On Sun, Jan 6, 2019 at 11:06 PM Steven D'Aprano wrote:
> I'm not wedded to the idea that the default ought to be the current
> behaviour. If there is a strong argument for one of the others, I'm
> listening.
"Errors should never pass silently"? Silently returning nonsensical
results is hard to de
On Sun, Jan 06, 2019 at 07:40:32PM -0800, Stephan Hoyer wrote:
> On Sun, Jan 6, 2019 at 4:27 PM Steven D'Aprano wrote:
>
> > I propose adding a "nan_policy" keyword-only parameter to the relevant
> > statistics functions (mean, median, variance etc), and defining the
> > following policies:
> >
>
I think the main issue is this: exception handling is already problematic
with its nonlocal transfer of control. Making it bidirectional makes code
even more difficult to understand. State will change "under your feet"
without any syntactic clue.
In "The Design and Evolution of C++" Bjarne Stroust
On Mon, Jan 7, 2019 at 1:27 AM Steven D'Aprano wrote:
> > In [4]: statistics.median([9, 9, 9, nan, 1, 2, 3, 4, 5])
> > Out[4]: 1
> > In [5]: statistics.median([9, 9, 9, nan, 1, 2, 3, 4])
> > Out[5]: nan
>
> The second is possibly correct if one thinks that the median of a list
> containing NAN sh
On Sun, Jan 06, 2019 at 10:52:47PM -0500, David Mertz wrote:
> Playing with Tim's examples, this suggests that statistics.median() is
> simply outright WRONG. I can think of absolutely no way to characterize
> these as reasonable results:
>
> Python 3.7.1 | packaged by conda-forge | (default, No
[David Mertz ]
> OK, let me be more precise. Obviously if the implementation in a class is:
>
> class Foo:
> def __lt__(self, other):
> return random.random() < 0.5
>
> Then we aren't going to rely on much.
>
> * If comparison of any two items in a list (under __lt__) is deterministic,
This statement is certainly false:
>
> * If two items are equal, and pairwise inequality is deterministic,
> exchanging the items does not affect the sorting of other items in the list.
>
Just to demonstrate this obviousness:
>>> sorted([9, 9, 9, b, 1, 2, 3, a])
[1, 2, 3, A, B, 9, 9, 9]
>>> sor
On Mon, Jan 7, 2019 at 3:19 PM David Mertz wrote:
>
> OK, let me be more precise. Obviously if the implementation in a class is:
>
> class Foo:
> def __lt__(self, other):
> return random.random() < 0.5
>
>
> Then we aren't going to rely on much.
>
> * If comparison of any two items in
OK, let me be more precise. Obviously if the implementation in a class is:
class Foo:
def __lt__(self, other):
return random.random() < 0.5
Then we aren't going to rely on much.
* If comparison of any two items in a list (under __lt__) is deterministic,
is the resulting sort order
[David Mertz ]
> Thanks Tim for clarifying. Is it even the case that sorts are STABLE in
> the face of non-total orderings under __lt__? A couple quick examples
> don't refute that, but what I tried was not very thorough, nor did I
> think much about TimSort itself.
I'm not clear on what "stable
[... apologies if this is dup, got a bounce ...]
> [David Mertz ]
>> I have to say though that the existing behavior of
`statistics.median[_low|_high|]`
>> is SURPRISING if not outright wrong. It is the behavior in existing
Python,
>> but it is very strange.
>>
>> The implementation simply does w
[David Mertz ]
> I have to say though that the existing behavior of
> `statistics.median[_low|_high|]`
> is SURPRISING if not outright wrong. It is the behavior in existing Python,
> but it is very strange.
>
> The implementation simply does whatever `sorted()` does, which is an
> implementation
On Sun, Jan 6, 2019 at 4:27 PM Steven D'Aprano wrote:
> I propose adding a "nan_policy" keyword-only parameter to the relevant
> statistics functions (mean, median, variance etc), and defining the
> following policies:
>
> IGNORE: quietly ignore all NANs
> FAIL: raise an exception if an
On 1/6/19 9:54 PM, simon.bordeyne wrote:
> I knew that you can just chain try/except blocks, and it's how I do it
> now, but the example I provided wasn't very realistic.
>
> Take for example the initialization of a class from a config file,
> config file which may or may not have certain keys in i
I knew that you can just chain try/except blocks, and it's how I do it now, but
the example I provided wasn't very realistic.
Take for example the initialization of a class from a config file, config file
which may or may not have certain keys in it. With many keys, it is very
inconvenient to ch
I have to say though that the existing behavior of
`statistics.median[_low|_high|]` is SURPRISING if not outright wrong. It
is the behavior in existing Python, but it is very strange.
The implementation simply does whatever `sorted()` does, which is an
implementation detail. In particular, NaN's
On Sun, Jan 06, 2019 at 07:46:03PM -0500, David Mertz wrote:
> Would these policies be named as strings or with an enum? Following Pandas,
> we'd probably support both.
Sure, I can support both.
> I won't bikeshed the names, but they seem to
> cover desired behaviors.
Good to hear.
--
Stev
Would these policies be named as strings or with an enum? Following Pandas,
we'd probably support both. I won't bikeshed the names, but they seem to
cover desired behaviors.
On Sun, Jan 6, 2019, 7:28 PM Steven D'Aprano Bug #33084 reports that the statistics library calculates median and
> other s
Bug #33084 reports that the statistics library calculates median and
other stats wrongly if the data contains NANs. Worse, the result depends
on the initial placement of the NAN:
py> from statistics import median
py> NAN = float('nan')
py> median([NAN, 1, 2, 3, 4])
2
py> median([1, 2, 3, 4, NAN]
There is already a much simpler way of doing this:
> try:
> i = int("string")
> except ValueError as e:
> print(e)
> print("continued on")
> j = int(9.0)
>
> The point of the 'try' block is to encapsulate the code you want to *stop*
> executing if an exception is ra
Eric V. Smith wrote:
> If the locale character is "*", use locale-aware formatting for the
> given "type", with LC_NUMERIC. So, "*g" would be equivalent to the
> existing "n", and "*f" would give you the current "f" formatting, except
> using LC_NUMERIC for the decimal point. If the locale cha
On Sat, Jan 5, 2019 at 4:39 PM Simon wrote:
> I propose to be able to use the continue keyword to continue the execution
> of the try block even when an error is handled. The above could then be
> changed to :
>
>
> try:
> i = int("string")
> print("continued on")
> j
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