GeezerVisonThe World Wide Web, restored to 800 pixels of glory. |
| Home|About|Gaming cabinet|Archives|How it works|Starter sites |
GeezerVison is showing mail.python.org — Mailman 3 August 2020 - Python-Dev - python.org Python-Dev
Threads by month
August 2020
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
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 (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)
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: $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:
In Python 2.5 `0or[]` was accepted by the Python parser. It became an
error in 2.6 because "0o" became recognizing as an incomplete octal
number. `1or[]` still is accepted.
On other hand, `1if 2else 3` is accepted despites the fact that "2e" can
be recognized as an incomplete floating point number. In this case the
tokenizer pushes "e" back and returns "2".
Shouldn't it do the same with "0o"? It is possible to make `0or[]` be
parseable again. Python implementation is able to tokenize this example:
$ echo '0or[]' | ./python -m tokenize
1,0-1,1: NUMBER '0'
1,1-1,3: NAME 'or'
1,3-1,4: OP '['
1,4-1,5: OP ']'
1,5-1,6: NEWLINE '\n'
2,0-2,0: ENDMARKER ''
On other hand, all these examples look weird. There is an assymmetry:
`1or 2` is a valid syntax, but `1 or2` is not. It is hard to recognize
visually the boundary between a number and the following identifier or
keyword, especially if numbers can contain letters ("b", "e", "j", "o",
"x") and underscores, and identifiers can contain digits. On both sides
of the boundary can be letters, digits, and underscores.
I propose to change the Python syntax by adding a requirement that there
should be a whitespace or delimiter between a numeric literal and the
following keyword.
Hi, folks.
Since the previous discussion was suspended without consensus, I wrote
a new PEP for it. (Thank you Victor for reviewing it!)
This PEP looks very similar to PEP 623 "Remove wstr from Unicode",
but for encoder APIs, not for Unicode object APIs.
URL (not available yet): https://www.python.org/dev/peps/pep-0624/
---
PEP: 624
Title: Remove Py_UNICODE encoder APIs
Author: Inada Naoki <songofacandy(a)gmail.com>
Status: Draft
Type: Standards Track
Content-Type: text/x-rst
Created: 06-Jul-2020
Python-Version: 3.11
Abstract
========
This PEP proposes to remove deprecated ``Py_UNICODE`` encoder APIs in
Python 3.11:
* ``PyUnicode_Encode()``
* ``PyUnicode_EncodeASCII()``
* ``PyUnicode_EncodeLatin1()``
* ``PyUnicode_EncodeUTF7()``
* ``PyUnicode_EncodeUTF8()``
* ``PyUnicode_EncodeUTF16()``
* ``PyUnicode_EncodeUTF32()``
* ``PyUnicode_EncodeUnicodeEscape()``
* ``PyUnicode_EncodeRawUnicodeEscape()``
* ``PyUnicode_EncodeCharmap()``
* ``PyUnicode_TranslateCharmap()``
* ``PyUnicode_EncodeDecimal()``
* ``PyUnicode_TransformDecimalToASCII()``
.. note::
`PEP 623 <https://www.python.org/dev/peps/pep-0623/>`_ propose to remove
Unicode object APIs relating to ``Py_UNICODE``. On the other hand, this PEP
is not relating to Unicode object. These PEPs are split because they have
different motivation and need different discussion.
Motivation
==========
In general, reducing the number of APIs that have been deprecated for
a long time and have few users is a good idea for not only it
improves the maintainability of CPython, but it also helps API users
and other Python implementations.
Rationale
=========
Deprecated since Python 3.3
---------------------------
``Py_UNICODE`` and APIs using it are deprecated since Python 3.3.
Inefficient
-----------
All of these APIs are implemented using ``PyUnicode_FromWideChar``.
So these APIs are inefficient when user want to encode Unicode
object.
Not used widely
---------------
When searching from top 4000 PyPI packages [1]_, only pyodbc use
these APIs.
