<div dir="ltr"><div class="gmail_extra">I've implemented `frozendict` a few times for various projects and never knew about MappingProxyType. I always used `collections.abc.Mapping` ...</div><div class="gmail_extra"><br></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Feb 28, 2017 at 9:12 AM, David Mertz <span dir="ltr"><<a href="mailto:mertz@gnosis.cx" target="_blank">mertz@gnosis.cx</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">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.<div><br></div></div></blockquote><div><br></div><div>It also might be because you can use `frozenset` in python2.x code -- And there's lots of that lying around...</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div></div><div>In either case, the name that makes sense to me would be `frozendict`. That could very well live in `collections` of course.<br></div></div></blockquote><div><br></div><div>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:</div><div><br></div><div>class frozendict(MappingProxyType):</div><div> def __init__(self, proxy):<br> super().__init__(proxy.copy()) # Copy the proxy! -- Maybe need `copy.copy()` instead?<br></div><div> def __hash__(self):<br> return hash(frozenset(self.items()))</div><div><br></div><div>This could likely be done better, but hopefully it gets the idea across...</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div><div class="gmail_extra"><div><div class="h5"><br><div class="gmail_quote">On Tue, Feb 28, 2017 at 7:40 AM, Ivan Levkivskyi <span dir="ltr"><<a href="mailto:levkivskyi@gmail.com" target="_blank">levkivskyi@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div><div>Searching MappingProxyType on GitHub gives over 10,000 results.<br>I think it probably makes sense to make mappingproxy more "visible",<br>maybe move it to collections module? (where OrderedDict lives)<br><br></div>I am not sure if it makes sense to move it to builtins. (for comparison frozenset gives around 1000,000 results)<br><br>--<br></div>Ivan <br><div><div><br><br></div></div></div><div class="m_-9196022794170621541HOEnZb"><div class="m_-9196022794170621541h5"><div class="gmail_extra"><br><div class="gmail_quote">On 28 February 2017 at 16:24, Joseph Hackman <span dir="ltr"><<a href="mailto:josephhackman@gmail.com" target="_blank">josephhackman@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">+1<br>
<br>
I think this makes a lot of sense. What would you name the built in?<br>
<span class="m_-9196022794170621541m_-6159540040656993137HOEnZb"><font color="#888888"><br>
-Joseph<br>
</font></span><div class="m_-9196022794170621541m_-6159540040656993137HOEnZb"><div class="m_-9196022794170621541m_-6159540040656993137h5"><br>
> On Feb 28, 2017, at 7:17 AM, Michel Desmoulin <<a href="mailto:desmoulinmichel@gmail.com" target="_blank">desmoulinmichel@gmail.com</a>> wrote:<br>
><br>
> We have the immutable frozenset for sets and and tuples for lists.<br>
><br>
> But we also have something to manipulate dict as immutable datastructures:<br>
><br>
>>>> from types import MappingProxyType as idict<br>
>>>> d = idict({'a':1, 'b':2, 'c':3})<br>
>>>> d['a'] = 4<br>
> Traceback (most recent call last):<br>
> File "<ipython-input-3-c6f93d6278af<wbr>>", line 1, in <module><br>
> d['a'] = 4<br>
> TypeError: 'mappingproxy' object does not support item assignment<br>
><br>
> We could expose this as a built type to allow the last of the most<br>
> important data structure in Python to be easily immutable.<br>
><br>
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