On Mon, 15 Mar 2010 05:38:43 -0700 (PDT)
Karjer Jdfjdf <[email protected]> wrote:
> I want to use **kwargs to check a list of conditions (if true do this, if
> false do nothing) besides required parameters ( in sample a and b).
> Sometimes I want to add a Python object (in example a dictionary and a list).
> Below is my first **kwargs-brew.
>
> ###START
>
> def function_with_kwargs(a, b, **kwargs):
> options = {
> 'logfile' : None,
> 'door' : 'kitchendoor',
> 'roof' : 'tiles',
> 'mydict' : None,
> 'mylist' : None, }
> options.update(kwargs)
The default set of options is a constant independant of the function and of its
(other) arguments. So, I would rather define it outside. I find it clearer.
from copy import copy
OPTIONS = {
'logfile' : None,
'door' : 'kitchendoor',
'roof' : 'tiles',
'mydict' : None,
'mylist' : None,
}
def function_with_kwargs(a, b, **kwargs):
options = copy(OPTIONS)
options.update(kwargs)
print options
(Must be copied to avoid the defaults to be altered by update.)
> logfile = options.get('logfile')
> if logfile == None:
> print "No logging"
> else:
> print "Logging"
You don't need to use get, use options['logfile'] instead. Get is only useful
if you use its default_value parameter. This would indeed be a good alternative
to a global default dict for options:
logfile = options.get('logfile', None)
...
roof = options.get('roof', 'tiles')
or maybe better the general pattern:
x = options.get('x', OPTIONS['x'])
> mydict = options.get('mydict')
> if mydict == None:
> print "Do nothing with dictionary"
> else:
> print "Do something with dictionary"
>
> mylist = options.get('mylist')
> if mylist == None:
> print "Do nothing with list"
> else:
> print "Do something with list"
>
> print "END OF FUNCTION\n"
>
>
> somedict = { 'a': '1', 'b': '2', }
> somelist = ['1', '2']
>
> #DO SOMETHING
> function_with_kwargs(1, 2, logfile='log.txt', door='frontdoor',
> mydict=somedict, mylist=somelist)
>
> #DO NOTHING
> function_with_kwargs(1, 2, door='frontdoor')
>
>
>
> ### END
>
> I have 2 questions about this code:
>
> 1. Can I use this in Python 3 ? I'm not sure if I can use **kwargs in Python
> 3 because it uses the "apply" builtin (if I understand it correctly)
>
> "At this writing, both apply and the special call syntax described in this
> section can be used freely in Python 2.5, but it seems likely that apply
> may go away in Python 3.0. If you wish to future-proof your code, use
> the equivalent special call syntax, not apply."
>
> 2. Are there better ways to achieve what I want to do?
In this case, I would use a general config object, which attributes are
individual parameters. You need to first define a fake Config class (because
for any reason we cannot alter direct instances of object).
Denis
________________________________
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