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
-------------------- snip snip --------------------
Title: PEP Purpose and Guidelines
Version: $Revision: 1.36 $
Last-Modified: $Date: 2002/07/29 18:34:59 $
Author: Barry A. Warsaw, Jeremy Hylton
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
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
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 or feature request tracker.
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
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
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
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
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. 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
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.
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.
PEP 9 contains a boilerplate 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
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  for more details.
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  for more information about PEP style
 PEP 1, PEP Purpose and Guidelines, Warsaw, Hylton
If you decide to provide an explicit URL for a PEP, please use
this as the URL template:
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
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 or better yet, the SourceForge patch manager 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
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
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
References and Footnotes
 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
 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
 PEP 9, Sample PEP Template
This document has been placed in the public domain.
> The point isn't about my suffering as such. The point is more that
> python-dev owns a tiny amount of the code out there, and I don't believe we
> should put Python's users through this.
> Sure - I would be happy to "upgrade" all the win32all code, no problem. I
> am also happy to live in the bleeding edge and take some pain that will
> The issue is simply the user base, and giving Python a reputation of not
> being able to painlessly upgrade even dot revisions.
I agree with all this.
[As I imagined explicit syntax did not catch up and would require
lot of discussions.]
> > Another way is to use special rules
> > (similar to those for class defs), e.g. having
> > <frag>
> > y=3
> > def f():
> > exec "y=2"
> > def g():
> > return y
> > return g()
> > print f()
> > </frag>
> > # print 3.
> > Is that confusing for users? maybe they will more naturally expect 2
> > as outcome (given nested scopes).
> This seems the best compromise to me. It will lead to the least
> broken code, because this is the behavior that we had before nested
> scopes! It is also quite easy to implement given the current
> implementation, I believe.
> Maybe we could introduce a warning rather than an error for this
> situation though, because even if this behavior is clearly documented,
> it will still be confusing to some, so it is better if we outlaw it in
> some future version.
Yes this can be easy to implement but more confusing situations can arise:
What should this print? the situation leads not to a canonical solution
as class def scopes.
from foo import *
> > This probably won't be a very popular suggestion, but how about pulling
> > nested scopes (I assume they are at the root of the problem)
> > until this can be solved cleanly?
> Agreed. While I think nested scopes are kinda cool, I have lived without
> them, and really without missing them, for years. At the moment the cure
> appears worse then the symptoms in at least a few cases. If nothing else,
> it compromises the elegant simplicity of Python that drew me here in the
> first place!
> Assuming that people really _do_ want this feature, IMO the bar should be
> raised so there are _zero_ backward compatibility issues.
I don't say anything about pulling nested scopes (I don't think my opinion
can change things in this respect)
but I should insist that without explicit syntax IMO raising the bar
has a too high impl cost (both performance and complexity) or creates
> >Assuming that people really _do_ want this feature, IMO the bar should be
> >raised so there are _zero_ backward compatibility issues.
> Even at the cost of additional implementation complexity? At the cost
> of having to learn "scopes are nested, unless you do these two things
> in which case they're not"?
> Let's not waffle. If nested scopes are worth doing, they're worth
> breaking code. Either leave exec and from..import illegal, or back
> out nested scopes, or think of some better solution, but let's not
> introduce complicated backward compatibility hacks.
IMO breaking code would be ok if we issue warnings today and implement
nested scopes issuing errors tomorrow. But this is simply a statement
about principles and raised impression.
IMO import * in an inner scope should end up being an error,
not sure about 'exec's.
We will need a final BDFL statement.
regards, Samuele Pedroni.
Title: Support for System Upgrades
Version: $Revision: 0.0 $
Author: mal(a)lemburg.com (Marc-Andr? Lemburg)
Type: Standards Track
This PEP proposes strategies to allow the Python standard library
to be upgraded in parts without having to reinstall the complete
distribution or having to wait for a new patch level release.
Python currently does not allow overriding modules or packages in
the standard library per default. Even though this is possible by
defining a PYTHONPATH environment variable (the paths defined in
this variable are prepended to the Python standard library path),
there is no standard way of achieving this without changing the
Since Python's standard library is starting to host packages which
are also available separately, e.g. the distutils, email and PyXML
packages, which can also be installed independently of the Python
distribution, it is desireable to have an option to upgrade these
packages without having to wait for a new patch level release of
the Python interpreter to bring along the changes.
