Mailman 3 April 2021 - Python-Dev

Mixed Python/C debugging
by Skip Montanaro April 26, 2023

April 26, 2023

Having tried comp.lang.python with no response, I turn here... After at least ten years away from Python's run-time interpreter & byte code compiler, I'm getting set to familiarize myself with that again. This will, I think, entail debugging a mixed Python/C environment. I'm an Emacs user and am aware that GDB since 7.0 has support for debugging at the Python code level. Is Emacs+GDB my best bet? Are there any Python IDEs which support C-level breakpoints and debugging? Thanks, Skip

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PEP 448 review
by Guido van Rossum March 29, 2023

March 29, 2023

I'm back, I've re-read the PEP, and I've re-read the long thread with "(no subject)". I think Georg Brandl nailed it: """ *I like the "sequence and dict flattening" part of the PEP, mostly because itis consistent and should be easy to understand, but the comprehension syntaxenhancements seem to be bad for readability and "comprehending" what the codedoes.The call syntax part is a mixed bag on the one hand it is nice to be consistent with the extended possibilities in literals (… [View More]flattening), but on the other hand there would be small but annoying inconsistencies anyways (e.g. the duplicate kwarg case above).* """ Greg Ewing followed up explaining that the inconsistency between dict flattening and call syntax is inherent in the pre-existing different rules for dicts vs. keyword args: {'a':1, 'a':2} results in {'a':2}, while f(a=1, a=2) is an error. (This form is a SyntaxError; the dynamic case f(a=1, **{'a': 1}) is a TypeError.) For me, allowing f(*a, *b) and f(**d, **e) and all the other combinations for function calls proposed by the PEP is an easy +1 -- it's a straightforward extension of the existing pattern, and anybody who knows what f(x, *a) does will understand f(x, *a, y, *b). Guessing what f(**d, **e) means shouldn't be hard either. Understanding the edge case for duplicate keys with f(**d, **e) is a little harder, but the error messages are pretty clear, and it is not a new edge case. The sequence and dict flattening syntax proposals are also clean and logical -- we already have *-unpacking on the receiving side, so allowing *x in tuple expressions reads pretty naturally (and the similarity with *a in argument lists certainly helps). From here, having [a, *x, b, *y] is also natural, and then the extension to other displays is natural: {a, *x, b, *y} and {a:1, **d, b:2, **e}. This, too, gets a +1 from me. So that leaves comprehensions. IIRC, during the development of the patch we realized that f(*x for x in xs) is sufficiently ambiguous that we decided to disallow it -- note that f(x for x in xs) is already somewhat of a special case because an argument can only be a "bare" generator expression if it is the only argument. The same reasoning doesn't apply (in that form) to list, set and dict comprehensions -- while f(x for x in xs) is identical in meaning to f((x for x in xs)), [x for x in xs] is NOT the same as [(x for x in xs)] (that's a list of one element, and the element is a generator expression). The basic premise of this part of the proposal is that if you have a few iterables, the new proposal (without comprehensions) lets you create a list or generator expression that iterates over all of them, essentially flattening them: >>> xs = [1, 2, 3] >>> ys = ['abc', 'def'] >>> zs = [99] >>> [*xs, *ys, *zs] [1, 2, 3, 'abc', 'def', 99] >>> But now suppose you have a list of iterables: >>> xss = [[1, 2, 3], ['abc', 'def'], [99]] >>> [*xss[0], *xss[1], *xss[2]] [1, 2, 3, 'abc', 'def', 99] >>> Wouldn't it be nice if you could write the latter using a comprehension? >>> xss = [[1, 2, 3], ['abc', 'def'], [99]] >>> [*xs for xs in xss] [1, 2, 3, 'abc', 'def', 99] >>> This is somewhat seductive, and the following is even nicer: the *xs position may be an expression, e.g.: >>> xss = [[1, 2, 3], ['abc', 'def'], [99]] >>> [*xs[:2] for xs in xss] [1, 2, 'abc', 'def', 99] >>> On the other hand, I had to explore the possibilities here by experimenting in the interpreter, and I discovered some odd edge cases (e.g. you can parenthesize the starred expression, but that seems a syntactic accident). All in all I am personally +0 on the comprehension part of the PEP, and I like that it provides a way to "flatten" a sequence of sequences, but I think very few people in the thread have supported this part. Therefore I would like to ask Neil to update the PEP and the patch to take out the comprehension part, so that the two "easy wins" can make it into Python 3.5 (basically, I am accepting two-thirds of the PEP :-). There is some time yet until alpha 2. I would also like code reviewers (Benjamin?) to start reviewing the patch <http://bugs.python.org/issue2292>, taking into account that the comprehension part needs to be removed. -- --Guido van Rossum (python.org/~guido) [View Less]

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PEP 638: Syntactic macros
by Mark Shannon Feb. 5, 2023

Feb. 5, 2023

Hi everyone, I've submitted my PEP on syntactic macros as PEP 638. https://www.python.org/dev/peps/pep-0638/ All comments and suggestions are welcome. Cheers, Mark

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How about using modern C++ in development of CPython ?
by redradist＠gmail.com Oct. 19, 2022

Oct. 19, 2022

Hi all, What about of using modern C++ in developing CPython ? With C++ we can get the following benefits: 1) Readability - less code, most code is hidden by abstraction without losing performance 2) Maintainability - no code duplication in favor of using reusable classes 3) RAII - Resource Acquisition Is Initialization, predictable allocation and free resources ...

