[Python-ideas] Docstrings for namedtuple

[Terry Reedy]

On 12/16/2012 8:22 AM, Eli Bendersky wrote:

> This may be a good time to say that personally I always disliked
> namedtuple's creation syntax. It is unpleasant in two respects:
>
> 1. You have to repeat the name
> 2. You have to specify the fields in a space-separated string
>
> I wish there was an alternative of something like:
>
> @namedtuple
> class Point:
>    x = 0
>    y = 0

Pretty easy, once one figures out metaclass basics.

import collections as co

class ntmeta():
     def __prepare__(name, bases, **kwds):
         return co.OrderedDict()
     def __new__(cls, name, bases, namespace):
         print(namespace) # shows why filter is needed
         return co.namedtuple(name,
                 filter(lambda s: s[0] != '_', namespace))

class Point(metaclass=ntmeta):
     x = 0
     y = 0

p = Point(1,2)
print(p)
#
OrderedDict([('__module__', '__main__'), ('__qualname__', 'Point'), 
('x', 0), ('y', 0)])
Point(x=1, y=2)

To use the filtered namespace values as defaults (Antoine's suggestion), 
first replace namedtuple() with its body.
Then modify the header of generated name.__new__. For Point, change

def __new__(_cls, x, y):
#to
def __new__(_cls, x=0, y=0):

Also change the newclass docstring. For Point, change
     'Point(x, y)'
to
     'Point(x=0, y=0)'

-- 
Terry Jan Reedy