[Python-ideas] Short form for keyword arguments and dicts

[Eric V. Smith]

On 6/24/2013 2:03 PM, Terry Reedy wrote:
> On 6/24/2013 12:23 PM, Andrew McNabb wrote:
> 
>> Another use case where this would come in handy is with string
>> formatting:
>>
>>>>> print('{spam} and {eggs}'.format(spam=spam, eggs=eggs))
>>
>> I've seen people use an awful workaround for this:
>>
>>>>> print('{spam} and {eggs}'.format(locals()))
> 
> That should be
> print('{spam} and {eggs}'.format(**locals()))

or:
print('{spam} and {eggs}'.format_map(locals()))

which solves the inefficiency problem mentioned below.

> Why do you see an intended usage as an 'awful workaround'?
> 
> If it is the inefficiency of unpacking and repacking a dict, that could
> be fixed. One possibility is for ** to just pass the mapping when the
> function only reads it, as is the case with .format (but how to know?).
> A direct solution for .format is to add a keyword-only mapping
> parameter:
> 
> print('{spam} and {eggs}'.format(map=locals()))

Today that would be:
print('{map.spam} and {map.eggs}'.format(map=locals()))

-- 
Eric.