Mailman 3 February 2015 - Python-Dev

PEP 448 review
by Guido van Rossum 29 Mar '23

29 Mar '23

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)

7 17

PEP 1, PEP Purpose and Guidelines
by barry＠zope.com 18 May '21

18 May '21

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:

8 14

Surely "nullable" is a reasonable name?
by Larry Hastings 25 Apr '15

25 Apr '15

Argument Clinic "converters" specify how to convert an individual argument to the function you're defining. Although a converter could theoretically represent any sort of conversion, most of the time they directly represent types like "int" or "double" or "str". Because there's such variety in argument parsing, the converters are customizable with parameters. Many of these are common enough that Argument Clinic suggests some standard names. Examples: "zeroes=True" for strings and buffers means "permit internal \0 characters", and "bitwise=True" for unsigned integers means "copy the bits over, even if there's overflow/underflow, and even if the original is negative". A third example is "nullable=True", which means "also accept None for this parameter". This was originally intended for use with strings (compare the "s" and "z" format units for PyArg_ParseTuple), however it looks like we'll have a use for "nullable ints" in the ongoing Argument Clinic conversion work. Several people have said they found the name "nullable" surprising, suggesting I use another name like "allow_none" or "noneable". I, in turn, find their surprise surprising; "nullable" is a term long associated with exactly this concept. It's used in C# and SQL, and the term even has its own Wikipedia page: http://en.wikipedia.org/wiki/Nullable_type Most amusingly, Vala *used* to have an annotation called "(allow-none)", but they've broken it out into two annotations, "(nullable)" and "(optional)". http://blogs.gnome.org/desrt/2014/05/27/allow-none-is-dead-long-live-nullab… Before you say "the term 'nullable' will confuse end users", let me remind you: this is not user-facing. This is a parameter for an Argument Clinic converter, and will only ever be seen by CPython core developers. A group which I hope is not so easily confused. It's my contention that "nullable" is the correct name. But I've been asked to bring up the topic for discussion, to see if a consensus forms around this or around some other name. Let the bike-shedding begin, //arry/

13 29

libffi embedded in CPython
by Maciej Fijalkowski 25 Mar '15

25 Mar '15

After reading this http://bugs.python.org/issue23085 and remembering struggling having our own patches into cpython's libffi (but not into libffi itself), I wonder, is there any reason any more for libffi being included in CPython? Cheers, fijal

18 57

Re: [Python-Dev] Request for Pronouncement: PEP 441 - Improving Python ZIP Application Support
by Paul Moore 15 Mar '15

