09.04.18 00:18, Andrés Delfino пише:
I thought that maybe dict could accept several mappings as positional arguments, like this:

    class Dict4(dict):
         def __init__(self, *args, **kwargs):
             if len(args) > 1:
                 if not all([isinstance(arg, dict) for arg in args]):
                     raise TypeError('Dict4 expected instances of dict
    since multiple positional arguments were passed')

                 temp = args[0].copy()

                 for arg in args[1:]:
                     temp.update(arg)

                 super().__init__(temp, **kwargs)
             else:
                 super().__init__(*args, **kwargs)


AFAIK, this wouldn't create compatibility problems, since you can't pass two positional arguments now anyways.

It would be useful to solve the "sum/union dicts" discussion, for example: requests.get(url, params=dict(params, {'foo': bar})

Whar are your thoughts?

It is easy to make the dict constructor merging several positional arguments. But this is not a tiny harmless change, it will start a cascade of other changes.

After changing the dict constructor, we will need to update the dict.update() method too. Constructors and update() methods of dict subclasses (OrderedDict, defaultdict, Counter, and more specialized classes) should be updated too. UserDict, WeakKeyDictionary, WeakValueDictionary are next. After that we will have a pressure of updating constructors and update() methods of abstract classes Mapping and MutableMapping. This change will break a lot of third-party code that implement concrete implementations of these classes, because adding support of new arguments in the method of abstract class breaks an interface.

We will be able to pass this path (we have already passed it), but we must realize how long it is.

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