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PEP 563 and Python 3.10.
by Thomas Wouters July 22, 2022

July 22, 2022

(Starting a new thread so as not to derail any of the ongoing discussions.) Thanks, everyone, for your thoughts on Python 3.10 and the impact of PEP 563 (postponed evaluation of annotations) becoming the default. The Steering Council has considered the issue carefully, along with many of the proposed alternatives and solutions, and we’ve decided that at this point, we simply can’t risk the compatibility breakage of PEP 563. We need to roll back the change that made stringified annotations the … [View More]default, at least for 3.10. (Pablo is already working on this.) To be clear, we are not reverting PEP 563 itself. The future import will keep working like it did since Python 3.7. We’re delaying making PEP 563 string-based annotations the default until Python 3.11. This will give us time to find a solution that works for everyone (or to find a feasible upgrade path for users who currently rely on evaluated annotations). Some considerations that led us to this decision: - PEP 563’s default change is clearly too disruptive to downstream users and third-party libraries to happen right now. We can’t risk breaking even a small subset of the FastAPI/pydantic users, not to mention other uses of evaluated type annotations that we’re not aware of yet. - PEP 563 provides no warning to users of the feature it’s disabling. Without that, we can’t expect users to be aware of the upcoming breakage. The lack of a warning was by design, and made sense in a world where type annotations were only consumed by static type checkers --- but that’s not actually the situation we’re in. There are clearly existing real-world, run-time uses of type annotations that would be adversely affected by this change. - Originally, PEP 563 was scheduled to take effect in Python 4, and this changed recently (after the discussion in the Language Summit of 2020). It's possible that third-party libraries and users didn’t plan to react in the current time frame as they were not aware of this change in timing. - There isn’t enough time to properly discuss PEP 649 or any of the alternatives before the beta 1 deadline, and we really need to make sure we don’t compound errors here. We need to look for a long term solution, which isn’t possible while still maintaining the release deadlines of Python 3.10. That means we’re also deferring PEP 649 to Python 3.11. In the Steering Council’s unanimous opinion, rolling back the default flip for stringified annotations in Python 3.10 is the least disruptive of all the options. We need to continue discussing the issue and potential solutions, since this merely postpones the problem until 3.11. (For the record, postponing the change further is not off the table, either, for example if the final decision is to treat evaluated annotations as a deprecated feature, with warnings on use.) For what it’s worth, the SC is also considering what we can do to reduce the odds of something like this happening again, but that’s a separate consideration, and a multi-faceted one at that. For the Steering Council, Thomas. -- Thomas Wouters <thomas(a)python.org> Hi! I'm an email virus! Think twice before sending your email to help me spread! [View Less]

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PEP 651, Robust Stack Overflow Handling, Rejection notice
by Python Steering Council Jan. 31, 2022

Jan. 31, 2022

Hi Mark, Thank you for submitting PEP 651. The Steering Council has spent the past two weeks reviewing PEP 651. After careful consideration, we have decided to reject the PEP. The following were the key points that led us to this decision: * The benefits are not compelling enough. Deep recursion is not a common tool in Python, and even with PEP 651 it would not be efficient enough to make it a common tool. * The benefit of PEP 651 is negated as soon as a non-Python function is … [View More]

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PEP 646 (Variadic Generics): final call for comments
by Matthew Rahtz Jan. 18, 2022

Jan. 18, 2022

Hi everyone, We've got to the stage now with PEP 646 that we're feeling pretty happy with it. So far though we've mainly been workshopping it in typing-sig, so as PEP 1 requires we're asking for some feedback here too before submitting it to the steering council. If you have time over the next couple of weeks, please take a look at the current draft and let us know your thoughts: https://www.python.org/dev/peps/pep-0646/ (Note that the final couple of sections are out of date; https://github.… [View More]

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Deprecate Py_TRASHCAN_SAFE_BEGIN/END in 3.10?
by Irit Katriel Aug. 19, 2021

Aug. 19, 2021

Re https://bugs.python.org/issue40608. I think it will be an act of kindness to deprecate Py_TRASHCAN_SAFE_BEGIN/END in 3.10 and tell people to use Py_TRASHCAN_BEGIN/END instead. TL;DR: There was a change in 3.8 that introduced the latter while leaving the former for backwards compatibility, but also inadvertently breaking them. This is not an easy bug to deal with in the wild, we found it because we have a unit test in our codebase referencing https:// bugs.python.org/issue16602. A … [View More]

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Request for reviewers: pathlib improvements
by Barney Gale July 2, 2021

