On Wed, Jun 20, 2012 at 1:51 PM, Yury Selivanov <yselivanov...@gmail.com> wrote:
> What if instead of 'optional', we have 'base_signature'
> (or 'from_signature')?
>
> sig = signature(func)
> params = OrderedDict(tuple(sig.parameters.items())[1:])
> new_sig = Signature(params, base_signature=sig)
>
> And for Paramater:
>
> param = sig.parameters['foo']
>
> param1 = Parameter('bar', base_parameter=param)
> param2 = Parameter('spam', annotation=int, base_parameter=param)
> param3 = Parameter(base_parameter=param)
> param4 = Parameter(default=42, base_parameter=param)
>
> So 'base_parameter' will be a template from which Parameter's constructor
> will copy the missing arguments.
Good thought (and better than my initial idea), but I'd follow the
model of namedtuple._replace and make it a separate instance method:
sig = signature(f)
new_sig = sig.replace(parameters=sig.parameters.values()[1:])
param = sig.parameters['foo']
param1 = param.replace(name='bar')
param2 = param.replace(name='spam', annotation=int)
param3 = param.replace() # namedtuple._replace also allows this edge case
param4 = param.replace(default=42)
Such a copy-and-override method should be the last piece needed to
make immutable Signature objects a viable approach.
Cheers,
Nick.
--
Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia
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