Mailman 3 December 2002 - Python-Dev

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

May 18, 2021

It has been a while since I posted a copy of PEP 1 to the mailing lists and newsgroups. I've recently done some updating of a few sections, so in the interest of gaining wider community participation in the Python development process, I'm posting the latest revision of PEP 1 here. A version of the PEP is always available on-line at http://www.python.org/peps/pep-0001.html Enjoy, -Barry -------------------- snip snip -------------------- PEP: 1 Title: PEP Purpose and Guidelines Version: $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

RE: [Python-Dev] Those import related syntax errors again...
by Samuele Pedroni Feb. 23, 2005

Feb. 23, 2005

Hi. [Mark Hammond] > 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 > cause. > > 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.] [GvR] > > 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: <frag> y=3 def f(): y=9 exec "y=2" def g(): return y return y,g() print f() </frag> What should this print? the situation leads not to a canonical solution as class def scopes. or <frag> def f(): from foo import * def g(): return y return g() print f() </frag> [Mark Hammond] > > 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 confusion. [Andrew Kuchling] > >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.

18 78

Extension modules, Threading, and the GIL
by David Abrahams Jan. 12, 2003

Jan. 12, 2003

Recently an issue has come up on the C++-sig which I think merits a little attention here. To boil it down, the situation looks like this: Shared library Q uses threading but not Python. It supplies a an interface by which users can supply callback functions. Some of these callbacks will be invoked directly in response to external calls into Q; others will be invoked on threads started by calls into Q. Python extension module A calls shared library Q, but doesn't use its callback interface. It works fine by itself. Python extension module B calls shared library Q and uses Q's callback interface. Because some of the callbacks need to use the Python API, and *might* be invoked by threads, they must all acquire the GIL. Because they also might be invoked by direct calls into Q, B must always release the GIL before calling anything in Q. Problem: using B while A is loaded breaks A: because B has installed callbacks in Q that acquire the GIL, A must also release the GIL before calling into Q. Notice that the author of A may have had no reason to believe anyone would install Python callbacks in Q! It seems to me that for situations like these, where a function may or may not be called on Python's main thread, it would be helpful if Python supplied a "recursive mutex" GIL acquisition/release pair, for which acquisition and release on the main thread would simply bump a counter. Is this something that was considered and rejected? TIA, Dave -- David Abrahams dave(a)boost-consulting.com * http://www.boost-consulting.com Boost support, enhancements, training, and commercial distribution

14 81

PEP: Support for System Upgrades
by M.-A. Lemburg Jan. 7, 2003

Jan. 7, 2003

PEP: 0??? Title: Support for System Upgrades Version: $Revision: 0.0 $ Author: mal(a)lemburg.com (Marc-Andr? Lemburg) Status: Draft Type: Standards Track Python-Version: 2.3 Created: 19-Jul-2001 Post-History: Abstract 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. Problem 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 configuration. 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. Proposed Solutions This PEP proposes two different but not necessarily conflicting solutions: 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 $stdlibpath/system-packages) * 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. Scope Solution 1: Python 2.3 and up Solution 2: all Python versions supported by distutils Credits None References None Copyright This document has been placed in the public domain. Local Variables: mode: indented-text indent-tabs-mode: nil End: -- Marc-Andre Lemburg 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/

4 13

GC at exit?
by Aahz Jan. 3, 2003

Jan. 3, 2003

[Originally posted to comp.lang.python with no response; asking here before filing a bug report] Is garbage collection supposed to run when Python exits? The following program does not print any output, unless I uncomment the gc.collect() (or add a for loop that forces GC after creating the cycle): import gc class A: pass class B: def __del__(self): print "Bye-bye!" a = A() b = A() a.b = b b.a = a a.x = B() del a del b #gc.collect() -- Aahz (aahz(a)pythoncraft.com) <*> http://www.pythoncraft.com/ "I disrespectfully agree." --SJM

8 11

RE: [Python-checkins] python/dist/src/Modules _randommodule.c,1.1,1.2
by Tim Peters Jan. 3, 2003

