Newbie: How can I use a string value for a keyword argument?

[John Machin]

On Feb 25, 10:42 pm, Doug Morse <mo... at edoug.org> wrote:
> Hi,
>
> My apologies for troubling for what is probably an easy question... it's just
> that can't seem to find an answer to this anywhere (Googling, pydocs, etc.)...
>
> I have a class method, MyClass.foo(), that takes keyword arguments.  For
> example, I can say:
>
> x = MyClass()
> x.foo(trials=32)
>
> Works just fine.
>
> What I need to be able to do is call foo() with a string value specifying the
> keyword (or both the keyword and value would be fine), something along the
> lines of:
>
> x = MyClass()
> y = 'trials=32'
> x.foo(y)        # doesn't work
>
> or
>
> x.MyClass()
> y = 'trials'
> x.foo(y = 32)   # does the "wrong" thing
>
> Surely there's some way to use a string's value as the key for making a method
> call with a keyword argument?
>
> Just for completeness, my goal is simply to read a bunch of key/value pairs
> from an INI file (using ConfigObj) and then use those key/value pairs to set a
> (3rd party) object's parameters, which must be done with a call along the
> lines of "instance.set(key=value)".  Obviously, I could create a huge if..elif
> statement along the lines of "if y = 'trials': x.foo(trials=32); elif y =
> 'speed': x.foo(speed=12);" etc., but then the statement has to be maintained
> every time a new parameter is added/changed etc.  Plus, such a solution seems
> to me grossly inelegant and un-Pythonic.
>

I'm not quite sure what foo() is really supposed to do ... however the
built-in function setattr is your friend. Assuming that ini_dict
contains what you have scraped out of your .ini file, you can do:
    x = MyCLass()
    for key, value in ini_dict.items():
        setattr(x, key, value)
You may prefer (I would) to do it inside the class, and maybe do some
checking/validation:
    class MyClass(object):
        def load(self, adict):
            for k, v in adict.items():
                # do checking here
                setattr(self, k, v)
   # much later
   x = MyClass()
   x.load(ini_dict)

HTH,
John