July 2, 2021

I’m working towards supporting subclassing pathlib.Path for things like zip/tar archives, iso files, S3, etc. This was first brought up a few years ago in bpo-24132 <https://bugs.python.org/issue24132> and discussed further on the python-ideas forum <https://discuss.python.org/t/make-pathlib-extensible/3428>. Before I can approach the meat of the issue, I'd like to land a handful of backwards-compatible patches that tidy up the pathlib internals. These are: - #19220 <https://… [View More]

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Speeding up CPython
by Mark Shannon May 18, 2021

May 18, 2021

Hi everyone, CPython is slow. We all know that, yet little is done to fix it. I'd like to change that. I have a plan to speed up CPython by a factor of five over the next few years. But it needs funding. I am aware that there have been several promised speed ups in the past that have failed. You might wonder why this is different. Here are three reasons: 1. I already have working code for the first stage. 2. I'm not promising a silver bullet. I recognize that this is a substantial amount … [View More]

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PEP 1, PEP Purpose and Guidelines
by barry＠zope.com May 18, 2021

May 18, 2021

It has been a while since I posted a copy of PEP 1 to the mailing lists and newsgroups. I've recently done some updating of a few sections, so in the interest of gaining wider community participation in the Python development process, I'm posting the latest revision of PEP 1 here. A version of the PEP is always available on-line at http://www.python.org/peps/pep-0001.html Enjoy, -Barry -------------------- snip snip -------------------- PEP: 1 Title: PEP Purpose and Guidelines Version: … [View More]$Revision: 1.36 $ Last-Modified: $Date: 2002/07/29 18:34:59 $ Author: Barry A. Warsaw, Jeremy Hylton Status: Active Type: Informational Created: 13-Jun-2000 Post-History: 21-Mar-2001, 29-Jul-2002 What is a PEP? PEP stands for Python Enhancement Proposal. A PEP is a design document providing information to the Python community, or describing a new feature for Python. The PEP should provide a concise technical specification of the feature and a rationale for the feature. We intend PEPs to be the primary mechanisms for proposing new features, for collecting community input on an issue, and for documenting the design decisions that have gone into Python. The PEP author is responsible for building consensus within the community and documenting dissenting opinions. Because the PEPs are maintained as plain text files under CVS control, their revision history is the historical record of the feature proposal[1]. Kinds of PEPs There are two kinds of PEPs. A standards track PEP describes a new feature or implementation for Python. An informational PEP describes a Python design issue, or provides general guidelines or information to the Python community, but does not propose a new feature. Informational PEPs do not necessarily represent a Python community consensus or recommendation, so users and implementors are free to ignore informational PEPs or follow their advice. PEP Work Flow The PEP editor, Barry Warsaw <peps(a)python.org>, assigns numbers for each PEP and changes its status. The PEP process begins with a new idea for Python. It is highly recommended that a single PEP contain a single key proposal or new idea. The more focussed the PEP, the more successfully it tends to be. The PEP editor reserves the right to reject PEP proposals if they appear too unfocussed or too broad. If in doubt, split your PEP into several well-focussed ones. Each PEP must have a champion -- someone who writes the PEP using the style and format described below, shepherds the discussions in the appropriate forums, and attempts to build community consensus around the idea. The PEP champion (a.k.a. Author) should first attempt to ascertain whether the idea is PEP-able. Small enhancements or patches often don't need a PEP and can be injected into the Python development work flow with a patch submission to the SourceForge patch manager[2] or feature request tracker[3]. The PEP champion then emails the PEP editor <peps(a)python.org> with a proposed title and a rough, but fleshed out, draft of the PEP. This draft must be written in PEP style as described below. If the PEP editor approves, he will assign the PEP a number, label it as standards track or informational, give it status 'draft', and create and check-in the initial draft of the PEP. The PEP editor will not unreasonably deny a PEP. Reasons for denying PEP status include duplication of effort, being technically unsound, not providing proper motivation or addressing backwards compatibility, or not in keeping with the Python philosophy. The BDFL (Benevolent Dictator for Life, Guido van Rossum) can be consulted during the approval phase, and is the final arbitrator of the draft's PEP-ability. If a pre-PEP is rejected, the author may elect to take the pre-PEP to the comp.lang.python newsgroup (a.k.a. python-list(a)python.org mailing list) to help flesh it out, gain feedback and consensus from the community at large, and improve the PEP for re-submission. The author of the PEP is then responsible for posting the PEP to the community forums, and marshaling community support for it. As updates are necessary, the PEP author can check in new versions if they have CVS commit permissions, or can email new PEP versions to the PEP editor for committing. Standards track PEPs consists of two parts, a design document and a reference implementation. The PEP should be reviewed and accepted before a reference implementation is begun, unless a reference implementation will aid people in studying the PEP. Standards Track PEPs must include an implementation - in the form of code, patch, or URL to same - before it can be considered Final. PEP authors are responsible for collecting community feedback on a PEP before submitting it for