Jan. 3, 2003

[nnorwitz(a)users.sourceforge.net] > Modified Files: > _randommodule.c > Log Message: > Try to get compilation working for cygwin > > Index: _randommodule.c And then, for example, before: > ! PyObject_GenericGetAttr, /*tp_getattro*/ and after: > ! 0, /*tp_getattro*/ followed by: > + Random_Type.tp_getattro = PyObject_GenericGetAttr; > + Random_Type.tp_alloc = PyType_GenericAlloc; > + Random_Type.tp_free = _PyObject_Del; in the module init function. Please don't make this kind of change -- it makes the code so much harder to follow. If this is needed for Cygwin, then, e.g., do #define DEFERRED(x) 0 /* some boxes can't resolve addresses at compile-time */ and make the "after" line DEFERRED(PyObject_GenericGetAttr), /*tp_getattro*/ IOW, the type slots should be readable on their own, as a static unit.

6 9

PEP 303: Extend divmod() for Multiple Divisors
by Thomas Bellman Jan. 2, 2003

Jan. 2, 2003

I humbly submit this PEP for your dissection. As I am not subscribed to python-dev, please make sure that your comments are CC:ed to <bellman+pep-divmod(a)lysator.liu.se>, so I can see them. I have also posted this to comp.lang.python. I have written an implementation also, but I need to check it some more to see if I've got the reference counting correct before I dare post it. :-) PEP: 303 Title: Extend divmod() for Multiple Divisors Version: $Revision: 1.2 $ Last-Modified: $Date: 2002/12/31 16:02:49 $ Author: Thomas Bellman <bellman+pep-divmod(a)lysator.liu.se> Status: Draft Type: Standards Track Content-Type: text/plain Created: 31-Dec-2002 Python-Version: 2.3 Post-History: Abstract This PEP describes an extension to the built-in divmod() function, allowing it to take multiple divisors, chaining several calls to divmod() into one. Specification The built-in divmod() function would be changed to accept multiple divisors, changing its signature from divmod(dividend, divisor) to divmod(dividend, *divisors). The dividend is divided by the last divisor, giving a quotient and a remainder. The quotient is then divided by the second to last divisor, giving a new quotient and remainder. This is repeated until all divisors have been used, and divmod() then returns a tuple consisting of the quotient from the last step, and the remainders from all the steps. A Python implementation of the new divmod() behaviour could look like: def divmod(dividend, *divisors): modulos = () q = dividend while divisors: q,r = q.__divmod__(divisors[-1]) modulos = (r,) + modulos divisors = divisors[:-1] return (q,) + modulos Motivation Occasionally one wants to perform a chain of divmod() operations, calling divmod() on the quotient from the previous step, with varying divisors. The most common case is probably converting a number of seconds into weeks, days, hours, minutes and seconds. This would today be written as: def secs_to_wdhms(seconds): m,s = divmod(seconds, 60) h,m = divmod(m, 60) d,h = divmod(h, 24) w,d = divmod(d, 7) return (w,d,h,m,s) This is tedious and easy to get wrong each time you need it. If instead the divmod() built-in is changed according the proposal, the code for converting seconds to weeks, days, hours, minutes and seconds then become def secs_to_wdhms(seconds): w,d,h,m,s = divmod(seconds, 7, 24, 60, 60) return (w,d,h,m,s) which is easier to type, easier to type correctly, and easier to read. Other applications are: - Astronomical angles (declination is measured in degrees, minutes and seconds, right ascension is measured in hours, minutes and seconds). - Old British currency (1 pound = 20 shilling, 1 shilling = 12 pence) - Anglo-Saxon length units: 1 mile = 1760 yards, 1 yard = 3 feet, 1 foot = 12 inches. - Anglo-Saxon weight units: 1 long ton = 160 stone, 1 stone = 14 pounds, 1 pound = 16 ounce, 1 ounce = 16 dram - British volumes: 1 gallon = 4 quart, 1 quart = 2 pint, 1 pint = 20 fluid ounces Rationale The idea comes from APL, which has an operator that does this. (I don't remember what the operator looks like, and it would probably be impossible to render in ASCII anyway.) The APL operator takes a list as its second operand, while this PEP proposes that each divisor should be a separate argument to the divmod() function. This is mainly because it is expected that the most common uses will have the divisors as constants right in the call (as the 7, 24, 60, 60 above), and adding a set of parentheses or brackets would just clutter the call. Requiring an explicit sequence as the second argument to divmod() would seriously break backwards compatibility. Making divmod() check its second argument for being a sequence is deemed to be too ugly to contemplate. And in the case where one *does* have a sequence that is computed other-where, it is easy enough to write divmod(x, *divs) instead. Requiring at least one divisor, i.e rejecting divmod(x), has been considered, but no good reason to do so has come to mind, and is thus allowed in the name of generality. Calling divmod() with no divisors should still return a tuple (of one element). Code that calls divmod() with a varying number of divisors, and thus gets a return value with an "unknown" number of elements, would otherwise have to special case that case. Code that *knows* it is calling divmod() with no divisors is considered to be too silly to warrant a special case. Processing the divisors in the other direction, i.e dividing with the first divisor first, instead of dividing with the last divisor first, has been considered. However, the result comes with the most significant part first and the least significant part last (think of the chained divmod as a way of splitting a number into "digits", with varying weights), and it is reasonable to specify the divisors (weights) in the same order as the result. The inverse operation: def inverse_divmod(seq, *factors): product = seq[0] for x,y in zip(factors, seq[1:]): product = product * x + y return product could also be useful. However, writing seconds = (((((w * 7) + d) * 24 + h) * 60 + m) * 60 + s) is less cumbersome both to write and to read than the chained divmods. It is therefore deemed to be less important, and its introduction can be deferred to its own PEP. Also, such a function needs a good name, and the PEP author has not managed to come up with one yet. Calling divmod("spam") does not raise an error, despite strings supporting neither division nor modulo. However, unless we know the other object too, we can't determine whether divmod() would work or not, and thus it seems silly to forbid it. Backwards Compatibility Any module that replaces the divmod() function in the __builtin__ module, may cause other modules using the new syntax to break. It is expected that this is very uncommon. Code that expects a TypeError exception when calling divmod() with anything but two arguments will break. This is also expected to be very uncommon. No other issues regarding backwards compatibility are known. Reference Implementation Not finished yet, but it seems a rather straightforward new implementation of the function builtin_divmod() in Python/bltinmodule.c Copyright This document has been placed in the public domain. -- Thomas Bellman, Lysator Computer Club, Linköping University, Sweden "Adde parvum parvo magnus acervus erit" ! bellman @ lysator.liu.se (From The Mythical Man-Month) ! Make Love -- Nicht Wahr!

