kwargs))
** ** return add_string
Now we can apply that to a function
@prepend
def cube(n): return n*n*n
cube(3)
I'm biased because I was the tech editor but the book
Professional Python has a nice chapter on decorators.
HTH
--
Alan G
Author of the Learn to Program web site
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