can't delete from a dictionary in a loop

[castironpi]

On May 16, 4:51 pm, Hans Nowak <zephyrfalcon!NO_SP... at gmail.com>
wrote:
> bruno.desthuilli... at gmail.com wrote:
> > On 16 mai, 23:34, "bruno.desthuilli... at gmail.com"
> > <bruno.desthuilli... at gmail.com> wrote:
> >> On 16 mai, 23:28, Hans Nowak <zephyrfalcon!NO_SP... at gmail.com> wrote:
>
> >>> Dan Upton wrote:
> >>>> for pid in procs_dict:
> > (snip)
> >>>    for pid in procs_dict.keys():
> >> I'm afraid this will do the same exact thing. A for loop on a dict
> >> iterates over the dict keys, so both statements are strictly
> >> equivalent from a practical POV.
>
> > Hem. Forget it. I should think twice before posting - this will
> > obviously make a big difference here.  Sorry for the noise.
>
> :-)  It appears that you would be right if this was Python 3.0, though:
>
> Python 3.0a5 (r30a5:62856, May 16 2008, 11:43:33)
> [GCC 4.0.1 (Apple Computer, Inc. build 5367)] on darwin
> Type "help", "copyright", "credits" or "license" for more information.
>  >>> d = {1: 2, 3: 4, 5: 6}
>  >>> for i in d.keys(): del d[i]
> ...
> Traceback (most recent call last):
>    File "<stdin>", line 1, in <module>
> RuntimeError: dictionary changed size during iteration
>
> Maybe 'for i in d' and 'for i in d.keys()' *are* functionally equivalent in 3.0,
> as d.keys() returns an object that iterates over d's keys... but I haven't read
> enough about it yet to be sure.  In any case, the problem goes away when we
> force a list:
>
>  >>> d = {1: 2, 3: 4, 5: 6}
>  >>> for i in list(d.keys()): del d[i]
> ...
>  >>> d
> {}
>
> --Hans- Hide quoted text -
>
> - Show quoted text -

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for i in d.keys()[:]:
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