[Python-Dev] Re: Function suggestion: itertools.one()
I'm sorry, I don't think I got that. I don't find a mailing list called itertools-ideas. Do you mean this should go to python-ideas? If so, I'm sorry for bothering python-dev, and I'll move this to python-ideas. I just read "The python-ideas list is for discussing more speculative design ideas" (https://www.python.org/community/lists/) as meaning discussing ideas for significant design changes, and not for adding a small function. Thanks, Noam > ___ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-le...@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/67MPZN4ZB7JXR47HGJWW66TIJCOQ4AEZ/ Code of Conduct: http://python.org/psf/codeofconduct/
[Python-Dev] Re: PEP 626: Precise line numbers for debugging and other tools.
On 25Jul2020 2014, Jim J. Jewett wrote: But it sounds as though you are saying the benefit is irrelevant; it is just inherently too expensive to ask programs that are already dealing with internals and trying to optimize performance to make a mechanical change from: code.magic_attrname to: magicdict[code] What have I missed? You've missed that debugging and profiling tools that operate purely on native memory can't execute Python code, so the "magic" has to be easily representable in C such that it can be copied into whichever language is being used (whether it's C, C++, C#, Rust, or something else). Cheers, Steve ___ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-le...@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/PE44CTX6NG6KOUPIJUFRXJHNFSFMN2TK/ Code of Conduct: http://python.org/psf/codeofconduct/
[Python-Dev] Re: Function suggestion: itertools.one()
For ideas like this it is best to discuss them on python-ideas.
I'll also mention that this idea has been brought up at least twice before:
search for threads about itertools and single() or first() (if I remember
correctly).
On Mon, Jul 27, 2020 at 12:07 PM Noam Yorav-Raphael
wrote:
> Hi,
>
> There's a simple function that I use many times, and I think may be a good
> fit to be added to itertools. A function that gets an iterator, and if it
> has exactly one element returns it, and otherwise raises an exception. This
> is very useful for cases where I do some sort of query that I expect to get
> exactly one result, and I want an exception to be raised if I'm wrong. For
> example:
>
> jack = one(p for p in people if p.id == '1234')
>
> sqlalchemy already has such a function for queries:
> https://docs.sqlalchemy.org/en/13/orm/query.html#sqlalchemy.orm.query.Query.one
>
> This is my implementation:
>
> def one(iterable):
> it = iter(iterable)
> try:
> r = next(it)
> except StopIteration:
> raise ValueError("Iterator is empty")
> try:
> next(it)
> except StopIteration:
> return r
> else:
> raise ValueError("Iterator has more than one item")
>
> What do you think?
>
> Thanks,
> Noam
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[Python-Dev] Re: Function suggestion: itertools.one()
On Tue, 28 Jul 2020 at 15:16, Brett Cannon wrote:
> For ideas like this it is best to discuss them on python-ideas.
>
> I'll also mention that this idea has been brought up at least twice
> before: search for threads about itertools and single() or first() (if I
> remember correctly).
>
I think "first" even passed "general approval' last time around (about 1
month ago) - but I can't recall if someone
took the responsibility of carrying that forward.
>
> On Mon, Jul 27, 2020 at 12:07 PM Noam Yorav-Raphael
> wrote:
>
>> Hi,
>>
>> There's a simple function that I use many times, and I think may be a
>> good fit to be added to itertools. A function that gets an iterator, and if
>> it has exactly one element returns it, and otherwise raises an exception.
>> This is very useful for cases where I do some sort of query that I expect
>> to get exactly one result, and I want an exception to be raised if I'm
>> wrong. For example:
>>
>> jack = one(p for p in people if p.id == '1234')
>>
>> sqlalchemy already has such a function for queries:
>> https://docs.sqlalchemy.org/en/13/orm/query.html#sqlalchemy.orm.query.Query.one
>>
>> This is my implementation:
>>
>> def one(iterable):
>> it = iter(iterable)
>> try:
>> r = next(it)
>> except StopIteration:
>> raise ValueError("Iterator is empty")
>> try:
>> next(it)
>> except StopIteration:
>> return r
>> else:
>> raise ValueError("Iterator has more than one item")
>>
>> What do you think?
>>
>> Thanks,
>> Noam
>> ___
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>> https://mail.python.org/archives/list/python-dev@python.org/message/D52MPKLIN4VEXBOCKVMTWAK66MAOEINY/
>> Code of Conduct: http://python.org/psf/codeofconduct/
>>
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[Python-Dev] Re: Function suggestion: itertools.one()
Thanks! I opened a new thread in python-ideas, here: https://mail.python.org/archives/list/python-id...@python.org/thread/6OLEL4XTUWXRI7ENODKEDOYFBRVDYKI7/ The "first" thread was very long, and was focused on a different function, first(). Perhaps a new thread, focused on one simple function in itertools, can reach a conclusion more easily. Thanks, Noam ___ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-le...@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/NK2ERT4Z3T2LLSMEHTAOMYJBLIDY7FTV/ Code of Conduct: http://python.org/psf/codeofconduct/
[Python-Dev] Re: PEP 626: Precise line numbers for debugging and other tools.
ah... we may have been talking past each other. Steve Dower wrote: > On 25Jul2020 2014, Jim J. Jewett wrote: > > But it sounds as though you are saying the benefit [of storing the line numbers in an external table, I thought, but perhaps Pablo Galindo Salgado and yourself were talking only of the switch from an lnotab string to an opaque co_linetable?] > > is irrelevant; it is just inherently too expensive to ask programs that are > > already dealing > > with internals and trying to optimize performance to make a mechanical > > change from: > > code.magic_attrname > > to: > > magicdict[code] > > What have I missed? > You've missed that debugging and profiling tools that operate purely on > native memory can't execute Python code, so the "magic" has to be easily > representable in C such that it can be copied into whichever language is > being used (whether it's C, C++, C#, Rust, or something else). Unless you really were talking only of the switch to co_linetable, I'm still missing the problem. To me, it still looks like a call to: PyAPI_FUNC(PyObject *) PyObject_GetAttrString(PyObject *, const char *); with the code object being stepped through and "co_lnotab" would be replaced by: PyAPI_FUNC(PyObject *) PyDict_GetItem(PyObject *mp, PyObject *key); using that same code object as the key, but getting the dict from some well-known (yet-to-be-defined) location, such as sys.code_to_lnotab. Mark Shannon and Carl Shapiro had seemed to object to the PEP because the new structure would make the code object longer, and making it smaller by a string does seem likely to be good. But if your real objections are to just to replacing the lnotab format with something that needs to be executed, then I apologize for misunderstanding. -jJ ___ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-le...@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/WUEFHFTPVTOPA3EFHACDECT3ZPLGGTFJ/ Code of Conduct: http://python.org/psf/codeofconduct/
