Mailman 3 March 2001 - Python-Dev

Very recent test_global failure
by Tim Peters March 1, 2001

March 1, 2001

Windows. > python ../lib/test/regrtest.py test_global test_global <test code>:2: SyntaxWarning: name 'a' is assigned to before global declaration <test code>:2: SyntaxWarning: name 'b' is assigned to before global declaration The actual stdout doesn't match the expected stdout. This much did match (between asterisk lines): ********************************************************************** test_global ********************************************************************** Then … [View More]

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Is outlawing-nested-import-* only an implementation issue?
by Ka-Ping Yee March 1, 2001

March 1, 2001

Hi all -- i've been reading the enormous thread on nested scopes with some concern, since i would very much like Python to support "proper" lexical scoping, yet i also care about compatibility. There is something missing from my understanding here: - The model is, each environment has a pointer to the enclosing environment, right? - Whenever you can't find what you're looking for, you go up to the next level and keep looking, right? - So what's the issue with not … [View More]being able to determine which variable binds in which scope? With the model just described, it's perfectly clear. Is all this breakage only caused by the particular optimizations for lookup in the implementation (fast locals, etc.)? Or have i missed something obvious? I could probably go examine the source code of the nested scoping changes to find the answer to my own question, but in case others share this confusion with me, i thought it would be worth asking. * * * Consider for a moment the following simple model of lookup: 1. A scope maps names to objects. 2. Each scope except the topmost also points to a parent scope. 3. To look up a name, first ask the current scope. 4. When lookup fails, go up to the parent scope and keep looking. I believe the above rules are common among many languages and are commonly understood. The only Python-specific parts are then: 5. The current scope is determined by the nearest enclosing 'def'. 6. These statements put a binding into the current scope: assignment (=), def, class, for, except, import And that's all. * * * Given this model, all of the scoping questions that have been raised have completely clear answers: Example I >>> y = 3 >>> def f(): ... print y ... >>> f() 3 Example II >>> y = 3 >>> def f(): ... print y ... y = 1 ... print y ... >>> f() 3 1 >>> y 3 Example III >>> y = 3 >>> def f(): ... exec "y = 2" ... def g(): ... return y ... return g() ... >>> f() 2 Example IV >>> m = open('foo.py', 'w') >>> m.write('x = 1') >>> m.close() >>> def f(): ... x = 3 ... from foo import * ... def g(): ... print x ... g() ... >>> f() 1 In Example II, the model addresses even the current situation that sometimes surprises new users of Python. Examples III and IV are the current issues of contention about nested scopes. * * * It's good to start with a simple model for the user to understand; the implementation can then do funky optimizations under the covers so long as the model is preserved. So for example, if the compiler sees that there is no "import *" or "exec" in a particular scope it can short-circuit the lookup of local variables using fast locals. But the ability of the compiler to make this optimization should only affect performance, not affect the Python language model. The model described above is the approximately the one available in Scheme. It exactly reflects the environment-diagram model of scoping as taught to most Scheme students and i would argue that it is the easiest to explain. Some implementations of Scheme, such as STk, do what is described above. UMB scheme does what Python does now: the use-before-binding of 'y' in Example II would cause an error. I was surprised that these gave different behaviours; it turns out that the Scheme standard actually forbids the use of internal defines not at the beginning of a function body, thus sidestepping the issue. But we can't do this in Python; assignment must be allowed anywhere. Given that internal assignment has to have some meaning, the above meaning makes the most sense to me. -- ?!ng [View Less]

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Re: [Python-Dev] just trying to catch up with the semantic
by Samuele Pedroni March 1, 2001

March 1, 2001

Hi. Your rationale sounds ok. We are just facing the oddities of the python rule - that assignment indetifies locals - when extended to nested scopes new world. (Everybody will be confused his own way ;), better write non confusing code ;)) I think I should really learn to read code this way, and also everybody coming from languages with explicit declarations: is the semantic (expressed through bytecode instrs) right? (I) from __future__ import nested_scopes x=7 def f(): #… [View More]

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Finally, a Python Cookbook!
by David Ascher March 1, 2001

March 1, 2001

Hello all -- ActiveState is now hosting a site (http://www.ActiveState.com/PythonCookbook) that will be the beginning of a series of community-based language-specific cookbooks to be jointly sponsored by ActiveState and O'Reilly. The first in the series is the "Python Cookbook". We will be announcing this effort at the Python Conference, but wanted to give you a sneak peek at it ahead of time. The idea behind it is for it to be a managed open collaborative repository of Python recipes that … [View More]