15 Mar '15

On 24 February 2015 at 18:24, Guido van Rossum <guido(a)python.org> wrote: > Here's my review. I really like where this is going but I have a few > questions and suggestions (I can't help myself :-). OK, I've updated both the PEP and the patch based on follow-up discussions. I think (again!) it is ready to go. I've included the updated PEP inline below, it'll be available at peps.python.org as soon as someone has a chance to upload it. Thanks to everyone for the various comments. If I've missed anything that someone thinks I'd said I would change, please let me know. Paul PEP: 441 Title: Improving Python ZIP Application Support Version: $Revision$ Last-Modified: $Date$ Author: Daniel Holth <dholth(a)gmail.com>, Paul Moore <p.f.moore(a)gmail.com> Discussions-To: https://mail.python.org/pipermail/python-dev/2015-February/138277.html Status: Draft Type: Standards Track Content-Type: text/x-rst Created: 30 March 2013 Post-History: 30 March 2013, 1 April 2013, 16 February 2015 Improving Python ZIP Application Support ======================================== Python has had the ability to execute directories or ZIP-format archives as scripts since version 2.6 [1]_. When invoked with a zip file or directory as its first argument the interpreter adds that directory to sys.path and executes the ``__main__`` module. These archives provide a great way to publish software that needs to be distributed as a single file script but is complex enough to need to be written as a collection of modules. This feature is not as popular as it should be mainly because it was not promoted as part of Python 2.6 [2]_, so that it is relatively unknown, but also because the Windows installer does not register a file extension (other than ``.py``) for this format of file, to associate with the launcher. This PEP proposes to fix these problems by re-publicising the feature, defining the ``.pyz`` and ``.pyzw`` extensions as "Python ZIP Applications" and "Windowed Python ZIP Applications", and providing some simple tooling to manage the format. A New Python ZIP Application Extension ====================================== The terminology "Python Zip Application" will be the formal term used for a zip-format archive that contains Python code in a form that can be directly executed by Python (specifically, it must have a ``__main__.py`` file in the root directory of the archive). The extension ``.pyz`` will be formally associated with such files. The Python 3.5 installer will associate ``.pyz`` and ``.pyzw`` "Python Zip Applications" with the platform launcher so they can be executed. A ``.pyz`` archive is a console application and a ``.pyzw`` archive is a windowed application, indicating whether the console should appear when running the app. On Unix, it would be ideal if the ``.pyz`` extension and the name "Python Zip Application" were registered (in the mime types database?). However, such an association is out of scope for this PEP. Python Zip applications can be prefixed with a ``#!`` line pointing to the correct Python interpreter and an optional explanation:: #!/usr/bin/env python3 # Python application packed with zipapp module (binary contents of archive) On Unix, this allows the OS to run the file with the correct interpreter, via the standard "shebang" support. On Windows, the Python launcher implements shebang support. However, it is always possible to execute a ``.pyz`` application by supplying the filename to the Python interpreter directly. As background, ZIP archives are defined with a footer containing relative offsets from the end of the file. They remain valid when concatenated to the end of any other file. This feature is completely standard and is how self-extracting ZIP archives and the bdist_wininst installer format work. Minimal Tooling: The zipapp Module ================================== This PEP also proposes including a module for working with these archives. The module will contain functions for working with Python zip application archives, and a command line interface (via ``python -m zipapp``) for their creation and manipulation. More complete tools for managing Python Zip Applications are encouraged as 3rd party applications on PyPI. Currently, pyzzer [5]_ and pex [6]_ are two such tools. Module Interface ---------------- The zipapp module will provide the following functions: ``create_archive(source, target=None, interpreter=None, main=None)`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Create an application archive from *source*. The source can be any of the following: * The name of a directory, in which case a new application archive will be created from the content of that directory. * The name of an existing application archive file, in which case the file is copied to the target. The file name should include the ``.pyz`` extension, if required. * A file object open for reading in bytes mode. The content of the file should be an application archive, and the file object is assumed to be positioned at the start of the archive. The *target* argument determines where the resulting archive will be written: * If it is the name of a file, the archive will be written to that file. * If it is an open file object, the archive will be written to that file object, which must be open for writing in bytes mode. * If the target is omitted (or None), the source must be a directory and the target will be a file with the same name as the source, with a ``.pyz`` extension added. The *interpreter* argument specifies the name of the Python interpreter with which the archive will be executed. It is written as a "shebang" line at the start of the archive. On Unix, this will be interpreted by the OS, and on Windows it will be handled by the Python launcher. Omitting the *interpreter* results in no shebang line being written. If an interpreter is specified, and the target is a filename, the executable bit of the target file will be set. The *main* argument specifies the name of a callable which will be used as the main program for the archive. It can only be specified if the source is a directory, and the source does not already contain a ``__main__.py`` file. The *main* argument should take the form "pkg.module:callable" and the archive will be run by importing "pkg.module" and executing the given callable with no arguments. It is an error to omit *main* if the source is a directory and does not contain a ``__main__.py`` file, as otherwise the resulting archive would not be executable. If a file object is specified for *source* or *target*, it is the caller's responsibility to close it after calling create_archive. When copying an existing archive, file objects supplied only need ``read`` and ``readline``, or ``write`` methods. When creating an archive from a directory, if the target is a file object it will be passed to the ``zipfile.ZipFile`` class, and must supply the methods needed by that class. ``get_interpreter(archive)`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Returns the interpreter specified in the shebang line of the *archive*. If there is no shebang, the function returns ``None``. The *archive* argument can be a filename or a file-like object open for reading in bytes mode. Command Line Usage ------------------ The zipapp