Python-Dev July 2001

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88 participants
199 discussions

RE: [Python-Dev] Those import related syntax errors again...

by Samuele Pedroni

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.

16 years, 11 months

Parrot -- should life imitate satire?

by Eric S. Raymond

The 2001 O'Reilly Open Source Convention, was, as usual, a very stimulating event and a forum for a lot of valuable high-level conversations between the principal developers of many open-source projects. Many of you know that I maintain friendly and relatively close relations with a number of senior Perl hackers, including both Larry Wall himself and others like Chip Salzenberg, Randall Schwartz, Tom Christiansen, Adam Turoff, and more recently Simon Cozens (who lurks on this list these days). At OSCon I believe I got a pretty good picture of what the leaders of the Perl community are thinking and planning these days. They have definitely come out of the slump they were in a year ago -- there's a much-renewed sense of energy over there. I think their plans offer both the Perl and Python communities some large strategic opportunities. Specifically, I'm urging the Python community's leadership to seriously explore the possibility of helping make the Parrot hoax into a working reality. I have discussed this with Guido by phone, and though he is skeptical about such an implementation being actually possible, he also thinks the idea has tremendous potential and says he is willing to support it in public. The Perl people have blocked out an architecture for Perl 6 that envisages a new bytecode level, designed and implemented from scratch. They're very serious about this; I participated in some discussions of the bytecode design (and, incidentally, argued that the bytecode should emulate a stack rather than a register machine because the cost/speed disparities that justify register architectures in hardware don't exist in a software VM). The Perl people are receptive -- indeed, some of them are actively pushing -- the idea that their new bytecode should not be Perl-specific. Dan Sugalski, the current lead for the bytecode interpreter project, has named it Parrot. At the Perl 6 talk I attended, Chip Salzenberg speculated in public about possibly supporting a common runtime for Perl, Python, Ruby, and Intercal(!). One of the things that makes this an unprecedented opportunity is that the design of Perl 6 is not yet set in stone -- and Larry has already shown a willingness to move it in a Pythonward direction. Syntactically, Perl 5's -> syntax is going away to be replaced by a Python-like dot with implicit dereferencing (and Larry said in public this was Python's influence, not Java's). The languages have of course converged in other ways recently -- Python's new lexical scoping actually brings it closer to Perl "use strict" semantics. I believe the way is open for Python's leading technical people to be involved as co-equals in the design and implementation of the Parrot bytecode interpreter. I have even detected some willingness to use Python's existing bytecode as a design model for Parrot, and perhaps even portions of the Python interpreter codebase! One bold but possibly workable proposal would be to offer Dan and the Parrot project the Python bytecode interpreter as a base for the Parrot code, and then be willing to incorporate whatever (probably relatively minor) extensions are needed to support Perl 6's primitives. Following my conversation with Guido, I've put doing an architectural comparison of the existing Python and Perl bytecodes at the top of my priority list. I'm flying to Taipei tomorrow and will have a lot of hours on airplanes with my laptop to do this. Committing a common runtime with Perl would mean relinquishing exclusive design control of our bytecode level, but the Perl people seem themselves willing to give up *their* exclusive control to make this work. It is rather remarkable how respectful of Python they have become, and I can't emphasize enough that I think they are truly ready for us to come to the project as equal partners. (One important place where I think everybody understands the Python side of the force would clearly win out in a final Parrot design is in the extension-and-embedding facilities. Perl XS is acknowledged to be a nasty mess. My guess is the Perl guys would drop it like a hot rock for our stuff -- that would be as clear a win for them as co-opting Perl-style regexps was for us.) I think the benefits of a successful unification at the bytecode level, together with Larry's willingness to Pythonify the upper level of Perl 6 a bit, could be vast -- both for the Python community in particular and for scripting-language users in general. 1. Mixed-language programming in Perl and Python could become almost seamless, with all that implies for both languages getting the use of each others' libraries. 2. The prospects for getting decent Python compilation to native code would improve if both the Python and Perl communities were strongly motivated to solve the bytecode-compilation problem. 3. More generally, the fact remains that Perl's user/developer base is still much larger than ours. Successful unification would co-opt a lot of that energy for Python. Because the brain drain between Perl and Python is pretty much unidirectional in Python's favor (a fact even the top Perl hackers ruefully acknowledge), I don't think we need worry about being subsumed in that larger community either. I think there is a wonderful opportunity here for the Python and Perl developers to lead the open-source world. If we can do a good Parrot design together, I think it will be hard for the smaller scripting language communities to resist its pull. Ultimately, the common Parrot runtime could become the open-source community's answer -- a very competititive answer -- to the common runtime Microsoft is pushing for .NET. I think trying to make Parrot work would be worth some serious effort. -- <a href="http://www.tuxedo.org/~esr/">Eric S. Raymond</a> The Bible is not my book, and Christianity is not my religion. I could never give assent to the long, complicated statements of Christian dogma. -- Abraham Lincoln