* ``PyUnicode_EncodeUTF8()``
* ``PyUnicode_EncodeUTF16()``
pyodbc uses these APIs to encode Unicode object into bytes object.
So it is easy to fix it. [2]_
Alternative APIs
================
There are alternative APIs to accept ``PyObject *unicode`` instead of
``Py_UNICODE *``. Users can migrate to them.
=========================================
==========================================
Deprecated API Alternative APIs
=========================================
==========================================
``PyUnicode_Encode()`` ``PyUnicode_AsEncodedString()``
``PyUnicode_EncodeASCII()`` ``PyUnicode_AsASCIIString()`` \(1)
``PyUnicode_EncodeLatin1()`` ``PyUnicode_AsLatin1String()`` \(1)
``PyUnicode_EncodeUTF7()`` \(2)
``PyUnicode_EncodeUTF8()`` ``PyUnicode_AsUTF8String()`` \(1)
``PyUnicode_EncodeUTF16()`` ``PyUnicode_AsUTF16String()`` \(3)
``PyUnicode_EncodeUTF32()`` ``PyUnicode_AsUTF32String()`` \(3)
``PyUnicode_EncodeUnicodeEscape()`` ``PyUnicode_AsUnicodeEscapeString()``
``PyUnicode_EncodeRawUnicodeEscape()``
``PyUnicode_AsRawUnicodeEscapeString()``
``PyUnicode_EncodeCharmap()`` ``PyUnicode_AsCharmapString()`` \(1)
``PyUnicode_TranslateCharmap()`` ``PyUnicode_Translate()``
``PyUnicode_EncodeDecimal()`` \(4)
``PyUnicode_TransformDecimalToASCII()`` \(4)
=========================================
==========================================
Notes:
(1)
``const char *errors`` parameter is missing.
(2)
There is no public alternative API. But user can use generic
``PyUnicode_AsEncodedString()`` instead.
(3)
``const char *errors, int byteorder`` parameters are missing.
(4)
There is no direct replacement. But ``Py_UNICODE_TODECIMAL``
can be used instead. CPython uses
``_PyUnicode_TransformDecimalAndSpaceToASCII`` for converting
from Unicode to numbers instead.
Plan
====
Python 3.9
----------
Add ``Py_DEPRECATED(3.3)`` to following APIs. This change is committed
already [3]_. All other APIs have been marked ``Py_DEPRECATED(3.3)``
already.
* ``PyUnicode_EncodeDecimal()``
* ``PyUnicode_TransformDecimalToASCII()``.
Document all APIs as "will be removed in version 3.11".
Python 3.11
-----------
These APIs are removed.
* ``PyUnicode_Encode()``
* ``PyUnicode_EncodeASCII()``
* ``PyUnicode_EncodeLatin1()``
* ``PyUnicode_EncodeUTF7()``
* ``PyUnicode_EncodeUTF8()``
* ``PyUnicode_EncodeUTF16()``
* ``PyUnicode_EncodeUTF32()``
* ``PyUnicode_EncodeUnicodeEscape()``
* ``PyUnicode_EncodeRawUnicodeEscape()``
* ``PyUnicode_EncodeCharmap()``
* ``PyUnicode_TranslateCharmap()``
* ``PyUnicode_EncodeDecimal()``
* ``PyUnicode_TransformDecimalToASCII()``
Alternative ideas
=================
Instead of just removing deprecated APIs, we may be able to use thier
names with different signature.
Make some private APIs public
------------------------------
``PyUnicode_EncodeUTF7()`` doesn't have public alternative APIs.
Some APIs have alternative public APIs. But they are missing
``const char *errors`` or ``int byteorder`` parameters.
We can rename some private APIs and make them public to cover missing
APIs and parameters.