review. A PEP that has not been discussed on python-list(a)python.org and/or python-dev(a)python.org will not be accepted. However, wherever possible, long open-ended discussions on public mailing lists should be avoided. Strategies to keep the discussions efficient include, setting up a separate SIG mailing list for the topic, having the PEP author accept private comments in the early design phases, etc. PEP authors should use their discretion here. Once the authors have completed a PEP, they must inform the PEP editor that it is ready for review. PEPs are reviewed by the BDFL and his chosen consultants, who may accept or reject a PEP or send it back to the author(s) for revision. Once a PEP has been accepted, the reference implementation must be completed. When the reference implementation is complete and accepted by the BDFL, the status will be changed to `Final.' A PEP can also be assigned status `Deferred.' The PEP author or editor can assign the PEP this status when no progress is being made on the PEP. Once a PEP is deferred, the PEP editor can re-assign it to draft status. A PEP can also be `Rejected'. Perhaps after all is said and done it was not a good idea. It is still important to have a record of this fact. PEPs can also be replaced by a different PEP, rendering the original obsolete. This is intended for Informational PEPs, where version 2 of an API can replace version 1. PEP work flow is as follows: Draft -> Accepted -> Final -> Replaced ^ +----> Rejected v Deferred Some informational PEPs may also have a status of `Active' if they are never meant to be completed. E.g. PEP 1. What belongs in a successful PEP? Each PEP should have the following parts: 1. Preamble -- RFC822 style headers containing meta-data about the PEP, including the PEP number, a short descriptive title (limited to a maximum of 44 characters), the names, and optionally the contact info for each author, etc. 2. Abstract -- a short (~200 word) description of the technical issue being addressed. 3. Copyright/public domain -- Each PEP must either be explicitly labelled as placed in the public domain (see this PEP as an example) or licensed under the Open Publication License[4]. 4. Specification -- The technical specification should describe the syntax and semantics of any new language feature. The specification should be detailed enough to allow competing, interoperable implementations for any of the current Python platforms (CPython, JPython, Python .NET). 5. Motivation -- The motivation is critical for PEPs that want to change the Python language. It should clearly explain why the existing language specification is inadequate to address the problem that the PEP solves. PEP submissions without sufficient motivation may be rejected outright. 6. Rationale -- The rationale fleshes out the specification by describing what motivated the design and why particular design decisions were made. It should describe alternate designs that were considered and related work, e.g. how the feature is supported in other languages. The rationale should provide evidence of consensus within the community and discuss important objections or concerns raised during discussion. 7. Backwards Compatibility -- All PEPs that introduce backwards incompatibilities must include a section describing these incompatibilities and their severity. The PEP must explain how the author proposes to deal with these incompatibilities. PEP submissions without a sufficient backwards compatibility treatise may be rejected outright. 8. Reference Implementation -- The reference implementation must be completed before any PEP is given status 'Final,' but it need not be completed before the PEP is accepted. It is better to finish the specification and rationale first and reach consensus on it before writing code. The final implementation must include test code and documentation appropriate for either the Python language reference or the standard library reference. PEP Template PEPs are written in plain ASCII text, and should adhere to a rigid style. There is a Python script that parses this style and converts the plain text PEP to HTML for viewing on the web[5]. PEP 9 contains a boilerplate[7] template you can use to get started writing your PEP. Each PEP must begin with an RFC822 style header preamble. The headers must appear in the following order. Headers marked with `*' are optional and are described below. All other headers are required. PEP: <pep number> Title: <pep title> Version: <cvs version string> Last-Modified: <cvs date string> Author: <list of authors' real names and optionally, email addrs> * Discussions-To: <email address> Status: <Draft | Active | Accepted | Deferred | Final | Replaced> Type: <Informational | Standards Track> * Requires: <pep numbers> Created: <date created on, in dd-mmm-yyyy format> * Python-Version: <version number> Post-History: <dates of postings to python-list and python-dev> * Replaces: <pep number> * Replaced-By: <pep number> The Author: header lists the names and optionally, the email addresses of all the authors/owners of the PEP. The format of the author entry should be address(a)dom.ain (Random J. User) if the email address is included, and just Random J. User if the address is not given. If there are multiple authors, each should be on a separate line following RFC 822 continuation line conventions. Note that personal email addresses in PEPs will be obscured as a defense against spam harvesters. Standards track PEPs must have a Python-Version: header which indicates the version of Python that the feature will be released with. Informational PEPs do not need a Python-Version: header. While a PEP is in private discussions (usually during the initial Draft phase), a Discussions-To: header will indicate the mailing list or URL where the PEP is being discussed. No Discussions-To: header is necessary if the PEP is being discussed privately with the author, or on the python-list or python-dev email