20 years, 5 months

Re: [Python-Dev] CVS build breakage: snprintf finds its way into socketmodule.c

by Alex Coventry

> Following itojun's proposal, I have now added an autoconf test for > snprintf, and use sprintf if it is not available. In PySocket_getaddrinfo, would it make sense to increase the allocation of pbuf from 10 characters to, say, 30 characters, in case sprintf(pbuf, "%ld", PyInt_AsLong(pobj)); gets run on a 64-bit machine? Alex.

20 years, 5 months

BEGIN_ALLOW_THREADS

by Martin Sj�gren

Hello Is there a reason the Py_BEGIN_ALLOW_THREADS and Py_END_ALLOW_THREADS don't allow an argument specifying what variable to save the state to? I needed this myself so I wrote the following: #ifdef WITH_THREAD # define MY_BEGIN_ALLOW_THREADS(st) \ { st = PyEval_SaveThread(); } # define MY_END_ALLOW_THREADS(st) \ { PyEval_RestoreThread(st); st = NULL; } #else # define MY_BEGIN_ALLOW_THREADS(st) # define MY_END_ALLOW_THREADS(st) { st = NULL; } #endif It works just fine but has one drawback: Whenever Py_BEGIN_ALLOW_THREADS changes, I have to change my macros too. Wouldn't it be reasonable to supply two sets of macros, one that allows exactly this, and one that does what Py_BEGIN_ALLOW_THREADS currently does. Martin Sjögren -- Martin Sjögren martin(a)strakt.com ICQ : 41245059 Phone: +46 (0)31 405242 Cell: +46 (0)739 169191 GPG key: http://www.strakt.com/~martin/gpg.html

20 years, 5 months

cgitb.py for Python 2.2

by Ka-Ping Yee

Hi guys. Sorry i've been fairly quiet recently -- at least life isn't dull. I wanted to put in a few words for cgitb.py for your consideration. I think you all saw it at IPC 9 -- if you missed the presentation, there are examples at http://www.lfw.org/python to check out. What i'm proposing is that we toss cgitb.py into the standard library (pretty small at about 100 lines, since all the heavy lifting is in pydoc and inspect). Then we can add this to site.py: if os.environ.has_key("GATEWAY_INTERFACE"): import sys, cgitb sys.excepthook = cgitb.excepthook I think this is pretty safe, since GATEWAY_INTERFACE is guaranteed to exist under the CGI specification and should never appear in any other context. cgitb.py is written in paranoid fashion -- if anything goes wrong during generation of the HTML traceback, sys.stderr still goes to the browser; and if for some reason the page gets dumped to a shell somewhere, the original traceback is still visible in a comment at the end of the page. The upside is that we *automagically* get pretty tracebacks for all the Python CGI scripts there, with zero effort from the CGI script writers. I think this is a really strong hook for people getting started with Python. No more "internal server error" messages followed by the annoying task of inserting "print 'Content-Type: text/html\n\n<pre>'" into all your scripts! As for me, i've probably done this hundreds of times now, and would love to stop doing it. I anticipate a possible security concern (as this shows bits of your source code to strangers when problems happen). So i have tried to address that by providing a SECRET flag in cgitb that causes the tracebacks to get written to files instead of the Web browser. Opinions and suggestions are welcomed! (I'm looking at the good stuff that the WebWare people have done with it, and i plan to merge in their improvements. For the HTML-heads out there in particular, i'm looking for your thoughts on the reset() routine.) -- ?!ng