12 21

Encoding file for KOI8-U
by Max Ischenko Jan. 2, 2003

Jan. 2, 2003

I wonder, whether koi8-u.py would be included in Python 2.3? If not, I could submit one. Though I'm not the author, it seems correct. -- Bst rgrds, M.A.X.: Mechanical Artificial Xenomorph.

2 2

bugs in stdlib
by Neal Norwitz Jan. 2, 2003

Jan. 2, 2003

Here's some problems I found in the stdlib. I already fixed one problem in ConfigParser, but I'm not sure it's correct. Lib/cgitb.py:202: No global (path) found Lib/cgitb.py:204: No global (path) found Lib/ConfigParser.py:581: Invalid arguments to (__init__), got 1, expected 4 Lib/imaplib.py:444: No global (root) found Lib/pprint.py:118: Invalid arguments to (format), got 3, expected 4 Lib/pprint.py:121: Invalid arguments to (format), got 3, expected 4 Neal

8 23

Python 2.3a1 released
by Guido van Rossum Dec. 31, 2002

Dec. 31, 2002

I'm happy to announce the successful release of Python 2.3a1 tonight, on Dec 31 (in *some* timezones :-). Go pick it up from its home page: http://www.python.org/2.3/ This is an alpha release: if you have Python code that's important (to you), please test it thoroughly with this release, but don't use the release for production runs. Please report any problems to the SourceForge bug tracker: http://sourceforge.net/bugs/?group_id=5470 What's new? The language isn't changing much this time. Instead, we have lots of new or improved standard library modules: bsddb, bz2, datetime, heapq, logging, optparse, ossaudiodev, random (Mersenne Twister algorithm), sets, socket (added timeouts), textwrap, and zipimport. That's right, you can now import modules from zip files. More elaborate news is on the website: http://www.python.org/2.3/highlights.html (brief) http://www.python.org/doc/2.3a1/whatsnew/ (extensive) http://www.python.org/2.3/NEWS.html (exhausting) --Guido van Rossum (home page: http://www.python.org/~guido/)

1 0