2018-02-27 14:59 GMT+03:00 Ned Batchelder <n...@nedbatchelder.com>: > On 2/27/18 3:52 AM, Kirill Balunov wrote: > >> a. Is this restriction for locals desirable in the implementation of >> CPython in Python 3? >> b. Or is it the result of temporary fixes for Python 2? >> > > My understanding is that the behavior of locals() is determined mostly by > what is convenient for the implementors, so that they can keep regular code > running as quickly as possible. The answer to the question, "why can't we > make locals() work more like I expect?" is, "because that would make things > slower." >
Ok, but I in this case what is the benefit in Python 3.3+ in returning a copy of dict instead of MappingProxy? Personally, I find the convenient functionality to update the local symbol >> table inside a function, similar to `globals`. >> > > Can you show us an example of why you would want to update locals through > locals()? There might be more natural ways to solve your problem. > > The example from "Is there are good DRY fix for this painful design pattern?" https://mail.python.org/pipermail/python-list/2018- February/731218.html class Foo: def __init__(self, bashful, doc, dopey, grumpy, happy, sleepy, sneezy): self.bashful = bashful # etc def spam(self, bashful=None, doc=None, dopey=None, grumpy=None, happy=None, sleepy=None, sneezy=None): if bashful is None: bashful = self.bashful if doc is None: doc = self.doc if dopey is None: dopey = self.dopey if grumpy is None: grumpy = self.grumpy if happy is None: happy = self.happy if sleepy is None: sleepy = self.sleepy if sneezy is None: sneezy = self.sneezy # now do the real work... def eggs(self, bashful=None, # etc... ): if bashful is None: bashful = self.bashful # and so on and with the possibility to update `locals` the `spam` can be rewritten with: def spam(self, bashful=None, doc=None, dopey=None, grumpy=None, happy=None, sleepy=None, sneezy=None): loc = locals() for key, val in loc.items(): if val is None: loc[key] = getattr(self, key) In fact, I do not have a strict opinion on this matter. And I'd rather be glad that PŠ½thon was less dynamic in some moments in favor of some optimizations. With kind regards, -gdg -- https://mail.python.org/mailman/listinfo/python-list