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nested scopes and future status
by Jeremy Hylton March 1, 2001

March 1, 2001

There are several loose ends in the nested scopes changes that I won't have time to fix before the beta. Here's a laundry list of tasks that remain. I don't think any of these is crucial for the release. Holler if there's something you'd like me to fix tonight. - Integrate the parsing of future statements into the _symtable module's interface. This interface is new with 2.1 and undocumented, so it's deficiency here will not affect any code. - Update traceback.py to understand … [View More]

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Extensions that depend on .so's on Solaris
by Martin v. Loewis March 1, 2001

March 1, 2001

> I have a library "libenf.a", which depends on several .so's (Eric > Young's libeay and a couple of others). > My C module was pretty simple to put together. However, when I load > it, Python (or someone) complains that the symbols that I know are > in "libeay.so" are missing. If it says that the symbols are missing, it is *not* a problem of LD_LIBRARY_PATH, LD_RUN_PATH (I can't find documentation or mentioning of that variable anywhere...), or the -R option. Instead, the … [View More]

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Re: d = {}; d[0:1] = 1; d[0:1] = 2; print d[:]
by Guido van Rossum March 1, 2001

March 1, 2001

(Adding python-dev, keeping python-list) > Quoth Robin Thomas <robin.thomas(a)starmedia.net>: > | Using Python 2.0 on Win32. Am I the only person to be depressed by the > | following behavior now that __getitem__ does the work of __getslice__? > | > | Python 2.0 (#8, Oct 16 2000, 17:27:58) [MSC 32 bit (Intel)] on win32 > | >>> d = {} > | >>> d[0:1] = 1 > | >>> d > | {slice(0, 1, None): 1} > | > | And then, for more … [View More]depression: > | > | >>> d[0:1] = 2 > | >>> d > | {slice(0, 1, None): 1, slice(0, 1, None): 2} > | > | And then, for extra extra chagrin: > | > | >>> print d[0:1] > | Traceback (innermost last): > | File "<pyshell#11>", line 1, in ? > | d[0:1] > | KeyError: slice(0, 1, None) > > If it helps, you ruined my day. Mine too. :-) > | So, questions: > | > | 1) Is this behavior considered a bug by the BDFL or the community at large? I can't speak for the community, but it smells like a bug to me. > | If so, has a fix been conceived? Am I re-opening a long-resolved issue? No, and no. > | 2) If we're still open to proposed solutions, which of the following do you > | like: > | > | a) make slices hash and cmp as their 3-tuple (start,stop,step), > | so that if I accidentally set a slice object as a key, > | I can at least re-set it or get it or del it :) Good idea. The SF patch manager is always open. > | b) have dict.__setitem__ expressly reject objects of SliceType > | as keys, raising your favorite in (TypeError, ValueError) This is *also* a good idea. > From: Donn Cave <donn(a)oz.net> > > I think we might be able to do better. I hacked in a quick fix > in ceval.c that looks to me like it has the desired effect without > closing the door to intentional slice keys (however unlikely.) [...] > *** Python/ceval.c.dist Thu Feb 1 14:48:12 2001 > --- Python/ceval.c Wed Feb 28 21:52:55 2001 > *************** > *** 3168,3173 **** > --- 3168,3178 ---- > /* u[v:w] = x */ > { > int ilow = 0, ihigh = INT_MAX; > + if (u->ob_type->tp_as_mapping) { > + PyErr_SetString(PyExc_TypeError, > + "dict object doesn't support slice assignment"); > + return -1; > + } > if (!_PyEval_SliceIndex(v, &ilow)) > return -1; > if (!_PyEval_SliceIndex(w, &ihigh)) Alas, this isn't right. It defeats the purpose completely: the whole point was that you should be able to write a sequence class that supports extended slices. This uses __getitem__ and __setitem__, but class instances have a nonzero tp_as_mapping pointer too! --Guido van Rossum (home page: http://www.python.org/~guido/) [View Less]

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Extensions that depend on .so's on Solaris
by Greg Wilson March 1, 2001

March 1, 2001

I'm working on Solaris, and have configured Python using --with-cxx=g++. I have a library "libenf.a", which depends on several .so's (Eric Young's libeay and a couple of others). I can't modify the library, but I'd like to wrap it so that our QA group can write scripts to test it. My C module was pretty simple to put together. However, when I load it, Python (or someone) complains that the symbols that I know are in "libeay.so" are missing. It's on LD_LIBRARY_PATH, and "nm" shows that the … [View More]