20 years, 5 months

Good news about ExtensionClass and Python 2.2a1

by Neil Schemenauer

After a few tweaks to ExtensionClass and a few small fixes to some of our introspection code I'm happy to say that Python 2.2a1 passes our unit test suite. This is significant since there are about 45000 lines of code (counted by "wc -l") tested by 3569 test cases. Since we use ZODB ExtensionClasses are quite widely used. Merging descr_branch into HEAD sounds like a good idea to me. Well done Guido. I'm going to spend a bit of time trying to rewrite the ZODB Persistent class as a type. Attached is a diff of the changes I made to ExtensionClass. Neil --- ExtensionClass.h.dist Tue Jul 31 11:50:39 2001 +++ ExtensionClass.h Tue Jul 31 12:15:21 2001 @@ -143,12 +143,48 @@ reprfunc tp_str; getattrofunc tp_getattro; setattrofunc tp_setattro; - /* Space for future expansion */ - long tp_xxx3; - long tp_xxx4; + + /* Functions to access object as input/output buffer */ + PyBufferProcs *tp_as_buffer; + + /* Flags to define presence of optional/expanded features */ + long tp_flags; char *tp_doc; /* Documentation string */ + /* call function for all accessible objects */ + traverseproc tp_traverse; + + /* delete references to contained objects */ + inquiry tp_clear; + + /* rich comparisons */ + richcmpfunc tp_richcompare; + + /* weak reference enabler */ + long tp_weaklistoffset; + + /* Iterators */ + getiterfunc tp_iter; + iternextfunc tp_iternext; + + /* Attribute descriptor and subclassing stuff */ + struct PyMethodDef *tp_methods; + struct memberlist *tp_members; + struct getsetlist *tp_getset; + struct _typeobject *tp_base; + PyObject *tp_dict; + descrgetfunc tp_descr_get; + descrsetfunc tp_descr_set; + long tp_dictoffset; + initproc tp_init; + allocfunc tp_alloc; + newfunc tp_new; + destructor tp_free; /* Low-level free-memory routine */ + PyObject *tp_bases; + PyObject *tp_mro; /* method resolution order */ + PyObject *tp_defined; + #ifdef COUNT_ALLOCS /* these must be last */ int tp_alloc; @@ -302,7 +338,9 @@ { PyExtensionClassCAPI->Export(D,N,&T); } /* Convert a method list to a method chain. */ -#define METHOD_CHAIN(DEF) { DEF, NULL } +#define METHOD_CHAIN(DEF) \ + 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, \ + { DEF, NULL } /* The following macro checks whether a type is an extension class: */ #define PyExtensionClass_Check(TYPE) \ @@ -336,7 +374,9 @@ #define PURE_MIXIN_CLASS(NAME,DOC,METHODS) \ static PyExtensionClass NAME ## Type = { PyObject_HEAD_INIT(NULL) \ 0, # NAME, sizeof(PyPureMixinObject), 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \ - 0, 0, 0, 0, 0, 0, 0, DOC, {METHODS, NULL}, \ + 0, 0, 0, 0, 0, 0, 0, DOC, \ + 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, \ + {METHODS, NULL}, \ EXTENSIONCLASS_BASICNEW_FLAG} /* The following macros provide limited access to extension-class --- ExtensionClass.c.dist Tue Jul 31 11:01:20 2001 +++ ExtensionClass.c Tue Jul 31 12:15:24 2001 @@ -119,7 +119,7 @@ static PyObject *subclass_watcher=0; /* Object that subclass events */ static void -init_py_names() +init_py_names(void) { #define INIT_PY_NAME(N) py ## N = PyString_FromString(#N) INIT_PY_NAME(__add__); @@ -1800,8 +1800,8 @@ if (PyFunction_Check(r) || NeedsToBeBound(r)) ASSIGN(r,newPMethod(self,r)); - else if (PyMethod_Check(r) && ! PyMethod_Self(r)) - ASSIGN(r,newPMethod(self, PyMethod_Function(r))); + else if (PyMethod_Check(r) && ! PyMethod_GET_SELF(r)) + ASSIGN(r,newPMethod(self, PyMethod_GET_FUNCTION(r))); return r; } @@ -3527,7 +3527,7 @@ }; void -initExtensionClass() +initExtensionClass(void) { PyObject *m, *d; char *rev="$Revision: 1.1 $";