============================= ================================
Rename to Rename from
============================= ================================
``PyUnicode_EncodeASCII()`` ``_PyUnicode_AsASCIIString()``
``PyUnicode_EncodeLatin1()`` ``_PyUnicode_AsLatin1String()``
``PyUnicode_EncodeUTF7()`` ``_PyUnicode_EncodeUTF7()``
``PyUnicode_EncodeUTF8()`` ``_PyUnicode_AsUTF8String()``
``PyUnicode_EncodeUTF16()`` ``_PyUnicode_EncodeUTF16()``
``PyUnicode_EncodeUTF32()`` ``_PyUnicode_EncodeUTF32()``
============================= ================================
Pros:
* We have more consistent API set.
Cons:
* We have more public APIs to maintain.
* Existing public APIs are enough for most use cases, and
``PyUnicode_AsEncodedString()`` can be used in other cases.
Replace ``Py_UNICODE*`` with ``Py_UCS4*``
-----------------------------------------
We can replace ``Py_UNICODE`` (typedef of ``wchar_t``) with
``Py_UCS4``. Since builtin codecs support UCS-4, we don't need to
convert ``Py_UCS4*`` string to Unicode object.
Pros:
* We have more consistent API set.
* User can encode UCS-4 string in C without creating Unicode object.
Cons:
* We have more public APIs to maintain.
* Applications which uses UTF-8 or UTF-32 can not use these APIs
anyway.
* Other Python implementations may not have builtin codec for UCS-4.
* If we change the Unicode internal representation to UTF-8, we need
to keep UCS-4 support only for these APIs.
Replace ``Py_UNICODE*`` with ``wchar_t*``
-----------------------------------------
We can replace ``Py_UNICODE`` to ``wchar_t``.
Pros:
* We have more consistent API set.
* Backward compatible.
Cons:
* We have more public APIs to maintain.
* They are inefficient on platforms ``wchar_t*`` is UTF-16. It is
because built-in codecs supports only UCS-1, UCS-2, and UCS-4
input.
Rejected ideas
==============
Using runtime warning
---------------------
These APIs doesn't release GIL for now. Emitting a warning from
such APIs is not safe. See this example.
.. code-block::
PyObject *u = PyList_GET_ITEM(list, i); // u is borrowed reference.
PyObject *b = PyUnicode_EncodeUTF8(PyUnicode_AS_UNICODE(u),
PyUnicode_GET_SIZE(u), NULL);
// Assumes u is still living reference.
PyObject *t = PyTuple_Pack(2, u, b);
Py_DECREF(b);
return t;
If we emit Python warning from ``PyUnicode_EncodeUTF8()``, warning
filters and other threads may change the ``list`` and ``u`` can be
a dangling reference after ``PyUnicode_EncodeUTF8()`` returned.
Additionally, since we are not changing behavior but removing C APIs,
runtime ``DeprecationWarning`` might not helpful for Python
developers. We should warn to extension developers instead.
Discussions
===========
* `Plan to remove Py_UNICODE APis except PEP 623
<https://mail.python.org/archives/list/[email protected]/thread/S7KW2U6I…>`_
* `bpo-41123: Remove Py_UNICODE APIs except PEP 623:
<https://bugs.python.org/issue41123>`_
References
==========
.. [1] Source package list chosen from top 4000 PyPI packages.
(https://github.com/methane/notes/blob/master/2020/wchar-cache/package_list.…)
.. [2] pyodbc -- Don't use PyUnicode_Encode API #792
(https://github.com/mkleehammer/pyodbc/pull/792)
.. [3] Uncomment Py_DEPRECATED for Py_UNICODE APIs (GH-21318)
(https://github.com/python/cpython/commit/9c3840870814493fed62e140cfa43c2883…)
Copyright
=========
This document has been placed in the public domain.
--
Inada Naoki <songofacandy(a)gmail.com>
Hi,
Pathlib's symlink_to() and link_to() methods have different argument
orders, so:
a.symlink_to(b) # Creates a symlink from A to B
a.link_to(b) # Creates a hard link from B to A
I don't think link_to() was intended to be implemented this way, as the
docs say "Create a hard link pointing to a path named target.". It's also
inconsistent with everything else in pathlib, most obviously symlink_to().
