On 5 Jun 2006, at 6:58 am, James Bennett wrote:
>
> On 6/4/06, David Robinson <[EMAIL PROTECTED]> wrote:
>> Really, I've tried looking this one up myself (you wouldn't
>> believe how
>> many questions I *haven't* had to ask... (thanks for well-written
>> docs
>> everyone)). It seems almost obvious, but I am proving to be just
>> dense
>> enough to not get what is this "kwarg".
>
> It's a shorthand for 'keyword argument'.
>
> Minor OT explanation, since it's a useful Python concept:
>
> Arguments to a function can be either positional (where the function
> figures out which argument is which based on the order they come in),
> or keyword (where they're pass as name/value pairs, like
> "Poll.objects.get(pk=1)" -- "pk=1" is a keyword argument).
>
> Python provides shortcuts for passing lots of these, and you'll see
> them used all over the place in Django. For example, you could do
>
> my_func('foo', 'bar', 'baz')
>
> and 'foo', 'bar' and 'baz' would be positional arguments. But you can
> also build up a list, and pass it directly to a function, like so:
>
> my_args = ['foo', 'bar', 'baz']
> my_func(*my_args)
>
> The asterisk tells Python "take this list and treat it as the
> positional arguments". Often when you don't know in advance what the
> arguments are giong to be, this is a lot easier. The same is true of
> keyword arguments; instead of
>
> my_func(foo=bar, baz=quux)
>
> you can build a dictionary and pass it to the function:
>
> my_kwargs = {'foo': 'bar', 'baz': 'quux'}
> my_func(**my_kwargs)
>
> The double-asterisk tells Python "take this dictionary and treat it as
> the keyword arguments".
>
> That's why there are lots of places in Django where you'll see
> things like
>
> some_func(*args, **kwargs)
>
> What's happened is that the positional arguments have been put into a
> list called 'args' as they were figured out, and the keyword arguments
> into a dictionary called 'kwargs' -- the names serve as a reminder of
> what they're for -- and then the list and the dictionary are handed
> off to the function.
Thanks for clearing that up, I'd often wondered what they were ;)
Cheers,
Dave
--
David Reynolds
[EMAIL PROTECTED]
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