On Wed, 6 Jul 2016 02:13 am, eryk sun wrote:
> On Tue, Jul 5, 2016 at 3:50 PM, Steven D'Aprano
> wrote:
>> It works with exec:
[...]
> No, actually it doesn't work. Remember that when you store to a
> variable, it's implicitly a local variable, for which CPython uses
> STORE_NAME in unoptimized c
On Tue, Jul 5, 2016 at 4:12 PM, Random832 wrote:
> So any special logic in your own __setitem__, which may have
> included e.g. copying it to an alternate place, changing the key or
> value, or simply refusing to add the item to the dictionary at all, will
> be ignored, and your object may end up
On Tue, Jul 5, 2016 at 3:50 PM, Steven D'Aprano wrote:
> It works with exec:
>
> py> from collections import ChainMap
> py> class ChainDict(ChainMap, dict):
> ... pass
> ...
> py> m = ChainDict()
> py> exec("x = 1", m, m)
> py> m['x']
> 1
>
> (Tested in both 3.3 and 3.6.)
No, actually it does
On Tue, Jul 5, 2016, at 11:50, Steven D'Aprano wrote:
> If PyDict_SetItem expects an actual dict (accept no substitutes or
> subclasses), why is there no error? I would have expected a segfault at
> worst or at least an exception.
Subclasses are fine. Sort of. In general if you pass a *subclass* o
On Tue, Jul 5, 2016 at 3:37 PM, eryk sun wrote:
> In CPython 3.6, LOAD_GLOBAL does fall back on PyObject_GetItem
I did some digging to find when this changed in 3.3:
https://hg.python.org/cpython/diff/e3ab8aa0216c/Python/ceval.c
Notice in the last comment on issue 14385 that Martijn wanted to
u
On Wed, 6 Jul 2016 01:27 am, eryk sun wrote:
> On Tue, Jul 5, 2016 at 2:46 PM, Steven D'Aprano
> wrote:
>> I've come across two curious behaviours of a function using custom
>> globals. In both cases, I have a function where __globals__ is set to a
>> ChainMap.
>
> ChainMap implements the Mutabl
On Tue, Jul 5, 2016 at 3:27 PM, eryk sun wrote:
> ChainMap implements the MutableMapping abstract base class. But
> CPython needs globals to be a dict. In the current implementation,
> LOAD_GLOBAL calls _PyDict_LoadGlobal, and STORE_GLOBAL calls
> PyDict_SetItem. They don't fall back on the abstra
On Tue, Jul 5, 2016 at 2:46 PM, Steven D'Aprano wrote:
> I've come across two curious behaviours of a function using custom globals.
> In both cases, I have a function where __globals__ is set to a ChainMap.
ChainMap implements the MutableMapping abstract base class. But
CPython needs globals to