Bug report here: https://bugs.python.org/issue39291
This /really/ irks me. Apparently it's too late to fix link_to(), so I'd
like to suggest we add a new hardlink_to() method that matches the
symlink_to() argument order. link_to() then becomes deprecated/undocumented.
Any thoughts?
Barney
Python Documentation, Python language improvement, and productive discussion
by Carol Willing Oct. 9, 2020 Oct. 9, 2020
Hi folks,
Earlier this year at the Python Language Summit, Ned Batchelder and I presented the concept of a Documentation Workgroup and a vision for the next few years:
- Slidedeck https://speakerdeck.com/willingc/cpython-documentation-the-next-5-years
- Blog post https://pyfound.blogspot.com/2020/04/cpython-documentation-next-5-years.html
Due to some health issues that I have had the past few months, I haven't yet set up the workgroup. It's a priority of mine for July. We will have an open call for workgroup participants.
There's a lot going on in the world with COVID19 that is impacting our lives directly and indirectly. I encourage the core development community to consider how what they share about their feelings on PEP8 may impact others. Clearly, this is an issue where it's unlikely that there will be universal agreement. As you consider additional posts about PEP8, I encourage you to think about whether your post improves the Python language before hitting Send.
Stay safe as we all live together in a world facing unusual constraints due to COVID19.
Warmly,
Carol
Hi,
I am writing to you on behalf of PyCon Estonia <https://pycon.ee> to invite
you to take part in the call for papers for our 2020 edition and join us as
a speaker at PyCon: https://pyconestonia.typeform.com/to/e0jriV
This is the third PyCon Estonia event after successful delivery in 2018 and
2019. PyCon Estonia is organised by our NGO Python Estonia
<https://pythonestonia.ee> which is dedicated to education and awareness
about Python in the region.
In previous years <https://www.youtube.com/watch?v=nMbbBQ4F0sc>, keynote
speakers at PyCon Estonia have included Travis Oliphant (Creator of NumPy)
and Kristo Vaher (Govt. CTO of Estonia). We've had around 300
participants join us for a live conference in Tallinn, Estonia with 7-9
excellent speakers from all walks of life talking about Python. This year
we already have Miguel Grinberg <https://blog.miguelgrinberg.com> as one of
our speakers.
Due to coronavirus, this PyCon will be an entirely virtual conference,
possibly with a bigger and more international audience. The theme for
PyCon Estonia
2020 is "The power of Python" and we want to talk about the real life
applications of Python and how digital products built on Python are
impacting the tech sector or the world in general.
We would really like to have you offer a possible topic for a talk at
PyCon. We intend to have a total of 8 talks of 30-minutes followed by a
10-minute Q&A. If this would be something you are interested in, please
submit a proposal here: https://pyconestonia.typeform.com/to/e0jriV before
the *15th August, 2020*.
I am happy to add that we are a diverse group organising PyCon Estonia
2020, and we are trying to make the conference as diverse as possible.
If you have any questions, please don't hesitate to write to me.
Best Regards,
*Amna Ahsan*
Chief Marketing Officer
*Python Estonia*
+372 5784 0436
Hey all,
We just recently finished working on the signup form for the upcoming 2020
Python Core Dev Sprint on Oct. 19th - 23rd. In addition to getting an
general idea of (virtual) attendance, this is being used to assess the
topics covered, optimal start/end times for each day, and preferred social
activities.
Anyone who is a CPython core developer, engaged in a core dev mentorship,
or a member of the Python triage team is welcome to attend!
Sign up to attend here: https://forms.gle/84NkyYt5g616fs1r5
We will be accepting late sign ups for this event since capacity is not a
significant limitation, but for the purposes of scheduling the best
possible times for everyone, it is requested that participants do so at
their earliest convenience.