This PEP proposes two different but not necessarily conflicting
1. Adding a new standard search path to sys.path:
$stdlibpath/system-packages just before the $stdlibpath
entry. This complements the already existing entry for site
add-ons $stdlibpath/site-packages which is appended to the
sys.path at interpreter startup time.
To make use of this new standard location, distutils will need
to grow support for installing certain packages in
$stdlibpath/system-packages rather than the standard location
for third-party packages $stdlibpath/site-packages.
2. Tweaking distutils to install directly into $stdlibpath for the
system upgrades rather than into $stdlibpath/site-packages.
The first solution has a few advantages over the second:
* upgrades can be easily identified (just look in
* upgrades can be deinstalled without affecting the rest
of the interpreter installation
* modules can be virtually removed from packages; this is
due to the way Python imports packages: once it finds the
top-level package directory it stay in this directory for
all subsequent package submodule imports
* the approach has an overall much cleaner design than the
hackish install on top of an existing installation approach
The only advantages of the second approach are that the Python
interpreter does not have to changed and that it works with
older Python versions.
Both solutions require changes to distutils. These changes can
also be implemented by package authors, but it would be better to
define a standard way of switching on the proposed behaviour.
Solution 1: Python 2.3 and up
Solution 2: all Python versions supported by distutils
This document has been placed in the public domain.
CEO eGenix.com Software GmbH
eGenix.com -- Makers of the Python mx Extensions: mxDateTime,mxODBC,...
Python Consulting: http://www.egenix.com/
Python Software: http://www.egenix.com/files/python/
Now that I'm relieved by sharing with you my feelings, ;-)
what's the best path to get python-bz2 module into Python 2.3?
Do you think it's something which should be in the core, or it'd
be better to keep it as an external module?
The code is currently maintained at http://python-bz2.sf.net, if
someone wants to have a look at it.
[ 2AAC 7928 0FBF 0299 5EB5 60E2 2253 B29A 6664 3A0C ]
I recently came across an announcement about the the Strongtalk system,
which contains the first fully developed strong, static type system for
Smalltalk. I wondered whether there might be useful ideas there for those
looking into static typing for Python.
After a long time of inactivity, I hope to be back to some python
hacking. Before getting into any coding, I'd like to discuss with
you some conceptual and boring stuff I have in my mind.
In the past I have given small contributions to the python standard
distribution. Unfortunately (for myself), I slowed down until I stopped
contributing, even though I have a great affect by the interpreter. Now
I realize that one of the reasons I've stopped contributing is because
there's a large inertia in getting stuff reviewed. The reason why this
is happening seems more aparent now that I was off for a while: there's
a small core of very busy developers working on core/essential/hard
stuff *and* in code reviewing as well.
At the same time, I've seen Guido and others bothered a few times
because of the lack of man power. So the question is: how do I, a
developer which feels capable of helping in python's development, can
get some of the tasks which take your time out of your hands? Or even,
how is it possible to improve some part of the development process by
giving people like me some instructions? Also, isn't it easy to point
out what's wrong in a commit from someone who is following the
development process for a while than taking the time to review its code
in the sourceforge patch system?
My feeling is that the Python development is currently overly
centralized, and that you might be suffering from that now, by being
unable to handover some of your tasks to someone else. I feel that
everytime I send a patch, besides being contributing, I'm also
overloading you with more stuff to review and comment and etc. Perhaps
the fallback costs for some wrong commit is too high now (did I heard
someone mentioning subversion?)?!
Could someone please discuss that issues with me, and perhaps just kick
me away saying that I'm crazy? :-)
[ 2AAC 7928 0FBF 0299 5EB5 60E2 2253 B29A 6664 3A0C ]
Guido van Rossum <guido(a)python.org> writes:
> > > The best thing to do would perhaps to make __mro__ assignable, but
> > > with a check that ensures the above constraint. I think I'd take a
> > > patch for that.
> > Shouldn't be too hard.
> > > I'd also take a patch for assignable __bases__. Note that there are
> > > constraints between __bases__ and __base__.
> > Should assigning to __bases__ automatically tweak __mro__ and
> > __base__? Guess so.
> Yes. Note that changing __base__ should not be done lightly --
> basically, the old and new base must be layout compatible, exactly
> like for assignment to __class__.
OK. I can crib code from type_set_class, I guess. Or one could just
allow assignment to __bases__ when __base__ doesn't change? __base__
is object for the majority of new-style classes, isn't it?