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__future__ and the interactive interpreter prompt
by Jeremy Hylton March 1, 2001

March 1, 2001

from __future__ import nested_scopes is accepted at the interactive interpreter prompt but has no effect beyond the line on which it was entered. You could use it with lambdas entered following a semicolon, I guess. I would rather see the future statement take effect for the remained of the interactive interpreter session. I have included a first-cut patch below that makes this possible, using an object called PySessionState. (I don't like the name, but don't have a better one; … [View More]PyCompilerFlags?) The idea of the session state is to record information about the state of an interactive session that may affect compilation. The state object is created in PyRun_InteractiveLoop() and passed all the way through to PyNode_Compile(). Does this seem a reasonable approach? Should I include it in the beta? Any name suggestions. Jeremy Index: Include/compile.h =================================================================== RCS file: /cvsroot/python/python/dist/src/Include/compile.h,v retrieving revision 2.27 diff -c -r2.27 compile.h *** Include/compile.h 2001/02/28 01:58:08 2.27 --- Include/compile.h 2001/03/01 18:18:27 *************** *** 41,47 **** /* Public interface */ struct _node; /* Declare the existence of this type */ ! DL_IMPORT(PyCodeObject *) PyNode_Compile(struct _node *, char *); DL_IMPORT(PyCodeObject *) PyCode_New( int, int, int, int, PyObject *, PyObject *, PyObject *, PyObject *, PyObject *, PyObject *, PyObject *, PyObject *, int, PyObject *); --- 41,48 ---- /* Public interface */ struct _node; /* Declare the existence of this type */ ! DL_IMPORT(PyCodeObject *) PyNode_Compile(struct _node *, char *, ! PySessionState *); DL_IMPORT(PyCodeObject *) PyCode_New( int, int, int, int, PyObject *, PyObject *, PyObject *, PyObject *, PyObject *, PyObject *, PyObject *, PyObject *, int, PyObject *); Index: Include/pythonrun.h =================================================================== RCS file: /cvsroot/python/python/dist/src/Include/pythonrun.h,v retrieving revision 2.38 diff -c -r2.38 pythonrun.h *** Include/pythonrun.h 2001/02/02 18:19:15 2.38 --- Include/pythonrun.h 2001/03/01 18:18:27 *************** *** 7,12 **** --- 7,16 ---- extern "C" { #endif + typedef struct { + int ss_nested_scopes; + } PySessionState; + DL_IMPORT(void) Py_SetProgramName(char *); DL_IMPORT(char *) Py_GetProgramName(void); *************** *** 25,31 **** DL_IMPORT(int) PyRun_SimpleString(char *); DL_IMPORT(int) PyRun_SimpleFile(FILE *, char *); DL_IMPORT(int) PyRun_SimpleFileEx(FILE *, char *, int); ! DL_IMPORT(int) PyRun_InteractiveOne(FILE *, char *); DL_IMPORT(int) PyRun_InteractiveLoop(FILE *, char *); DL_IMPORT(struct _node *) PyParser_SimpleParseString(char *, int); --- 29,35 ---- DL_IMPORT(int) PyRun_SimpleString(char *); DL_IMPORT(int) PyRun_SimpleFile(FILE *, char *); DL_IMPORT(int) PyRun_SimpleFileEx(FILE *, char *, int); ! DL_IMPORT(int) PyRun_InteractiveOne(FILE *, char *, PySessionState *); DL_IMPORT(int) PyRun_InteractiveLoop(FILE *, char *); DL_IMPORT(struct _node *) PyParser_SimpleParseString(char *, int); Index: Python/compile.c =================================================================== RCS file: /cvsroot/python/python/dist/src/Python/compile.c,v retrieving revision 2.184 diff -c -r2.184 compile.c *** Python/compile.c 2001/03/01 06:09:34 2.184 --- Python/compile.c 2001/03/01 18:18:28 *************** *** 471,477 **** static void com_assign(struct compiling *, node *, int, node *); static void com_assign_name(struct compiling *, node *, int); static PyCodeObject *icompile(node *, struct compiling *); ! static PyCodeObject *jcompile(node *, char *, struct compiling *); static PyObject *parsestrplus(node *); static PyObject *parsestr(char *); static node *get_rawdocstring(node *); --- 471,478 ---- static void com_assign(struct compiling *, node *, int, node *); static void com_assign_name(struct compiling *, node *, int); static PyCodeObject *icompile(node *, struct compiling *); ! static PyCodeObject *jcompile(node *, char *, struct compiling *, ! PySessionState *); static PyObject *parsestrplus(node *); static PyObject *parsestr(char *); static node *get_rawdocstring(node *); *************** *** 3814,3822 **** } PyCodeObject * ! PyNode_Compile(node *n, char *filename) { ! return jcompile(n, filename, NULL); } struct symtable * --- 3815,3823 ---- } PyCodeObject * ! PyNode_Compile(node *n, char *filename, PySessionState *sess) { ! return jcompile(n, filename, NULL, sess); } struct symtable * *************** *** 3844,3854 **** static PyCodeObject * icompile(node *n, struct compiling *base) { ! return jcompile(n, base->c_filename, base); } static PyCodeObject * ! jcompile(node *n, char *filename, struct compiling *base) { struct compiling sc; PyCodeObject *co; --- 3845,3856 ---- static PyCodeObject * icompile(node *n, struct compiling *base) { ! return jcompile(n, base->c_filename, base, NULL); } static PyCodeObject * ! jcompile(node *n, char *filename, struct compiling *base, ! PySessionState *sess) { struct compiling sc; PyCodeObject *co; *************** *** 3864,3870 **** } else { sc.c_private = NULL; sc.c_future = PyNode_Future(n, filename); ! if (sc.c_future == NULL || symtable_build(&sc, n) < 0) { com_free(&sc); return NULL; } --- 3866,3882 ---- } else { sc.c_private = NULL; sc.c_future = PyNode_Future(n, filename); ! if (sc.c_future == NULL) { ! com_free(&sc); ! return NULL; ! } ! if (sess) { ! if (sess->ss_nested_scopes) ! sc.c_future->ff_nested_scopes = 1; ! else if (sc.c_future->ff_nested_scopes) ! sess->ss_nested_scopes = 1; ! } ! if (symtable_build(&sc, n) < 0) { com_free(&sc); return NULL; } Index: Python/import.c =================================================================== RCS file: /cvsroot/python/python/dist/src/Python/import.c,v retrieving revision 2.169 diff -c -r2.169 import.c *** Python/import.c 2001/03/01 08:47:29 2.169 --- Python/import.c 2001/03/01 18:18:28 *************** *** 608,614 **** n = PyParser_SimpleParseFile(fp, pathname, Py_file_input); if (n == NULL) return NULL; ! co = PyNode_Compile(n, pathname); PyNode_Free(n); return co; --- 608,614 ---- n = PyParser_SimpleParseFile(fp, pathname, Py_file_input); if (n == NULL) return NULL; ! co = PyNode_Compile(n, pathname, NULL); PyNode_Free(n); return co; Index: Python/pythonrun.c =================================================================== RCS file: /cvsroot/python/python/dist/src/Python/pythonrun.c,v retrieving revision 2.125 diff -c -r2.125 pythonrun.c *** Python/pythonrun.c 2001/02/28 20:58:04 2.125 --- Python/pythonrun.c 2001/03/01 18:18:28 *************** *** 37,45 **** static void initmain(void); static void initsite(void); static PyObject *run_err_node(node *n, char *filename, ! PyObject *globals, PyObject *locals); static PyObject *run_node(node *n, char *filename, ! PyObject *globals, PyObject *locals); static PyObject *run_pyc_file(FILE *fp, char *filename, PyObject *globals, PyObject *locals); static void err_input(perrdetail *); --- 37,47 ---- static void initmain(void); static void initsite(void); static PyObject *run_err_node(node *n, char *filename, ! PyObject *globals, PyObject *locals, ! PySessionState *sess); static PyObject *run_node(node *n, char *filename, ! PyObject *globals, PyObject *locals, ! PySessionState *sess); static PyObject *run_pyc_file(FILE *fp, char *filename, PyObject *globals, PyObject *locals); static void err_input(perrdetail *); *************** *** 56,62 **** extern void _PyCodecRegistry_Init(void); extern void _PyCodecRegistry_Fini(void); - int Py_DebugFlag; /* Needed by parser.c */ int Py_VerboseFlag; /* Needed by import.c */ int Py_InteractiveFlag; /* Needed by