decorator question

[Schüle Daniel]

hello NG,

consider this code
[color=blue][color=green][color=darkred]
>>> def timelogger(f):[/color][/color][/color]
.... def wrapper(*a,**kw ):
.... print "started at %s" % time.ctime()
.... t0 = time.time()
.... f(*a, **kw)
.... t1 = time.time()
.... print "ended at %s" % time.ctime()
.... print "diff = ", t1-t0, "sec"
.... return wrapper
....[color=blue][color=green][color=darkred]
>>> import time
>>> @timelogger[/color][/color][/color]
.... def loops(a,b,c):
.... sum = 0
.... for i in range(a):
.... for j in range(b):
.... for k in range(c):
.... sum += 1
....[color=blue][color=green][color=darkred]
>>> loops[/color][/color][/color]
<function wrapper at 0x402eec34>[color=blue][color=green][color=darkred]
>>> loops(10,10,10)[/color][/color][/color]
started at Sun Jan 8 23:19:19 2006
ended at Sun Jan 8 23:19:19 2006
diff = 0.0003671646118 16 sec

the code above works fine
but I am wondering wheather it's possible to
write something like this
[color=blue][color=green][color=darkred]
>>> def timelogger(f, logfile=sys.std out):[/color][/color][/color]
.... def wrapper(*a,**kw ):
.... logfile.write(" started at %s" % time.ctime())
.... t0 = time.time()
.... f(*a, **kw)
.... t1 = time.time()
.... logfile.write(" ended at %s" % time.ctime())
.... logfile.write(" diff = %f %s" % (t1-t0, "sec"))
.... return wrapper
[color=blue][color=green][color=darkred]
>>> import time
>>> @timelogger(fil e("hierher", "a")) ### <<<<<< (1)[/color][/color][/color]
.... def loops(a,b,c):
.... sum = 0
.... for i in range(a):
.... for j in range(b):
.... for k in range(c):
.... sum += 1
....

(1) fails to compile
is it possible to pass parameters to a decorator function?

Regards, Daniel

[Frank Niessink]

Re: decorator question

Schüle Daniel wrote:[color=blue]
>
> (1) fails to compile
> is it possible to pass parameters to a decorator function?[/color]

Yes, I think this does what you want:

import time, sys

def timelogger(logf ile=sys.stdout) :
def actual_timelogg er(function):
def wrapper(*a,**kw ):
logfile.write(" started at %s" % time.ctime())
t0 = time.time()
function(*a, **kw)
t1 = time.time()
logfile.write(" ended at %s" % time.ctime())
logfile.write(" diff = %f %s" % (t1-t0, "sec"))
return wrapper
return actual_timelogg er

@timelogger(log file=file("hier her", "a")) ### <<<<<< (1)
def loops(a,b,c):
sum = 0
for i in range(a):
for j in range(b):
for k in range(c):
sum += 1


loops(100,100,1 00)


Cheers, Frank

[Ralf Schmitt]

Re: decorator question

Schüle Daniel schrieb:[color=blue]
> hello NG,
>
> consider this code
>[color=green][color=darkred]
> >>> def timelogger(f):[/color][/color]
> ... def wrapper(*a,**kw ):
> ... print "started at %s" % time.ctime()
> ... t0 = time.time()
> ... f(*a, **kw)
> ... t1 = time.time()
> ... print "ended at %s" % time.ctime()
> ... print "diff = ", t1-t0, "sec"
> ... return wrapper
> ...[color=green][color=darkred]
> >>> import time
> >>> @timelogger[/color][/color]
> ... def loops(a,b,c):
> ... sum = 0
> ... for i in range(a):
> ... for j in range(b):
> ... for k in range(c):
> ... sum += 1
> ...[color=green][color=darkred]
> >>> loops[/color][/color]
> <function wrapper at 0x402eec34>[color=green][color=darkred]
> >>> loops(10,10,10)[/color][/color]
> started at Sun Jan 8 23:19:19 2006
> ended at Sun Jan 8 23:19:19 2006
> diff = 0.0003671646118 16 sec
>
> the code above works fine
> but I am wondering wheather it's possible to
> write something like this
>[color=green][color=darkred]
> >>> def timelogger(f, logfile=sys.std out):[/color][/color]
> ... def wrapper(*a,**kw ):
> ... logfile.write(" started at %s" % time.ctime())
> ... t0 = time.time()
> ... f(*a, **kw)
> ... t1 = time.time()
> ... logfile.write(" ended at %s" % time.ctime())
> ... logfile.write(" diff = %f %s" % (t1-t0, "sec"))
> ... return wrapper
>[color=green][color=darkred]
> >>> import time
> >>> @timelogger(fil e("hierher", "a")) ### <<<<<< (1)[/color][/color]
> ... def loops(a,b,c):
> ... sum = 0
> ... for i in range(a):
> ... for j in range(b):
> ... for k in range(c):
> ... sum += 1
> ...
>
> (1) fails to compile
> is it possible to pass parameters to a decorator function?
>[/color]

It's possible. The call to timelogger must return a function which
itself takes a function and returns one:

def timelogger(logf ile=sys.stdout) :
def deco(f):
def wrapper(*a,**kw ):
logfile.write(" started at %s" % time.ctime())
t0 = time.time()
f(*a, **kw)
t1 = time.time()
logfile.write(" ended at %s" % time.ctime())
logfile.write(" diff = %f %s" % (t1-t0, "sec"))
return wrapper
return deco

[color=blue]
> Regards, Daniel
>[/color]

[Bengt Richter]