mailing lists. Note that email addresses in the Discussions-To: header will not be obscured. Created: records the date that the PEP was assigned a number, while Post-History: is used to record the dates of when new versions of the PEP are posted to python-list and/or python-dev. Both headers should be in dd-mmm-yyyy format, e.g. 14-Aug-2001. PEPs may have a Requires: header, indicating the PEP numbers that this PEP depends on. PEPs may also have a Replaced-By: header indicating that a PEP has been rendered obsolete by a later document; the value is the number of the PEP that replaces the current document. The newer PEP must have a Replaces: header containing the number of the PEP that it rendered obsolete. PEP Formatting Requirements PEP headings must begin in column zero and the initial letter of each word must be capitalized as in book titles. Acronyms should be in all capitals. The body of each section must be indented 4 spaces. Code samples inside body sections should be indented a further 4 spaces, and other indentation can be used as required to make the text readable. You must use two blank lines between the last line of a section's body and the next section heading. You must adhere to the Emacs convention of adding two spaces at the end of every sentence. You should fill your paragraphs to column 70, but under no circumstances should your lines extend past column 79. If your code samples spill over column 79, you should rewrite them. Tab characters must never appear in the document at all. A PEP should include the standard Emacs stanza included by example at the bottom of this PEP. A PEP must contain a Copyright section, and it is strongly recommended to put the PEP in the public domain. When referencing an external web page in the body of a PEP, you should include the title of the page in the text, with a footnote reference to the URL. Do not include the URL in the body text of the PEP. E.g. Refer to the Python Language web site [1] for more details. ... [1] http://www.python.org When referring to another PEP, include the PEP number in the body text, such as "PEP 1". The title may optionally appear. Add a footnote reference that includes the PEP's title and author. It may optionally include the explicit URL on a separate line, but only in the References section. Note that the pep2html.py script will calculate URLs automatically, e.g.: ... Refer to PEP 1 [7] for more information about PEP style ... References [7] PEP 1, PEP Purpose and Guidelines, Warsaw, Hylton http://www.python.org/peps/pep-0001.html If you decide to provide an explicit URL for a PEP, please use this as the URL template: http://www.python.org/peps/pep-xxxx.html PEP numbers in URLs must be padded with zeros from the left, so as to be exactly 4 characters wide, however PEP numbers in text are never padded. Reporting PEP Bugs, or Submitting PEP Updates How you report a bug, or submit a PEP update depends on several factors, such as the maturity of the PEP, the preferences of the PEP author, and the nature of your comments. For the early draft stages of the PEP, it's probably best to send your comments and changes directly to the PEP author. For more mature, or finished PEPs you may want to submit corrections to the SourceForge bug manager[6] or better yet, the SourceForge patch manager[2] so that your changes don't get lost. If the PEP author is a SF developer, assign the bug/patch to him, otherwise assign it to the PEP editor. When in doubt about where to send your changes, please check first with the PEP author and/or PEP editor. PEP authors who are also SF committers, can update the PEPs themselves by using "cvs commit" to commit their changes. Remember to also push the formatted PEP text out to the web by doing the following: % python pep2html.py -i NUM where NUM is the number of the PEP you want to push out. See % python pep2html.py --help for details. Transferring PEP Ownership It occasionally becomes necessary to transfer ownership of PEPs to a new champion. In general, we'd like to retain the original author as a co-author of the transferred PEP, but that's really up to the original author. A good reason to transfer ownership is because the original author no longer has the time or interest in updating it or following through with the PEP process, or has fallen off the face of the 'net (i.e. is unreachable or not responding to email). A bad reason to transfer ownership is because you don't agree with the direction of the PEP. We try to build consensus around a PEP, but if that's not possible, you can always submit a competing PEP. If you are interested assuming ownership of a PEP, send a message asking to take over, addressed to both the original author and the PEP editor <peps(a)python.org>. If the original author doesn't respond to email in a timely manner, the PEP editor will make a unilateral decision (it's not like such decisions can be reversed. :). References and Footnotes [1] This historical record is available by the normal CVS commands for retrieving older revisions. For those without direct access to the CVS tree, you can browse the current and past PEP revisions via the SourceForge web site at http://cvs.sourceforge.net/cgi-bin/cvsweb.cgi/python/nondist/peps/?cvsroot=… [2] http://sourceforge.net/tracker/?group_id=5470&atid=305470 [3] http://sourceforge.net/tracker/?atid=355470&group_id=5470&func=browse [4] http://www.opencontent.org/openpub/ [5] The script referred to here is pep2html.py, which lives in the same directory in the CVS tree as the PEPs themselves. Try "pep2html.py --help" for details. The URL for viewing PEPs on the web is http://www.python.org/peps/ [6] http://sourceforge.net/tracker/?group_id=5470&atid=305470 [7] PEP 9, Sample PEP Template http://www.python.org/peps/pep-0009.html Copyright This document has been placed in the public domain. Local Variables: mode: indented-text indent-tabs-mode: nil sentence-end-double-space: t fill-column: 70 End: [View Less]

