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:
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/
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
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:
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)
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/
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
---------