20 years, 5 months

Python API version & optional features

by M.-A. Lemburg

Martin has uploaded a patch which modifies the Python API level number depending on the setting of the compile time option for internal Unicode width (UCS-2/UCS-4): https://sourceforge.net/tracker/?func=detail&aid=445717&group_id=5470&atid=… I am not sure whether this is the right way to approach this problem, though, since it affects all extensions -- not only ones using Unicode. If at all possible, I'd prefer some other means to handle this situation (extension developers are certainly not going to start shipping binaries for narrow and wide Python versions if their extension does not happen to use Unicode). Any ideas ? Thanks, -- Marc-Andre Lemburg CEO eGenix.com Software GmbH ______________________________________________________________________ Consulting & Company: http://www.egenix.com/ Python Software: http://www.lemburg.com/python/

20 years, 5 months

PyOS_snprintf() / PyOS_vsnprintf()

by M.-A. Lemburg

Just to let you know and to initiate some cross-platform testing: While working on the warning patch for modsupport.c, I've added two new APIs which hopefully make it easier for Python to switch to buffer overflow safe [v]snprintf() APIs for error reporting et al. The two new APIs are PyOS_snprintf() and PyOS_vsnprintf() and work just like the standard ones in many C libs. On platforms which have snprintf(), the native APIs are used, on all other an emulation with snprintf() tries to do its best. Please try them out on your platform. If all goes well, I think we should replace all sprintf() (without the n in the name) with these new safer APIs. Thanks, -- Marc-Andre Lemburg CEO eGenix.com Software GmbH ______________________________________________________________________ Company & Consulting: http://www.egenix.com/ Python Software: http://www.lemburg.com/python/

20 years, 5 months

Revised decimal type PEP

by Michael McLay

PEP: 2XX Title: Adding a Decimal type to Python Version: $Revision:$ Author: mclay(a)nist.gov <mclay(a)nist.gov> Status: Draft Type: ?? Created: 25-Jul-2001 Python-Version: 2.2 Introduction This PEP describes the addition of a decimal number type to Python. Rationale The original Python numerical model included int, float, and long. By popular request the imaginary type was added to improve support for engineering and scientific applications. The addition of a decimal number type to Python will improve support for business applications as well as improve the utility of Python a teaching language. The number types currently used in Python are encoded as base two binary numbers. The base 2 arithmetic used by binary numbers closely approximates the decimal number system and for many applications the differences in the calculations are unimportant. The decimal number type encodes numbers as decimal digits and use base 10 arithmetic. This is the number system taught to the general public and it is the system used by businesses when making financial calculations. For financial and accounting applications the difference between binary and decimal types is significant. Consequently the computer languages used for business application development, such as COBOL, use decimal types. The decimal number type meets the expectations of non-computer scientists when making calculations. For these users the rounding errors that occur when using binary numbers is a source of confusion and irritation. Implementation The tokenizer will be modified to recognized number literals with a 'd' suffix and a decimal() function will be added to __builtins__. A decimal number can be used to represent integers and floating point numbers and decimal numbers can also be displayed using scientific notation. Examples of decimal numbers include: 1234d -1234d 1234.56d -1234.56d 1234.56e2d -1234.56e-2d The type returned by either a decimal floating point or a decimal integer is the same: >>> type(12.2d) <type 'decimal'> >>> type(12d) <type 'decimal'> >>> type(-12d+12d) <type 'decimal'> >>> type(12d+12.0d) <type 'decimal'> This proposal will also add an optional 'b' suffix to the representation of binary float type literals and binary int type literals. >>> float(12b) 12.0 >>> type(12.2b) <type 'float'> >>> type(float(12b)) <type 'float'> >>> type(12b) <type 'int'> The decimal() conversion function added to __builtins__ will support conversions of strings, and binary types to decimal. >>> type(decimal("12d")) <type 'decimal'> >>> type(decimal("12")) <type 'decimal'> >>> type(decimal(12b)) <type 'decimal'> >>> type(decimal(12.0b)) <type 'decimal'> >>> type(decimal(123456789123L)) <type 'decimal'> The conversion functions int() and float() in the __builtin__ module will support conversion of decimal numbers to the binary number types. >>> type(int(12d)) <type 'int'> >>> type(float(12.0d)) <type 'float'> Expressions that mix integers with decimals will automatically convert the integer to decimal and the result will be a decimal number. >>> type(12d + 4b) <type 'decimal'> >>> type(12b + 4d) <type 'decimal'> >>> type(12d + len('abc')) <type 'decimal'> >>> 3d/4b 0.75 Expressions that mix binary floats with decimals introduce the possibility of unexpected results because the two number types use different internal representations for the same numerical value. The severity of this problem is dependent on the application domain. For applications that normally use binary numbers the error may not be important and the conversion should be done silently. For newbie programmers a warning should be issued so the newbie will be able to locate the source of a discrepancy between the expected results and the results that were achieved. For financial applications the mixing of floating point with binary numbers should raise an exception. To accommodate the three possible usage models the python interpreter command line options will be used to set the level for warning and error messages. The three levels are: promiscuous mode, -f or --promiscuous safe mode -s or --save pedantic mode -p or --pedantic The default setting will be set to the safe setting. In safe mode mixing decimal and binary floats in a calculation will trigger a warning message. >>> type(12.3d + 12.2b) Warning: the calculation mixes decimal numbers with binary floats <type 'decimal'> In promiscuous mode warnings will be turned off. >>> type(12.3d + 12.2b) <type 'decimal'> In pedantic mode warning from safe mode will be turned into exceptions. >>> type(12.3d + 12.2b) Traceback (innermost last): File "<stdin>", line 1, in ? TypeError: the calculation mixes decimal numbers with binary floats Semantics of Decimal Numbers ??