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On the migration from master to main
by Python Steering Council May 10, 2021

May 10, 2021

From Thomas Wouters, on behalf of and with full support of the Python Steering Council: This discussion seems to have died down a little, but I still want to make a few things clear: Yes, this is a political decision. Very many decisions are political. The existence of an open-source project is inherently political. The decision to try and make python-dev more welcoming, more open, more helpful is also a political decision -- one that the SC feels is absolutely necessary for the long-term … [View More]

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PEP 654: Exception Groups and except* [REPOST]
by Irit Katriel May 6, 2021

May 6, 2021

We would like to present for feedback a new version of PEP 654, which incorporates the feedback we received in the discussions so far: https://www.python.org/dev/peps/pep-0654/ The reference implementation has also been updated along with the PEP. The changes we made since the first post are: 1. Instead of ExceptionGroup(BaseException), we will have two new builtin types: BaseExceptionGroup(BaseException) and ExceptionGroup(BaseExceptionGroup, Exception). This is so that "except Exception" … [View More]

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Anyone else gotten bizarre personal replies to mailing list posts?
by Nathaniel Smith May 4, 2021

May 4, 2021

I just got the reply below sent directly to my personal account, and I'm confused about what's going on. If it's just a one off I'll chalk it up to random internet weirdness, but if other folks are getting these too it might be something the list admins should look into? Or... something? ---------- Forwarded message --------- From: Hoi lam Poon <gillcovid19(a)gmail.com> Date: Fri, Apr 23, 2021, 02:01 Subject: Re: [Python-Dev] Re: PEP 654: Exception Groups and except* [REPOST] To: … [View More]Nathaniel Smith <njs(a)pobox.com> Stop pretending, I can definitely get the key control file, your working group, all past actions and instructions cannot be cleared in front of me at all. You have been playing around for a few days, and I won’t stop you. Your face? I won’t, you know, you can’t drive me away, and that file is all, after I get it, you will be convicted even if you disband, I swear 在 2021年4月23日週五 16:23，Nathaniel Smith <njs(a)pobox.com> 寫道： > On Wed, Apr 21, 2021 at 4:50 PM Guido van Rossum <guido(a)python.org> wrote: > > On Wed, Apr 21, 2021 at 3:26 PM Nathaniel Smith <njs(a)pobox.com> wrote: > >> Sure. This was in my list of reasons why the backwards compatibility > >> tradeoffs are forcing us into awkward compromises. I only elaborated > >> on it b/c in your last email you said you didn't understand why this > >> was a problem :-). And except* is definitely useful. But I think there > >> are options for 'except' that haven't been considered fully. > > > > Do you have any suggestions, or are you just telling us to think harder? > Because we've already thought as hard as we could and within all the > constraints (backwards compatibility and otherwise) we just couldn't think > of a better one. > > The main possibility that I don't think we've examined fully is to > make 'except' blocks fire multiple times when there are multiple > exceptions. We ruled it out early b/c it's incompatible with nested > EGs, but if flat EGs are better anyway, then the balance shifts around > and it might land somewhere different. it's a tricky discussion > though, b/c both the current proposal and the alternative have very > complex implications and downsides. So we probably shouldn't get too > distracted by that until after the flat vs nested discussion has > settled down more. > > I'm not trying to filibuster here -- I really want some form of EGs to > land. I think python has the potential to be the most elegant and > accessible language around for writing concurrent programs, and EGs > are a key part of that. I don't want to fight about anything; I just > want to work together to make sure we have a full picture of our > options, so we can be confident we're making the best choice. > > > The real cost here is that we would need a new "TracebackGroup" concept, > since the internal data structures and APIs keep the traceback chain and > the exception object separated until the exception is caught. In our early > design stages we actually explored this and the complexity of the data > structures was painful. We eventually realized that we didn't need this > concept at all, and the result is much clearer, despite what you seem to > think. > > I'm not talking about TracebackGroups (at least, I think I'm not?). I > think it can be done with exactly our current data structures, nothing > new. > > - When an EG is raised, build the traceback for just that EG while > it's unwinding. This means if any C code peeks at exc_info while it's > in flight, it'll only see the current branch of the traceback tree, > but that seems fine. > - When the exception is caught and we go to write back the traceback > to its __traceback__ attribute, instead "peek through" the EG and > append the built-up traceback entries onto each of the constituent > exceptions. > > You could get cleverer for efficiency, but that basic concept seems > pretty simple and viable to me. What am I missing? > > -n > > -- > Nathaniel J. Smith -- https://vorpus.org > _______________________________________________ > Python-Dev mailing list -- python-dev(a)python.org > To unsubscribe send an email to python-dev-leave(a)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/VOBOWZG… > Code of Conduct: http://python.org/psf/codeofconduct/ > [View Less]

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Existing asyncio features scheduled for removal in Python 3.9 and 3.10
by Illia Volochii May 2, 2021

May 2, 2021

Hi everyone, There are a couple of uncompleted asyncio feature removals scheduled for 3.9 and 3.10 releases. It will be great if we either complete them or reschedule before the 3.10 feature freeze. There are two stale pull requests related to this. Removal of @asyncio.coroutine in version 3.10 deprecated since version 3.8 Documentation: https://docs.python.org/3.10/library/asyncio-task.html#asyncio.coroutine Issue deprecating the decorator: https://bugs.python.org/issue36921 Issue for the … [View More]

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In what tense should the changelog be written?
by Larry Hastings May 1, 2021

May 1, 2021

When one writes one's "blurb" for the changelog, in what tense should it be? I mostly see entries in present tense: bpo-43660: Fix crash that happens when replacing sys.stderr with a callable that can remove the object while an exception is being printed. Patch by Pablo Galindo. bpo-41561: Add workaround for Ubuntu’s custom OpenSSL security level policy. But occasionally I see entries in past tense: bpo-26053: Fixed bug where the pdb interactive run command … [View More]