module can be run with the python ``-m`` flag. The command line interface is as follows:: python -m zipapp directory [options] Create an archive from the given directory. An archive will be created from the contents of that directory. The archive will have the same name as the source directory with a .pyz extension. The following options can be specified: -o archive / --output archive The destination archive will have the specified name. The given name will be used as written, so should include the ".pyz" extension. -p interpreter / --python interpreter The given interpreter will be written to the shebang line of the archive. If this option is not given, the archive will have no shebang line. -m pkg.mod:fn / --main pkg.mod:fn The source directory must not have a __main__.py file. The archiver will write a __main__.py file into the target which calls fn from the module pkg.mod. The behaviour of the command line interface matches that of ``zipapp.create_archive()``. In addition, it is possible to use the command line interface to work with an existing archive:: python -m zipapp app.pyz --show Displays the shebang line of an archive. Output is of the form Interpreter: /usr/bin/env or Interpreter: <none> and is intended for diagnostic use, not for scripts. python -m zipapp app.pyz -o newapp.pyz [-p interpreter] Copy app.pyz to newapp.pyz, modifying the shebang line based on the -p option (as for creating an archive, no -p option means remove the shebang line). Specifying a destination is mandatory. In-place modification of an archive is *not* supported, as the risk of damaging archives is too great for a simple tool. As noted, the archives are standard zip files, and so can be unpacked using any standard ZIP utility or Python's zipfile module. For this reason, no interfaces to list the contents of an archive, or unpack them, are provided or needed. FAQ --- Are you sure a standard ZIP utility can handle ``#!`` at the beginning? Absolutely. The zipfile specification allows for arbitrary data to be prepended to a zipfile. This feature is commonly used by "self-extracting zip" programs. If your archive program can't handle this, it is a bug in your archive program. Isn't zipapp just a very thin wrapper over the zipfile module? Yes. If you prefer to build your own Python zip application archives using other tools, they will work just as well. The zipapp module is a convenience, nothing more. Why not use just use a ``.zip`` or ``.py`` extension? Users expect a ``.zip`` file to be opened with an archive tool, and expect a ``.py`` file to contain readable text. Both would be confusing for this use case. How does this compete with existing package formats? The sdist, bdist and wheel formats are designed for packaging of modules to be installed into an existing Python installation. They are not intended to be used without installing. The executable zip format is specifically designed for standalone use, without needing to be installed. They are in effect a multi-file version of a standalone Python script. Rejected Proposals ================== Convenience Values for Shebang Lines ------------------------------------ Is it worth having "convenience" forms for any of the common interpreter values? For example, ``-p 3`` meaning the same as ``-p "/usr/bin/env python3"``. It would save a lot of typing for the common cases, as well as giving cross-platform options for people who don't want or need to understand the intricacies of shebang handling on "other" platforms. Downsides are that it's not obvious how to translate the abbreviations. For example, should "3" mean "/usr/bin/env python3", "/usr/bin/python3", "python3", or something else? Also, there is no obvious short form for the key case of "/usr/bin/env python" (any available version of Python), which could easily result in scripts being written with overly-restrictive shebang lines. Overall, this seems like there are more problems than benefits, and as a result has been dropped from consideration. Registering ``.pyz`` as a Media Type ------------------------------------ It was suggested [3]_ that the ``.pyz`` extension should be registered in the Unix database of extensions. While it makes sense to do this as an equivalent of the Windows installer registering the extension, the ``.py`` extension is not listed in the media types database [4]_. It doesn't seem reasonable to register ``.pyz`` without ``.py``, so this idea has been omitted from this PEP. An interested party could arrange for *both* ``.py`` and ``.pyz`` to be registered at a future date. Default Interpreter ------------------- The initial draft of this PEP proposed using ``/usr/bin/env python`` as the default interpreter. Unix users have problems with this behaviour, as the default for the python command on many distributions is Python 2, and it is felt that this PEP should prefer Python 3 by default. However, using a command of ``python3`` can result in unexpected behaviour for Windows users, where the default behaviour of the launcher for the command ``python`` is commonly customised by users, but the behaviour of ``python3`` may not be modified to match. As a result, the principle "in the face of ambiguity, refuse to guess" has been invoked, and archives have no shebang line unless explicitly requested. On Windows, the archives will still be run (with the default Python) by the launcher, and on Unix, the archives can be run by explicitly invoking the desired Python interpreter. Command Line Tool to Manage Shebang Lines ----------------------------------------- It is conceivable that users would want to modify the shebang line for an existing archive, or even just display the current shebang line. This is tricky to do so with existing tools (zip programs typically ignore prepended data totally, and text editors can have trouble editing files containing binary data). The zipapp module provides functions to handle the shebang line, but does not include a command line interface to that functionality. This is because it is not clear how to provide one without the resulting interface being over-complex and potentially confusing. Changing the shebang line is expected to be an uncommon requirement. Reference Implementation ======================== A reference implementation is at http://bugs.python.org/issue23491. References ========== .. [1] Allow interpreter to execute a zip file (http://bugs.python.org/issue1739468) .. [2] Feature is not documented (http://bugs.python.org/issue17359) .. [3] Discussion of adding a .pyz mime type on python-dev (https://mail.python.org/pipermail/python-dev/2015-February/138338.html) .. [4] Register of media types (http://www.iana.org/assignments/media-types/media-types.xhtml) .. [5] pyzzer - A tool for creating Python-executable archives (https://pypi.python.org/pypi/pyzzer) .. [6] pex - The PEX packaging toolchain (https://pypi.python.org/pypi/pex) The discussion of this PEP took place on the python-dev mailing list, in the thread starting at https://mail.python.org/pipermail/python-dev/2015-February/138277.html Copyright ========= This document has been placed into the public domain. .. Local Variables: mode: indented-text indent-tabs-mode: nil sentence-end-double-space: t fill-column: 70 coding: utf-8 End:

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PEP 485 review (isclose())
by Guido van Rossum 05 Mar '15

05 Mar '15

I think it's time to accept PEP 485. I've re-read it once more, and it looks like the text is in great shape. (My only recommendation would be to update the Abstract to state that we're specifically adding math.isclose().) A wording question: "This implementation has a flag that lets the user select which relative tolerance test to apply -- this PEP does not suggest that that be retained, but rather than the weak test be selected." -- I think this was meant to say "... rather *that* the weak test be selected", right? (It would be nice if the sample implementation defaulted to the choice in the PEP.) However, those are just minor edits, and I hereby approve the PEP. Thanks Chris and everyone else for the fruitful discussion (and thanks especially to Chris for eventually ending the bikeshedding and writing a PEP that explains each of the choices). Congrats! -- --Guido van Rossum (python.org/~guido)

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Any volunteers to implement PEP 479?
by Guido van Rossum 04 Mar '15

04 Mar '15

There's a proof of concept patch in http://bugs.python.org/issue22906, but it doesn't have the __future__ import and probably gets other details wrong. Reference: PEP 479 -- Change StopIteration handling inside generators <https://www.python.org/dev/peps/pep-0479/> -- --Guido van Rossum (python.org/~guido)

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[RELEASED] Python 3.4.3 is now available
by Larry Hastings 27 Feb '15

