Hi all,
I'd like to announce a new PEP.
It is mainly codifying that Python should do what you probably already
thought it did :)
Should be uncontroversial, but all comments are welcome.
Cheers,
Mark.
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…
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
Everyone,
If you've commented and you're worried you haven't been heard, please add
your issue *concisely* to this new thread. Note that the following issues
are already open and will be responded to separately; please don't bother
commenting on these until we've done so:
- Alternative spellings for '|'
- Whether to add an 'else' clause (and how to indent it)
- A different token for wildcards instead of '_'
- What to do about the footgun of 'case foo' vs. 'case .foo'
(Note that the last two could be combined, e.g. '?foo' or 'foo?' to mark a
variable binding and '?' for a wildcard.)
--
--Guido van Rossum (python.org/~guido)
*Pronouns: he/him **(why is my pronoun here?)*
<http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-…>
I have problem with the location of hexadecimal memory address in custom
reprs.
<threading.BoundedSemaphore: 2/3 at 0x7ff4c26b3eb0>
vs
<threading.BoundedSemaphore at 0x7ff4c26b3eb0: 2/3>
The long hexadecimal number makes the repr longer and distracts
attention from other useful information. We could get rid of it, but it
is useful if we want to distinguish objects of the same type. Although
it is hard to distinguish long hexadecimal numbers which differ only by
few digits in the middle.
What if use serial numbers to differentiate instances?
<threading.BoundedSemaphore #5: 2/3>
where the serial number starts with 1 and increased for every new
instance of that type.
The advantages are:
* Shorter repr.
* Easier to distinguish different objects.
* The serial number is unique for the life of program and cannot be
reused (in contrary to id/memory address).
The disadvantages are:
* Increased object size and creation time.
I do not propose to use serial numbers for all objects, because it would
increase the size of objects and the fixed-size integer can be
overflowed for some short-living objects created in mass (like numbers,
strings, tuples). But only for some custom objects implemented in
Python, for which size and creation time are not critical. I want to
start with synchronization objects in threading and multiprocessing
which did not have custom reprs, than change reprs of locks and asyncio
objects.
Is it worth to do?
> On 25 Jul 2020, at 03:44, Rob Cliffe <rob.cliffe(a)btinternet.com> wrote:
>
> Without arguing for or against allowing a capture variable, IMO rather
> than syntax like
> match <expr> into <var>:
> it would be far better (and not require a new keyword) to write this as
> with <var> as match <expr>:
>
> On 24/06/2020 20:38, Guido van Rossum wrote:
>> Everyone,
>>
>> If you've commented and you're worried you haven't been heard, please=20
>> add your issue *concisely* to this new thread. Note that the following=20
>> issues are already open and will be responded to separately; please=20
>> don't bother commenting on these until we've done so:
>>
>> - Alternative spellings for '|'
>> - Whether to add an 'else' clause (and how to indent it)
>> - A different token for wildcards instead of '_'
>> - What to do about the footgun of 'case foo' vs. 'case .foo'
>>
>> (Note that the last two could be combined, e.g. '?foo' or 'foo?' to=20
>> mark a variable binding and '?' for a wildcard.)
>>
We already have 'with' for contexts.
We already have patterns with 'as':
- except expression "as" identifier ":"
- "import" module "as" identifier
- "with" expression "as" target
So I think this would be quite confusing.
> On 25 Jul 2020, at 03:44, Rob Cliffe <rob.cliffe(a)btinternet.com> wrote:
>
> Without arguing for or against allowing a capture variable, IMO rather
> than syntax like
> match <expr> into <var>:
> it would be far better (and not require a new keyword) to write this as
> with <var> as match <expr>:
>
> On 24/06/2020 20:38, Guido van Rossum wrote:
>> Everyone,
>>
>> If you've commented and you're worried you haven't been heard, please=20
>> add your issue *concisely* to this new thread. Note that the following=20
>> issues are already open and will be responded to separately; please=20
>> don't bother commenting on these until we've done so:
>>
>> - Alternative spellings for '|'
>> - Whether to add an 'else' clause (and how to indent it)
>> - A different token for wildcards instead of '_'
>> - What to do about the footgun of 'case foo' vs. 'case .foo'
>>
>> (Note that the last two could be combined, e.g. '?foo' or 'foo?' to=20
>> mark a variable binding and '?' for a wildcard.)
>>
We already have 'with' for contexts.
We already have patterns with 'as':
- except expression "as" identifier ":"
- "import" module "as" identifier
- "with" expression "as" target
So I think this would be quite confusing.
Hi, all
There is a request to run python in a Linux-based embedded resource constrained system with sqlite3 support.
So many features are not required, like posixmodule, signalmodule, hashtable ...
But seems there are some dependencies among the Modules/Parser/Python/Objects/Programs...
Is there a way to tailor CPython 3 to a minimal set with sqlite3 (the less syscalls the better) ?
Is it possible to do that?
Thank you.
Hi,
A few weeks ago, I suggested adding mimetypes.mimesniff on stdlib.
(https://bugs.python.org/issue40841,
https://github.com/python/cpython/pull/20720)
Detecting MIME types well is an important feature and we already have
mimetypes detection library but AFAIK it is not good enough.
Note that some of our stdlib module already use the sniffing algorithm
(e.g imghdr)
The question is how exactly the mime sniffing should be done in terms
of file formats and algorithm. Luckily, WHATWG published the standard
for mime sniffing, and I think we should follow it.
(https://mimesniff.spec.whatwg.org/)
So I created the issue on the bpo and implemented it.
I 'd like to listen to all your opinions :)
--
Software Development Engineer at Kakao corp.
Tel: +82 10-3353-9127
Email: donghee.na92(a)gmail.com | denny.i(a)kakaocorp.com
Linkedin: https://www.linkedin.com/in/dong-hee-na-2b713b49/