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Summary of Python tracker Issues
by Python tracker April 30, 2021

April 30, 2021

ACTIVITY SUMMARY (2021-04-23 - 2021-04-30) Python tracker at https://bugs.python.org/ To view or respond to any of the issues listed below, click on the issue. Do NOT respond to this message. Issues counts and deltas: open 7453 (-21) closed 48273 (+86) total 55726 (+65) Open issues with patches: 2968 Issues opened (48) ================== #42737: PEP 563: drop annotations for complex assign targets https://bugs.python.org/issue42737 reopened by BTaskaya #43926: Clean metadata (… [View More]

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SC feedback: PEP 648 -- Extensible customizations of the interpreter at startup
by Barry Warsaw April 30, 2021

April 30, 2021

Hello Mario, Thank you for your submission of PEP 648 (Extensible customizations of the interpreter at startup). The Python Steering Council has reviewed the PEP and before we can pronounce on it, we have some additional questions and comments we’d like you to address. Once these questions are settled, we are requesting that you post the PEP to python-dev for another round of comments. In general, the SC is in favor of deprecating the executable hack capabilities of pth files, and this PEP … [View More]is currently the most concrete proposal to get there. We would like to eventually go farther, including deprecation of pth files entirely, but that is outside the scope of this PEP. General PEP feedback The introduction of the section titled “Benefits of __sitecustomize__” seems out of place. It forward references the solution without explanation. It also says “The use of a __sitecustomize__ will allow…”; the question is, a __sitecustomize__ what? Directory? File? Perhaps it should be moved to later in the PEP after the semantics of __sitecustomize__ is defined? Some of the terminology used in the PEP could be clarified. For example, I suggest using the term “directory” instead of “folder” throughout the PEP, and use the term “module” or “file” instead of “script” to describe the things inside __sitecustomize__ directories that Python imports, since “scripts” typically describe standalone files that implement applications. For example, must the files be named with .py extension (or presumably .pyc, .pyo) under the normal Python module import rules? (Later in the PEP you do allude to the requirement that the file name must end in .py, but it would be much better to explain this right up front, in a formal specification.) Another ambiguity is what the PEP means by “executing” said “scripts”. Does that mean importing them? Reading them then exec()’ing them? Something else? This section should be clear that Python will import the modules it found, if that’s indeed what the PEP is proposing. The “Backward compatibility” section has this incomplete sentence: “Ignoring those lines in pth files.” There’s this odd grammar in the “Do nothing” section: “After analysing the impact of this change, we believe it is worth given the enhanced experience it brings.” Perhaps it should read “...it is worth it, given the…”? Definition of “site path” The PEP should precisely define what it means when it says “...a folder named __sitecustomize__ located in any site path”. What exactly is a “site path”? Is this any directory on sys.path? Is it a directory named site-packages? This phrase is also ambiguous: “As the folder will be within sys.path, given that it is located in site paths...”. “sys.path” isn’t a thing that can hold a folder, since it’s just a list of strings, and it also can get extended by any number of means, e.g. by setting the PYTHONPATH environment variable at interpreter startup time. So for example, how does PYTHONPATH affect the algorithm? What is the rationale for adding multiple __sitecustomize__ directories, rather than a single directory (or possibly two, one in Python’s system location and one in the user location)? This would simplify the discovery process, and tools like pip can warn the user if a name collision were to occur. I think the PEP needs to be much more crisp and precise in defining the when and how __sitecustomize__ directories are discovered at start up time. Order of Execution I think this section should outline the entire startup execution order. Exactly when do pth files still get evaluated in relationship to __sitecustomize__ discovery? How do pth file sys.path extensions affect the search for __sitecustomize__ directories? This section also says files in __sitecustomize__ will be executed in “file name sorted order”, but the PEP is unclear whether all such files found in every __sitecustomize__ directory will be sorted together, or only within a single __sitecustomize__ directory. Presumably file system encodings are used to determine file name sort order, but I think the PEP should be explicit about this. I’d like to see the execution order for the entire proposed new Python startup sequence as a recipe, or perhaps even some Python pseudo-code. Impact on startup time We still think that startup performance can be a concern. This section needs more data. For example, while the executable part of pth files is being deprecated, both pth and __sitecustomize__ modules will exist. How does this affect startup time in a world where both have to be discovered and processed? The PEP says: “If the user has custom scripts, we think that the impact on the performance of walking each of the folders is acceptable, as the user wants to use this feature.” Does the user really want to use this feature? Won’t it more likely be the system administrator or Python distribution and packaging ecosystem that chooses to use the __sitecustomize__ feature? Maybe the user won’t even know that it’s being used by the packages being installed? The PEP says: ““Running "./python -c pass" with perf on 50 iterations, repeating 50 times the command on each and getting the geometric mean on a commodity laptop did not reveal any substantial raise on CPU time.” We request more information on the experiments performed, and specific numbers so that the startup impact can be reproduced and confirmed by others. E.g. did you run this experiment on a branch of CPython 3.10 with the PEP 648 reference implementation? Did you convert existing uses of executable pth files to __sitecustomize__ modules? How many such modules did you try it with? How many __sitecustomize__ directories were in your tests? Other questions and issues How does this feature interact with virtual environments? What do packaging tools have to do to support this PEP? The PEP mentions setuptools, but what about other packaging tools in common use? The PEP says “This impact will be reduced in the future as we will remove two other imports: "sitecustomize.py" and "usercustomize.py”.” Why not explicitly deprecate these and executable pth files in PEP 648 and begin the countdown at the same time __sitecustomize__ is added to Python? The PEP says: “To facilitate debugging of the Python startup, a new option will be added to the main of the site module to list all scripts that will be executed as part of the __sitecustomize__ initialization.” The PEP should be explicit about what command line switch is being proposed. We think this should probably be an -X option. Do you have any concerns that this feature will be overused? Does separating the execution feature from the path extension feature make it more or less likely to be used by third party library authors? Will the runtime have any access to the list of __sitecustomize__ modules being executed? I.e. will you collect their paths in a new sys module attribute? Will there be any functions to import or list __sitecustomize__ directories or modules after start has completed? We think io.open_code() should be used so that reading the files can be audited. Conclusion The Python Steering Council again wants to thank you for your PEP contribution! We hope you find this feedback constructive and helpful. We look forward to your responses, and an updated PEP. Cheers, -Barry (on behalf of the Python Steering Council) [View Less]