27 Feb '15

On behalf of the Python development community and the Python 3.4 release team, I'm pleased to announce the availability of Python 3.4.3. Python 3.4.3 has many bugfixes and other small improvements over 3.4.2. You can find it here: https://www.python.org/downloads/release/python-343/ The release slipped by two or three days, depending on what time zone you're in. This is my fault--I apologize for the inconvenience. Cheers, //arry/

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Summary of Python tracker Issues
by Python tracker 27 Feb '15

27 Feb '15

ACTIVITY SUMMARY (2015-02-20 - 2015-02-27) Python tracker at http://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 4788 (+18) closed 30510 (+26) total 35298 (+44) Open issues with patches: 2245 Issues opened (34) ================== #23458: [2.7] random: make the file descriptor non-inheritable (on POS http://bugs.python.org/issue23458 reopened by haypo #23494: adding timedelta to datetime object is not timezone aware http://bugs.python.org/issue23494 opened by gilsho #23495: The writer.writerows method should be documented as accepting http://bugs.python.org/issue23495 opened by Steven.Barker #23496: Steps for Android Native Build of Python 3.4.2 http://bugs.python.org/issue23496 opened by chaselton #23498: Expose http.cookiejar.split_header_words() http://bugs.python.org/issue23498 opened by vadmium #23500: Argument Clinic: multiple macro definition http://bugs.python.org/issue23500 opened by serhiy.storchaka #23501: Argument Clinic: generate code into separate files by default http://bugs.python.org/issue23501 opened by serhiy.storchaka #23502: pprint: added support for mapping proxy http://bugs.python.org/issue23502 opened by serhiy.storchaka #23503: undefined behavior in Objects/obmalloc.c http://bugs.python.org/issue23503 opened by dwight.guth #23504: Add __all__ into types http://bugs.python.org/issue23504 opened by serhiy.storchaka #23505: Urlparse insufficient validation leads to open redirect http://bugs.python.org/issue23505 opened by yaaboukir #23507: Tuple creation is too slow http://bugs.python.org/issue23507 opened by serhiy.storchaka #23508: Document & unittest the subprocess.getstatusoutput() status va http://bugs.python.org/issue23508 opened by gregory.p.smith #23509: Speed up Counter operators http://bugs.python.org/issue23509 opened by joern #23510: multiprocessing bug SyncManager and 'with' http://bugs.python.org/issue23510 opened by Cezary.Wagner #23512: List of builtins is not alphabetical on https://docs.python.or http://bugs.python.org/issue23512 opened by edsouza #23513: Add support for classes/object model in multiprocessing/pickle http://bugs.python.org/issue23513 opened by Cezary.Wagner #23514: multiprocessing documentation - little more examples for paral http://bugs.python.org/issue23514 opened by Cezary.Wagner #23516: pip: urllib3 does not encode userinfo section of URL with auth http://bugs.python.org/issue23516 opened by leotan #23517: datetime.utcfromtimestamp parses timestamps incorrectly http://bugs.python.org/issue23517 opened by tbarbugli #23520: test_os failed (python-3.4.3) http://bugs.python.org/issue23520 opened by avoevodkin #23521: OverflowError from timedelta * float in datetime.py http://bugs.python.org/issue23521 opened by belopolsky #23522: Misleading note in Statistics module documentation http://bugs.python.org/issue23522 opened by Journeyman08 #23524: Use _set_thread_local_invalid_parameter_handler in posixmodule http://bugs.python.org/issue23524 opened by steve.dower #23525: isbuiltin, isroutine, etc. http://bugs.python.org/issue23525 opened by abarnert #23526: Silence resource warnings in test_httplib http://bugs.python.org/issue23526 opened by ashkop #23527: test_smtpnet uses incorrect port for STARTTLS http://bugs.python.org/issue23527 