Regards,
Kyle Stanley
Today I’m happy (and a little trepidatious) to announce the next
version of PEP 622, Pattern Matching. As authors we welcome Daniel F
Moisset in our midst. Daniel wrote a lot of the new text in this
version, which introduces the subject matter much more gently than the
first version did. He also convinced us to drop the `__match__`
protocol for now: the proposal stands quite well without that kind of
extensibility, and postponing it will allow us to design it at a later
time when we have more experience with how `match` is being used.
That said, the new version does not differ dramatically in what we
propose. Apart from dropping `__match__` we’re dropping the leading
dot to mark named constants, without a replacement, and everything
else looks like we’re digging in our heels. Why is that? Given the
firestorm of feedback we received and the numerous proposals (still
coming) for alternative syntax, it seems a bad tactic not to give up
something more substantial in order to get this proposal passed. Let
me explain.
Language design is not like politics. It’s not like mathematics
either, but I don’t think this situation is at all similar to
negotiating a higher minimum wage in exchange for a lower pension,
where you can definitely argue about exactly how much lower/higher
you’re willing to go. So I don’t think it’s right to propose making
the feature a little bit uglier just to get it accepted.
Frankly, 90% of the issue is about what among the authors we’ve dubbed
the “load/store” problem (although Tobias never tires to explain that
the “load” part is really “load-and-compare”). There’s a considerable
section devoted to this topic in the PEP, but I’d like to give it
another try here.
In case you’ve been avoiding python-dev lately, the problem is
this. Pattern matching lets you capture values from the subject,
similar to sequence unpacking, so that you can write for example
```
x = range(4)
match x:
case (a, b, *rest):
print(f"first={a}, second={b}, rest={rest}") # 0, 1, [2, 3]
```
Here the `case` line captures the contents of the subject `x` in three
variables named `a`, `b` and `rest`. This is easy to understand by
pretending that a pattern (i.e., what follows `case`) is like the LHS
of an assignment.
However, in order to make pattern matching more useful and versatile,
the pattern matching syntax also allows using literals instead of
capture variables. This is really handy when you want to distinguish
different cases based on some value, for example
```
match t:
case ("rect", real, imag):
return complex(real, imag)
case ("polar", r, phi):
return complex(r * cos(phi), r * sin(phi))
```
You might not even notice anything funny here if I didn’t point out
that `"rect"` and `"polar"` are literals -- it’s really quite
natural for patterns to support this once you think about it.
The problem that everybody’s been concerned about is that Python
programmers, like C programmers before them, aren’t too keen to have
literals like this all over their code, and would rather give names to
the literals, for example
```
USE_POLAR = "polar"
USE_RECT = "rect"
```
Now we would like to be able to replace those literals with the
corresponding names throughout our code and have everything work like
before:
```
match t:
case (USE_RECT, real, imag):
return complex(real, imag)
case (USE_POLAR, r, phi):
return complex(r * cos(phi), r * sin(phi))
```
Alas, the compiler doesn’t know that we want `USE_RECT` to be a
constant value to be matched while we intend `real` and `imag` to be
variables to be given the corresponding values captured from the
subject. So various clever ways have been proposed to distinguish the
two cases.
This discussion is not new to the authors: before we ever published
the first version of the PEP we vigorously debated this (it is Issue 1
in our tracker!), and other languages before us have also had to come
to grips with it. Even many statically compiled languages! The reason
is that for reasons of usability it’s usually deemed important that
their equivalent of `case` auto-declare the captured variables, and
variable declarations may hide (override) like-named variables in
outer scopes.
Scala, for example, uses several different rules: first, capture
variable names must start with a lowercase letter (so it would
handle the above example as intended); next, capture variables
cannot be dotted names (like `mod.var`); finally, you can enclose any
variable in backticks to force the compiler to see it as a load
instead of a store. Elixir uses another form of markup for loads: `x`
is a capture variable, but `^x` loads and compares the value of `x`.