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stdlib Flag Enums and the "no value" member
by Ethan Furman April 29, 2021

April 29, 2021

An excerpt from bpo-31369: re.RegexFlag and `__all__` GvR: ---- > One thing I discovered when developing this example: there doesn't seem to be a flag to > represent 0 (zero), i.e. "no flags". And foo(0) is a type error (even though it works > fine at runtime). Which raises the question: Do we want to have a standard name for stdlib Flags when no flags are set? What should we call it? - NONE - ZERO - EMPTY - ??? -- ~Ethan~

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PEP 652: Python 3.10 will have explicit Limited C API & Stable ABI
by Petr Viktorin April 29, 2021

April 29, 2021

Hello, I've merged the main part of PEP-652 implementation. The Limited C API (introduced in PEP 384 and used for extension modules that work across Python versions without recompilation) is now explicitly defined and better tested. When changing/extending the limited API: - Stop and think! This API will need to be suppported forever (or until Python 3 reaches end of life, if that comes sooner). A checklist of what to think about is being added to the devguide [0]. - Add/change an entry … [View More]

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expanduser('~other') reliability and future
by Barney Gale April 28, 2021

April 28, 2021

There’s been a bit of discussion on the reliability of getting other users' home directories via os.path.expanduser(), mostly on issue42998 <https://bugs.python.org/issue42998>. In msg390503 <https://bugs.python.org/issue42998#msg390503>, Serhiy Storchaka pointed out that ntpath only makes an educated guess of other user’s home directories. In msg390535 <https://bugs.python.org/issue42998#msg390535>, Eryk Sun supplied an improved ntpath implementation that makes use of … [View More]

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Revive PEP 396 -- Module Version Numbers ?
by Christopher Barker April 27, 2021

April 27, 2021

I've already asked on python-ideas, but it was suggested that as there's a PEP already, it's time to move this along. So here's the pitch. Over the years, I've seen __version__ used very broadly but not *quite* in all packages. I've always known it was a convention, not a requirement. But it turns out it's not even a "official" convention. But it really would be nice if there was a consistent way that I could count on to get the version of a package at run time from the package itself. Turns … [View More]

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bz2.BZ2File doesn't support name?
by roy＠panix.com April 27, 2021

April 27, 2021

I was surprised recently to discover that BZ2File (at least in 3.7) doesn't have a name attribute. Is there some fundamental reason name couldn't be supported, or is it just a bug that it wasn't implemented?

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Deferral of PEP 648 - Extensible customizations of the interpreter at startup
by Barry Warsaw April 27, 2021

April 27, 2021

Hi Mario, The Python Steering Council today decided that we will defer consideration of PEP 648 to Python 3.11. On March 30, 2021 we sent the following feedback to you via python-dev, which began a discussion thread: https://mail.python.org/archives/list/python-dev@python.org/message/OGYZZZ4… We on the SC extend our thanks again for the PEP, and encourage you to continue to work on this PEP for pronouncement in Python 3.11. Cheers, -Barry (on behalf of the Python Steering Council)

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How to keep Signaling NaN unchanged when convert hex to single-precision float ?
by Huang, Yang April 27, 2021

April 27, 2021

Hi, Code snippet 1 and 2 convert an hex to float, but the SNaN is changed to QNaN automatically. It follows IEEE 754 behavior. While Code snippet 3 converts an hex to double, and the SNaN keeps. Is there any solution to keep SNaN float unchanged in Code snippet 1 and 2? 1. >>> i = int('7f800001', 16) >>> cp = pointer(c_uint32(i)) >>> fp = cast(cp, POINTER(c_float)) >>> print(fp.contents.value) # nan >>> print(struct.pack(">f", fp.contents.… [View More]

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