opened by ashkop #23528: Limit decompressed data when reading from GzipFile http://bugs.python.org/issue23528 opened by vadmium #23529: Limit decompressed data when reading from LZMAFile and BZ2File http://bugs.python.org/issue23529 opened by vadmium #23530: os and multiprocessing.cpu_count do not respect cpuset/affinit http://bugs.python.org/issue23530 opened by jtaylor #23531: SSL operations cause entire process to hang http://bugs.python.org/issue23531 opened by johnkw #23532: add example of 'first match wins' to regex "|" documentation? http://bugs.python.org/issue23532 opened by Rick Otten #23534: `test_longdouble` fails on Mac when using system libffi (versi http://bugs.python.org/issue23534 opened by Maxime Belanger #23536: Add explicit information on config file format not supporting http://bugs.python.org/issue23536 opened by piotr.dobrogost Most recent 15 issues with no replies (15) ========================================== #23536: Add explicit information on config file format not supporting http://bugs.python.org/issue23536 #23527: test_smtpnet uses incorrect port for STARTTLS http://bugs.python.org/issue23527 #23525: isbuiltin, isroutine, etc. http://bugs.python.org/issue23525 #23522: Misleading note in Statistics module documentation http://bugs.python.org/issue23522 #23520: test_os failed (python-3.4.3) http://bugs.python.org/issue23520 #23512: List of builtins is not alphabetical on https://docs.python.or http://bugs.python.org/issue23512 #23504: Add __all__ into types http://bugs.python.org/issue23504 #23503: undefined behavior in Objects/obmalloc.c http://bugs.python.org/issue23503 #23502: pprint: added support for mapping proxy http://bugs.python.org/issue23502 #23501: Argument Clinic: generate code into separate files by default http://bugs.python.org/issue23501 #23498: Expose http.cookiejar.split_header_words() http://bugs.python.org/issue23498 #23487: argparse: add_subparsers 'action' broken http://bugs.python.org/issue23487 #23485: PEP 475: handle EINTR in the select and selectors module http://bugs.python.org/issue23485 #23470: OpenBSD buildbot uses wrong stdlib http://bugs.python.org/issue23470 #23469: Delete Misc/*.wpr files http://bugs.python.org/issue23469 Most recent 15 issues waiting for review (15) ============================================= #23529: Limit decompressed data when reading from LZMAFile and BZ2File http://bugs.python.org/issue23529 #23528: Limit decompressed data when reading from GzipFile http://bugs.python.org/issue23528 #23527: test_smtpnet uses incorrect port for STARTTLS http://bugs.python.org/issue23527 #23526: Silence resource warnings in test_httplib http://bugs.python.org/issue23526 #23524: Use _set_thread_local_invalid_parameter_handler in posixmodule http://bugs.python.org/issue23524 #23521: OverflowError from timedelta * float in datetime.py http://bugs.python.org/issue23521 #23509: Speed up Counter operators http://bugs.python.org/issue23509 #23507: Tuple creation is too slow http://bugs.python.org/issue23507 #23504: Add __all__ into types http://bugs.python.org/issue23504 #23502: pprint: added support for mapping proxy http://bugs.python.org/issue23502 #23501: Argument Clinic: generate code into separate files by default http://bugs.python.org/issue23501 #23496: Steps for Android Native Build of Python 3.4.2 http://bugs.python.org/issue23496 #23492: Argument Clinic: improve generated parser for 1-argument funct http://bugs.python.org/issue23492 #23491: PEP 441 - Improving Python Zip Application Support http://bugs.python.org/issue23491 #23488: Random objects twice as big as necessary on 64-bit builds http://bugs.python.org/issue23488 Top 10 most discussed issues (10) ================================= #23491: PEP 441 - Improving Python Zip Application Support http://bugs.python.org/issue23491 26 msgs #23496: Steps for Android Native Build of Python 3.4.2 http://bugs.python.org/issue23496 24 msgs #23521: OverflowError from timedelta * float in datetime.py http://bugs.python.org/issue23521 17 msgs #23524: Use _set_thread_local_invalid_parameter_handler in posixmodule http://bugs.python.org/issue23524 14 msgs #23493: optimize sort_keys in json module by using operator.itemgetter http://bugs.python.org/issue23493 12 msgs #23517: datetime.utcfromtimestamp parses timestamps incorrectly http://bugs.python.org/issue23517 12 msgs #23492: Argument Clinic: improve generated parser for 1-argument funct http://bugs.python.org/issue23492 8 msgs #20323: Argument Clinic: docstring_prototype output causes build failu http://bugs.python.org/issue20323 7 msgs #23314: Disabling CRT asserts in debug build http://bugs.python.org/issue23314 7 msgs #23458: [2.7] random: make the file descriptor non-inheritable (on POS http://bugs.python.org/issue23458 7 msgs Issues closed (25) ================== #5700: io.FileIO calls flush() after file closed http://bugs.python.org/issue5700 closed by serhiy.storchaka #6639: turtle: _tkinter.TclError: invalid command name ".10170160" http://bugs.python.org/issue6639 closed by serhiy.storchaka #15955: bz2, lzma: add option to limit output size http://bugs.python.org/issue15955 closed by pitrou #20780: Shadowed (duplicate name but different body) test in test_stat http://bugs.python.org/issue20780 closed by benjamin.peterson #21934: OpenBSD has no /dev/full device http://bugs.python.org/issue21934 closed by serhiy.storchaka #22113: memoryview and struct.pack_into http://bugs.python.org/issue22113 closed by serhiy.storchaka #22435: socketserver.TCPSocket leaks socket to garbage collector if se http://bugs.python.org/issue22435 closed by berker.peksag #23152: fstat64 required on Windows http://bugs.python.org/issue23152 closed by steve.dower #23215: MemoryError with custom error handlers and multibyte codecs http://bugs.python.org/issue23215 closed by serhiy.storchaka #23245: urllib2: urlopen() gets exception(kwargs bug?) http://bugs.python.org/issue23245 closed by Douman #23374: pydoc 3.x raises UnicodeEncodeError on sqlite3 package http://bugs.python.org/issue23374 closed by serhiy.storchaka #23476: SSL cert verify fail for "www.verisign.com" http://bugs.python.org/issue23476 closed by pitrou #23489: atexit handlers are not executed when using multiprocessing.Po http://bugs.python.org/issue23489 closed by davin #23490: allocation (and overwrite) of a 0 byte buffer http://bugs.python.org/issue23490 closed by serhiy.storchaka #23497: textwrap.dedent doesn't work properly with embedded strings co http://bugs.python.org/issue23497 closed by ned.deily #23499: Minor grammar issue in mimetypes.rst http://bugs.python.org/issue23499 closed by ned.deily #23506: Data Structure of Dict not changing its value as expected http://bugs.python.org/issue23506 closed by zach.ware #23511: Broken code example in email module documentation http://bugs.python.org/issue23511 closed by berker.peksag #23515: Bad logic in timsort's merge_collapse http://bugs.python.org/issue23515 closed by python-dev #23518: Misplaced diagnostic caret for some SyntaxErrors http://bugs.python.org/issue23518 closed by zach.ware #23519: using asyncio.iscoroutinefunction() on a functools.partial obj http://bugs.python.org/issue23519 closed by gvanrossum #23523: cmath.atanh has wrong output http://bugs.python.org/issue23523 closed by benjamin.peterson #23533: MacOSX Python child process running urlopen crashed when tkMes http://bugs.python.org/issue23533 closed by ned.deily #23535: os.path.join() wrong concatenation of "C:" on Windows http://bugs.python.org/issue23535 closed by eric.smith #23537: BaseSubprocessTransport includes two unused methods http://bugs.python.org/issue23537 closed by haypo

