Is there a simpler way to modify all arguments in a function before using the arguments?

brucegoodstein at gmail.com brucegoodstein at gmail.com
Fri Nov 16 00:20:10 CET 2012


On Saturday, November 10, 2012 10:35:12 AM UTC-5, Aahz wrote:
> In article <mailman.3530.1352538537.27098.python-list at python.org>,
> 
> Peter Otten  <__peter__ at web.de> wrote:
> 
> >Miki Tebeka wrote:
> 
> >
> 
> >>> Is there a simpler way to modify all arguments in a function before using
> 
> >>> the arguments?
> 
> >>
> 
> >> You can use a decorator:
> 
> >> 
> 
> >> from functools import wraps
> 
> >> 
> 
> >> def fix_args(fn):
> 
> >>     @wraps(fn)
> 
> >>     def wrapper(*args):
> 
> >>         args = (arg.replace('_', '') for arg in args)
> 
> >>         return fn(*args)
> 
> >> 
> 
> >>     return wrapper
> 
> >> 
> 
> >> @fix_args
> 
> >> def foo(x, y):
> 
> >>     print(x)
> 
> >>     print(y)
> 
> >
> 
> >I was tempted to post that myself, but he said /simpler/ ;)
> 
> 
> 
> From my POV, that *is* simpler.  When you change the parameters for foo,
> 
> you don't need to change the arg pre-processing.  Also allows code reuse,
> 
> probably any program needing this kind of processing once will need it
> 
> again.
> 
> -- 
> 
> Aahz (aahz at pythoncraft.com)           <*>         http://www.pythoncraft.com/
> 
> 
> 
> "....Normal is what cuts off your sixth finger and your tail..."  --Siobhan

Using a decorator works when named arguments are not used. When named arguments are used, unexpected keyword error is reported. Is there a simple fix?

Thanks to all,
Bruce

Code:
-----

from functools import wraps

def fix_args(fn):
    @wraps(fn)
    def wrapper(*args):
        args = (arg.replace('_', '') for arg in args)
        return fn(*args)
    return wrapper
    
@fix_args
def foo(a1="", a2="", b1="", b2=""):
     print(a1)
     print(a2) 
     print(b1)
     print(b2) 
     
foo ('a1a1_x', 'a2a2_x', 'b1b1_x', 'b2b2_____x')
foo (a1='a1a1_x', a2='a2a2_x', b1='b1b1_x', b2='b2b2_____x')

Results:
--------
a1a1x
a2a2x
b1b1x
b2b2x
Traceback (most recent call last):
  File "C:\WORK\masterDB_Update\argtest.py", line 19, in <module>
    foo (a1='a1a1_x', a2='a2a2_x', b1='b1b1_x', b2='b2b2_____x')
TypeError: wrapper() got an unexpected keyword argument 'a1'


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