On Tue, Feb 28, 2017 at 9:12 AM, David Mertz <mertz@gnosis.cx> wrote:
The difference in hits might be because MappingProxyType has a funny name and is in a hidden-ish location. I.e. not necessarily because it *would be* less used or useful if it were more exposed.
It also might be because you can use `frozenset` in python2.x code -- And there's lots of that lying around...
In either case, the name that makes sense to me would be `frozendict`. That could very well live in `collections` of course.
Yes, I agree. Though it'd also probably need to be hashable if we were to give it that name. I'm not 100% sure that `MappingProxyType` works there as it's just a view into another mapping. If the first mapping changes, so does the hash. This is the same problem we have hashing tuple in some sense -- But tuple can say "Nope, sorry. I can't hash this because it's got an unhashable member". I don't think we can really do the same thing with a MappingProxy since most of the time, it'll be constructed from something else. I suppose the workaround is pretty simple though:
class frozendict(MappingProxyType):
def __init__(self, proxy):
super().__init__(proxy.copy()) # Copy the proxy! -- Maybe need `copy.copy()` instead?
super().__init__(proxy.copy()) # Copy the proxy! -- Maybe need `copy.copy()` instead?
def __hash__(self):
return hash(frozenset(self.items()))
return hash(frozenset(self.items()))
This could likely be done better, but hopefully it gets the idea across...
--On Tue, Feb 28, 2017 at 7:40 AM, Ivan Levkivskyi <levkivskyi@gmail.com> wrote:IvanSearching MappingProxyType on GitHub gives over 10,000 results.I am not sure if it makes sense to move it to builtins. (for comparison frozenset gives around 1000,000 results)
I think it probably makes sense to make mappingproxy more "visible",
maybe move it to collections module? (where OrderedDict lives)
--On 28 February 2017 at 16:24, Joseph Hackman <josephhackman@gmail.com> wrote:+1
I think this makes a lot of sense. What would you name the built in?
-Joseph
> On Feb 28, 2017, at 7:17 AM, Michel Desmoulin <desmoulinmichel@gmail.com> wrote:
>
> We have the immutable frozenset for sets and and tuples for lists.
>
> But we also have something to manipulate dict as immutable datastructures:
>
>>>> from types import MappingProxyType as idict
>>>> d = idict({'a':1, 'b':2, 'c':3})
>>>> d['a'] = 4
> Traceback (most recent call last):
> File "<ipython-input-3-c6f93d6278af>", line 1, in <module>
> d['a'] = 4
> TypeError: 'mappingproxy' object does not support item assignment
>
> We could expose this as a built type to allow the last of the most
> important data structure in Python to be easily immutable.
>
> _______________________________________________
> Python-ideas mailing list
> Python-ideas@python.org
> https://mail.python.org/mailman/listinfo/python-ideas
> Code of Conduct: http://python.org/psf/codeofconduct/
_______________________________________________
Python-ideas mailing list
Python-ideas@python.org
https://mail.python.org/mailman/listinfo/python-ideas
Code of Conduct: http://python.org/psf/codeofconduct/
_______________________________________________
Python-ideas mailing list
Python-ideas@python.org
https://mail.python.org/mailman/listinfo/python-ideas
Code of Conduct: http://python.org/psf/codeofconduct/ Keeping medicines from the bloodstreams of the sick; food
from the bellies of the hungry; books from the hands of the
uneducated; technology from the underdeveloped; and putting
advocates of freedom in prisons. Intellectual property is
to the 21st century what the slave trade was to the 16th.
_______________________________________________
Python-ideas mailing list
Python-ideas@python.org
https://mail.python.org/mailman/listinfo/python-ideas
Code of Conduct: http://python.org/psf/codeofconduct/
Matt Gilson // SOFTWARE ENGINEER
E: matt@getpattern.com // P: 603.892.7736
We’re looking for beta testers. Go here to sign up!