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Update to PEP 11 to clarify garnering platform support
by Brett Cannon 27 Feb '15

27 Feb '15

Here is some proposed wording. Since it is more of a clarification of what it takes to garner support -- which is just a new section -- rather than a complete rewrite I'm including just the diff to make it easier to read the changes. *diff -r 49d18bb47ebc pep-0011.txt* *--- a/pep-0011.txt Wed May 14 11:18:22 2014 -0400* *+++ b/pep-0011.txt Fri May 16 13:48:30 2014 -0400* @@ -2,22 +2,21 @@ Title: Removing support for little used platforms Version: $Revision$ Last-Modified: $Date$ -Author: martin(a)v.loewis.de (Martin von Löwis) +Author: Martin von Löwis <martin(a)v.loewis.de>, + Brett Cannon <brett(a)python.org> Status: Active Type: Process Content-Type: text/x-rst Created: 07-Jul-2002 Post-History: 18-Aug-2007 + 16-May-2014 Abstract -------- -This PEP documents operating systems (platforms) which are not -supported in Python anymore. For some of these systems, -supporting code might be still part of Python, but will be removed -in a future release - unless somebody steps forward as a volunteer -to maintain this code. +This PEP documents how an operating system (platform) garners +support in Python as well as documenting past support. Rationale @@ -37,16 +36,53 @@ change to the Python source code will work on all supported platforms. -To reduce this risk, this PEP proposes a procedure to remove code -for platforms with no Python users. +To reduce this risk, this PEP specifies what is required for a +platform to be considered supported by Python as well as providing a +procedure to remove code for platforms with little or no Python +users. +Supporting platforms +-------------------- + +Gaining official platform support requires two things. First, a core +developer needs to volunteer to maintain platform-specific code. This +core developer can either already be a member of the Python +development team or be given contributor rights on the basis of +maintaining platform support (it is at the discretion of the Python +development team to decide if a person is ready to have such rights +even if it is just for supporting a specific platform). + +Second, a stable buildbot must be provided [2]_. This guarantees that +platform support will not be accidentally broken by a Python core +developer who does not have personal access to the platform. For a +buildbot to be considered stable it requires that the machine be +reliably up and functioning (but it is up to the Python core +developers to decide whether to promote a buildbot to being +considered stable). + +This policy does not disqualify supporting other platforms +indirectly. Patches which are not platform-specific but still done to +add platform support will be considered for inclusion. For example, +if platform-independent changes were necessary in the configure +script which was motivated to support a specific platform that would +be accepted. Patches which add platform-specific code such as the +name of a specific platform to the configure script will generally +not be accepted without the platform having official support. + +CPU architecture and compiler support are viewed in a similar manner +as platforms. For example, to consider the ARM architecture supported +a buildbot running on ARM would be required along with support from +the Python development team. In general it is not required to have +a CPU architecture run under every possible platform in order to be +considered supported. Unsupporting platforms ---------------------- -If a certain platform that currently has special code in it is -deemed to be without Python users, a note must be posted in this -PEP that this platform is no longer actively supported. This +If a certain platform that currently has special code in Python is +deemed to be without Python users or lacks proper support from the +Python development team and/or a buildbot, a note must be posted in +this PEP that this platform is no longer actively supported. This note must include: - the name of the system @@ -69,8 +105,8 @@ forward and offer maintenance. -Resupporting platforms ----------------------- +Re-supporting platforms +----------------------- If a user of a platform wants to see this platform supported again, he may volunteer to maintain the platform support. Such an @@ -101,7 +137,7 @@ release is made. Developers of extension modules will generally need to use the same Visual Studio release; they are concerned both with the availability of the versions they need to use, and with keeping -the zoo of versions small. The Python source tree will keep +the zoo of versions small. The Python source tree will keep unmaintained build files for older Visual Studio releases, for which patches will be accepted. Such build files will be removed from the source tree 3 years after the extended support for the compiler has @@ -223,6 +259,7 @@ ---------- .. [1] http://support.microsoft.com/lifecycle/ +.. [2] http://buildbot.python.org/3.x.stable/ Copyright ---------

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