Brr. There's a lot I don't know about post 2.2 typeobject.c.
> > What would assigning to __base__ do in isolation?
> > Perhaps that shouldn't be writeable.
> Perhaps it could be writable when __bases__ is a 1-tuple.
Don't see the point of that.
> But it's fine if it's not writable.
> > > I'd also take a patch for assignable __name__.
> > This is practically a one-liner, isn't it? Not hard, anyway.
> Probably. Can't remember why I didn't do it earlier.
It's a bit more complicated than that.
What's the deal wrt. dots in tp_name? Is there any way for a user
defined class to end up called "something.somthing_else"?
Oh, and while we're at it, here's a bogosity:
>>> class C(object):
>>> C.__module__ = 1
Traceback (most recent call last):
File "<stdin>", line 1, in ?
caused by lax testing in type_set_module.
> > And there was me wondering what I was going to do this evening.
> I don't have that problem -- a Zope customer problem was waiting for
> me today. :-(
Well, I didn't get it finished either. Fiddly, this stuff. Maybe by
The Internet is full. Go away.
[Since the last message triggered no response, I'm retrying.]
I have changes in my sandbox to incorporate bsddb3 into Python
proper. This essentially is a copy of bsddb3 3.4.0, with the following
- the extension module is called _bsddb (not bsddb3._db)
- the package is called bsddb (not bsddb3)
Both test_bsddb and test_anydbm continue to work unmodified.
Is it ok to commit these changes?
Are you PythonLabs folks aware of this? It might be interesting &&||
Em Software, Inc.
> -----Original Message-----
> From: Yahya H. Mirza [mailto:firstname.lastname@example.org]
> Sent: Wednesday, October 30, 2002 9:08 AM
> To: Corin Day
> Cc: Jürg Gutknecht; davidi(a)borland.com; Ralph Johnson; George
> Lippman; Yukihiro Matsumoto; eliot(a)parcplace.com; David Simmons;
> Sullivan; David Stutz; Dan Sugalski; ian.piumarta(a)inria.fr; David
> Shawn Woods; Misha Dmitriev; Jim Miller (COM+); Tony Williams; Dan Fay
> (RESEARCH); Mark Ryland; Andrew Palay; Mark Lewin; Don Syme; Greg
> Pierre Sainoyant; Van Eden; Alan Borning; chambers(a)cs.washington.edu;
> E. Fiuczynski; David Notkin; zahorjan(a)cs.washington.edu;
> jonal(a)cs.washington.edu; csk(a)cs.washington.edu; Brad Merrill; Brian
> Brian Foote
> Subject: LAR Workshop Website Online,
> I would like to invite you all to register for LAR02:
> Our workshop website is now online and it can be accessed either
> main OOPSLA Workshop page or directly via:
> If you would please take the time to Register even if you are
> and provide some feedback, I would greatly appreciate it.
> Our workshop starts at 8:45 AM this Monday November 4 at the OOPSLA
> Conference in the Seattle Convention Center in Rooms 613 - 614.
> Please feel free to invite whoever you think would be interested in
> Finally I would like to thank Cori Day for doing a wonderful job on
> Yahya H. Mirza
> Aurora Borealis Software
> 8502 166th Ave. NE
> Redmond WA, 98052
Guido van Rossum <guido(a)python.org> writes:
> > I guess one way of doing this would be to reimplement mro resolution
> > and so on in Python, which would be annoying and inefficient. Hmm.
> Alas, yes. You'd have to be able to write a class's tp_mro slot
> (corresponding to the __mro__ attribute), but there's no way to do
> that in Python, because it is too easy to cause mistakes. E.g. all
> C code that currently uses tp_mro assumes that it is a tuple whose
> items are either types or classic classes.
> The best thing to do would perhaps to make __mro__ assignable, but
> with a check that ensures the above constraint. I think I'd take a
> patch for that.
Shouldn't be too hard.
> I'd also take a patch for assignable __bases__. Note that there are
> constraints between __bases__ and __base__.
Should assigning to __bases__ automatically tweak __mro__ and
__base__? Guess so. What would assigning to __base__ do in isolation?
Perhaps that shouldn't be writeable.
> I'd also take a patch for assignable __name__.
This is practically a one-liner, isn't it? Not hard, anyway.
And there was me wondering what I was going to do this evening.
Now this is what I don't get. Nobody said absolutely anything
bad about anything. Yet it is always possible to just pull
random flames out of ones ass.