Re: decorator question

On Sun, 08 Jan 2006 23:26:28 +0100, =?ISO-8859-1?Q?Sch=FCle_Da niel?= <uval@rz.uni-karlsruhe.de> wrote:
[...][color=blue]
>
>the code above works fine
>but I am wondering wheather it's possible to
>write something like this
>[color=green][color=darkred]
> >>> def timelogger(f, logfile=sys.std out):[/color][/color]
>... def wrapper(*a,**kw ):
>... logfile.write(" started at %s" % time.ctime())
>... t0 = time.time()
>... f(*a, **kw)
>... t1 = time.time()
>... logfile.write(" ended at %s" % time.ctime())
>... logfile.write(" diff = %f %s" % (t1-t0, "sec"))
>... return wrapper
>[color=green][color=darkred]
> >>> import time
> >>> @timelogger(fil e("hierher", "a")) ### <<<<<< (1)[/color][/color]
>... def loops(a,b,c):
>... sum = 0
>... for i in range(a):
>... for j in range(b):
>... for k in range(c):
>... sum += 1
>...
>
>(1) fails to compile
>is it possible to pass parameters to a decorator function?
>[/color]
Yes, but then the function must return the same kind of thing
a bare decorator-function name would have, which is a function
able to take a single argument of a function and return a function.

So your decorator won't take f as an argument, just the optional logfile,
and it will return a function that does the wrapping like the original decorator.
[color=blue][color=green][color=darkred]
>>> import sys, time
>>> def timelogger(logf ile=sys.stdout) :[/color][/color][/color]
... def deco(f):
... def wrapper(*a,**kw ):
... logfile.write(" started at %s\n" % time.ctime())
... t0 = time.time()
... f(*a, **kw)
... t1 = time.time()
... logfile.write(" ended at %s\n" % time.ctime())
... logfile.write(" diff = %f %s\n" % (t1-t0, "sec"))
... return wrapper
... return deco
...[color=blue][color=green][color=darkred]
>>> @timelogger() # stdout[/color][/color][/color]
... def foo(): pass
...[color=blue][color=green][color=darkred]
>>> foo()[/color][/color][/color]
started at Sun Jan 08 14:13:55 2006
ended at Sun Jan 08 14:13:55 2006
diff = 0.000000 sec[color=blue][color=green][color=darkred]
>>> foo()[/color][/color][/color]
started at Sun Jan 08 14:14:02 2006
ended at Sun Jan 08 14:14:02 2006
diff = 0.000000 sec[color=blue][color=green][color=darkred]
>>> @timelogger() # stdout[/color][/color][/color]
... def foo(dt): time.sleep(dt)
...[color=blue][color=green][color=darkred]
>>> foo(5)[/color][/color][/color]
started at Sun Jan 08 14:14:59 2006
ended at Sun Jan 08 14:15:04 2006
diff = 5.007000 sec[color=blue][color=green][color=darkred]
>>> foo(.5)[/color][/color][/color]
started at Sun Jan 08 14:15:16 2006
ended at Sun Jan 08 14:15:17 2006
diff = 0.501000 sec[color=blue][color=green][color=darkred]
>>>[/color][/color][/color]

Regards,
Bengt Richter

[Schüle Daniel]

Re: decorator question

thx to all

now I understand how it works and why it should be done in this way
so it's possible to write more than only one declarator
[color=blue][color=green][color=darkred]
>>> def foo(f):[/color][/color][/color]
.... l = [1]
.... def method(*a,**kw) :
.... f(l, *a, **kw)
.... return method
....[color=blue][color=green][color=darkred]
>>> def bar(f):[/color][/color][/color]
.... l = [2]
.... def method(*a,**kw) :
.... f(l, *a, **kw)
.... return method
....[color=blue][color=green][color=darkred]
>>> @foo[/color][/color][/color]
.... @bar
.... def foobar(x,y,z):
.... print x
.... print y
.... print z
....[color=blue][color=green][color=darkred]
>>> foobar(1)[/color][/color][/color]
[2]
[1]
1

x and y are already binded
by the way .. to l's lists are considered to be in closure?
Or what is the right denotation for them?
Can someone give me some pointers to the metaprogramming in Python?
links etc

Regards, Daniel

[Duncan Booth]

Re: decorator question

Bengt Richter wrote:
[color=blue][color=green]
>>is it possible to pass parameters to a decorator function?
>>[/color]
> Yes, but then the function must return the same kind of thing
> a bare decorator-function name would have, which is a function
> able to take a single argument of a function and return a function.
>
> So your decorator won't take f as an argument, just the optional
> logfile, and it will return a function that does the wrapping like the
> original decorator.[/color]

This sounds to me like something that should be done using a decorator.
e.g. (everything from 'def timelogger' onwards is unchanged from the OP's
code):

def decoratorwithar gs(f):
def wrapper(*args,* *kw):
def inner(target):
return f(target, *args, **kw)
return inner
return wrapper

@decoratorwitha rgs
def timelogger(f, logfile=sys.std out):
def wrapper(*a,**kw ):
logfile.write(" started at %s" % time.ctime())
t0 = time.time()
f(*a, **kw)
t1 = time.time()
logfile.write(" ended at %s" % time.ctime())
logfile.write(" diff = %f %s" % (t1-t0, "sec"))
return wrapper

@timelogger(fil e("hierher", "a")) ### <<<<<< (1)
def loops(a,b,c):
sum = 0
for i in range(a):
for j in range(b):
for k in range(c):
sum += 1

(I think the logfile output could do with some newlines.)

[Michele Simionato]

Re: decorator question

Schüle Daniel wrote:[color=blue]
> Can someone give me some pointers to the metaprogramming in Python?
> links etc[/color]

Check the Python Wiki. For the decorators in particular I wrote a
module that
you may find useful. See

http://www.phyast.pitt.edu/~micheles/python/decorator.zip

http://www.phyast.pitt.edu/~micheles/python/documentation.html