There are a number of dead ends when looking for a solution that works
for Python. Checking at runtime whether a name is defined or not is
one of these: there are numerous reasons why this could be confusing,
not the least of which being that the `match` may be executed in a
loop and the variable may already be bound by a previous
iteration. (True, this has to do with the scope we’ve adopted for
capture variables. But believe me, giving each case clause its own
scope is quite horrible by itself, and there are other
action-at-a-distance effects that are equally bad.)
It’s been proposed to explicitly state the names of the variables
bound in a header of the `match` statement; but this doesn’t scale
when the number of cases becomes larger, and requires users to do
bookkeeping the compiler should be able to do. We’re really looking
for a solution that tells you when you’re looking at an individual
`case` which variables are captured and which are used for
load-and-compare.
Marking up the capture variables with some sigil (e.g. `$x` or `x?`)
or other markup (e.g. backticks or `<x>`) makes this common case ugly
and inconsistent: it’s unpleasant to see for example
```
case %x, %y:
print(x, y)
```
No other language we’ve surveyed uses special markup for capture
variables; some use special markup for load-and-compare, so we’ve
explored this. In fact, in version 1 of the PEP our long-debated
solution was to use a leading dot. This was however boohed off the
field, so for version 2 we reconsidered. In the end nothing struck our
fancy (if `.x` is unacceptable, it’s unclear why `^x` would be any
better), and we chose a simpler rule: named constants are only
recognized when referenced via some namespace, such as `mod.var` or
`Color.RED`.
We believe it’s acceptable that things looking like `mod.var` are
never considered capture variables -- the common use cases for `match`
are such that one would almost never want to capture into a different
namespace. (Just like you very rarely see `for self.i in …` and never
`except E as scope.var` -- the latter is illegal syntax and sets a
precedent.)
One author would dearly have seen Scala’s uppercase rule adopted, but
in the end was convinced by the others that this was a bad idea, both
because there’s no precedent in Python’s syntax, and because many
human languages simply don’t make the distinction between lowercase
and uppercase in their writing systems.
So what should you do if you have a local variable (say, a function
argument) that you want to use as a value in a pattern? One solution
is to capture the value in another variable and use a guard to compare
that variable to the argument:
```
def foo(x, spam):
match x:
case Point(p, q, context=c) if c == spam:
# Match
```
If this really is a deal-breaker after all other issues have been
settled, we could go back to considering some special markup for
load-and-compare of simple names (even though we expect this case to
be very rare). But there’s no pressing need to decide to do this now
-- we can always add new markup for this purpose in a future version,
as long as we continue to support dotted names without markup,
since that *is* a commonly needed case.
There’s one other issue where in the end we could be convinced to
compromise: whether to add an `else` clause in addition to `case
_`. In fact, we probably would already have added it, except for one
detail: it’s unclear whether the `else` should be aligned with `case`
or `match`. If we are to add this we would have to ask the Steering
Council to decide for us, as the authors deadlocked on this question.
Regarding the syntax for wildcards and OR patterns, the PEP explains
why `_` and `|` are the best choices here: no other language surveyed
uses anything but `_` for wildcards, and the vast majority uses `|`
for OR patterns. A similar argument applies to class patterns.
If you've made it so far, here are the links to check out, with an
open mind. As a reminder, the introductory sections (Abstract,
Overview, and Rationale and Goals) have been entirely rewritten and
also serve as introduction and tutorial.
- PEP 622: https://www.python.org/dev/peps/pep-0622/
- Playground:
https://mybinder.org/v2/gh/gvanrossum/patma/master?urlpath=lab/tree/playgro…
--
--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-…>
|
| You are visitor 01402503 — GeezerVison does not store the pages you look up. Best viewed with Netscape Navigator 4.7 or Internet Explorer 6 at 800×600. No cookies required. |