Py_FdIsInteractive() below */ --- 58,63 ---- *************** *** 472,477 **** --- 473,481 ---- { PyObject *v; int ret; + PySessionState sess; + + sess.ss_nested_scopes = 0; v = PySys_GetObject("ps1"); if (v == NULL) { PySys_SetObject("ps1", v = PyString_FromString(">>> ")); *************** *** 483,489 **** Py_XDECREF(v); } for (;;) { ! ret = PyRun_InteractiveOne(fp, filename); #ifdef Py_REF_DEBUG fprintf(stderr, "[%ld refs]\n", _Py_RefTotal); #endif --- 487,493 ---- Py_XDECREF(v); } for (;;) { ! ret = PyRun_InteractiveOne(fp, filename, &sess); #ifdef Py_REF_DEBUG fprintf(stderr, "[%ld refs]\n", _Py_RefTotal); #endif *************** *** 497,503 **** } int ! PyRun_InteractiveOne(FILE *fp, char *filename) { PyObject *m, *d, *v, *w; node *n; --- 501,507 ---- } int ! PyRun_InteractiveOne(FILE *fp, char *filename, PySessionState *sess) { PyObject *m, *d, *v, *w; node *n; *************** *** 537,543 **** if (m == NULL) return -1; d = PyModule_GetDict(m); ! v = run_node(n, filename, d, d); if (v == NULL) { PyErr_Print(); return -1; --- 541,547 ---- if (m == NULL) return -1; d = PyModule_GetDict(m); ! v = run_node(n, filename, d, d, sess); if (v == NULL) { PyErr_Print(); return -1; *************** *** 907,913 **** PyRun_String(char *str, int start, PyObject *globals, PyObject *locals) { return run_err_node(PyParser_SimpleParseString(str, start), ! "<string>", globals, locals); } PyObject * --- 911,917 ---- PyRun_String(char *str, int start, PyObject *globals, PyObject *locals) { return run_err_node(PyParser_SimpleParseString(str, start), ! "<string>", globals, locals, NULL); } PyObject * *************** *** 924,946 **** node *n = PyParser_SimpleParseFile(fp, filename, start); if (closeit) fclose(fp); ! return run_err_node(n, filename, globals, locals); } static PyObject * ! run_err_node(node *n, char *filename, PyObject *globals, PyObject *locals) { if (n == NULL) return NULL; ! return run_node(n, filename, globals, locals); } static PyObject * ! run_node(node *n, char *filename, PyObject *globals, PyObject *locals) { PyCodeObject *co; PyObject *v; ! co = PyNode_Compile(n, filename); PyNode_Free(n); if (co == NULL) return NULL; --- 928,957 ---- node *n = PyParser_SimpleParseFile(fp, filename, start); if (closeit) fclose(fp); ! return run_err_node(n, filename, globals, locals, NULL); } static PyObject * ! run_err_node(node *n, char *filename, PyObject *globals, PyObject *locals, ! PySessionState *sess) { if (n == NULL) return NULL; ! return run_node(n, filename, globals, locals, sess); } static PyObject * ! run_node(node *n, char *filename, PyObject *globals, PyObject *locals, ! PySessionState *sess) { PyCodeObject *co; PyObject *v; ! if (sess) { ! fprintf(stderr, "session state: %d\n", ! sess->ss_nested_scopes); ! } ! /* XXX pass sess->ss_nested_scopes to PyNode_Compile */ ! co = PyNode_Compile(n, filename, sess); PyNode_Free(n); if (co == NULL) return NULL; *************** *** 986,992 **** n = PyParser_SimpleParseString(str, start); if (n == NULL) return NULL; ! co = PyNode_Compile(n, filename); PyNode_Free(n); return (PyObject *)co; } --- 997,1003 ---- n = PyParser_SimpleParseString(str, start); if (n == NULL) return NULL; ! co = PyNode_Compile(n, filename, NULL); PyNode_Free(n); return (PyObject *)co; } [View Less]

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Re: d = {}; d[0:1] = 1; d[0:1] = 2; print d[:]
by Jeremy Hylton March 1, 2001

March 1, 2001

>>>>> "RT" == Robin Thomas <robin.thomas(a)starmedia.net> writes: RT> Using Python 2.0 on Win32. Am I the only person to be depressed RT> by the following behavior now that __getitem__ does the work of RT> __getslice__? You may the only person to have tried it :-). RT> Python 2.0 (#8, Oct 16 2000, 17:27:58) [MSC 32 bit (Intel)] on win32 >>> d = {} >>> d[0:1] = 1 >>> d {slice(0, 1, None): 1} I think this should raise … [View More]

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