20 years, 5 months

Re: [Python-Dev] Changing the Division Operator -- PEP 238, rev 1.12

by Michael Hudson

Samuele Pedroni <pedroni(a)inf.ethz.ch> writes: > ... > > > > > > > > Does codeop currently work in Jython? The solution should continue to > > > > work in Jython then. > > > We have our interface compatible version of codeop that works. > > > > Would implementing the new interfaces I sketched out for codeop.py be > > possible in Jython? That's the bit I care about, not so much the > > interface to __builtin__.compile. > Yes, it's of possible. Good; hopefully we can get somewhere then. > > > > Does Jython support the same flag bit values as > > > > CPython? If not, Paul Prescod's suggestion to use keyword arguments > > > > becomes very relevant. > > > we support a subset of the co_flags, CO_NESTED e.g. is there with the same > > > value. > > > > > > But the embedding API is very different, my implementation of nested > > > scopes does not define any Py_CF... flags, we have an internal CompilerFlags > > > object but is more similar to PyFutureFeatures ... > > > > Is this object exposed to Python code at all? > Not publicily, but in Jython the separating line is a bit different, > because public java classes are always accessible from jython, > even most of the internals. That does not mean and every use of that > is welcome and supported. Ah, of course. I'd forgotten how cool Jython was in some ways. > > One approach would be > > PyObject-izing PyFutureFlags and making *that* the fourth argument to > > compile... > > > > class Compiler: > > def __init__(self): > > self.ff = ff.new() # or whatever > > def __call__(self, source, filename, start_symbol): > > code = compile(source, filename, start_symbol, self.ff) > > self.ff.merge(code.co_flags) > > return code > I see, "internally" we already have a compiler_flags function > that do the same of: > > code = compile(source, filename, start_symbol, self.ff) > > self.ff.merge(code.co_flags) > > where self.ff is a CompuilerFlags object. > > I can re-arrange things for any interface, Well, I don't want to make more work for you - I imagine Guido's doing enough of that for two! > I was only trying to explain our approach and situation and a > possible way to avoid duplicating some internal code in Python. Can you point me to the code in CVS that implements this sort of thing? I don't really know Java but I can probably muddle through to some extent. We might as well have CPython copy Jython for once... Cheers, M. -- On the other hand, the following areas are subject to boycott in reaction to the rampant impurity of design or execution, as determined after a period of study, in no particular order: ... http://www.naggum.no/profile.html

20 years, 5 months

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Python-Dev July 2001