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Jeremy Hyltoned9e6442000-10-09 18:26:42 +00001What's New in Python 2.0c1?
Guido van Rossum61000331997-08-15 04:39:58 +00002===========================
3
Guido van Rossum8ed602b2000-09-01 22:34:33 +00004Below is a list of all relevant changes since release 1.6. Older
Guido van Rossumf2ffce02000-09-05 04:38:34 +00005changes are in the file HISTORY. If you are making the jump directly
6from Python 1.5.2 to 2.0, make sure to read the section for 1.6 in the
7HISTORY file! Many important changes listed there.
Guido van Rossum61000331997-08-15 04:39:58 +00008
Guido van Rossumf2ffce02000-09-05 04:38:34 +00009Alternatively, a good overview of the changes between 1.5.2 and 2.0 is
10the document "What's New in Python 2.0" by Kuchling and Moshe Zadka:
11http://starship.python.net/crew/amk/python/writing/new-python/.
Guido van Rossum1f83cce1997-10-06 21:04:35 +000012
Guido van Rossumf2ffce02000-09-05 04:38:34 +000013--Guido van Rossum (home page: http://www.pythonlabs.com/~guido/)
Guido van Rossum437cfe81999-04-08 20:17:57 +000014
15======================================================================
16
Jeremy Hyltoned9e6442000-10-09 18:26:42 +000017What's new in 2.0 release candidate 1 (since beta 2)?
18=====================================================
19
Jeremy Hylton6040aaa2000-10-09 21:27:22 +000020What is release candidate 1?
21
22We believe that release candidate 1 will fix all known bugs that we
23intend to fix for the 2.0 final release. This release should be a bit
24more stable than the previous betas. We would like to see even more
25widespread testing before the final release, so we are producing this
26release candidate. The final release will be exactly the same unless
27any show-stopping (or brown bag) bugs are found by testers of the
28release candidate.
29
Jeremy Hyltoned9e6442000-10-09 18:26:42 +000030All the changes since the last beta release are bug fixes or changes
31to build support for specific platforms.
32
33Core language, builtins, and interpreter
34
35- A bug that caused crashes when __coerce__ was used with augmented
36 assignment, e.g. +=, was fixed.
37
38- Raise ZeroDivisionError when raising zero to a negative number,
39 e.g. 0.0 ** -2.0. Note that math.pow is unrelated to the builtin
40 power operator and the result of math.pow(0.0, -2.0) will vary by
41 platform. On Linux, it raises a ValueError.
42
43- A bug in Unicode string interpolation was fixed that occasionally
44 caused errors with formats including "%%". For example, the
45 following expression "%% %s" % u"abc" no longer raises a TypeError.
46
47- Compilation of deeply nested expressions raises MemoryError instead
48 of SyntaxError, e.g. eval("[" * 50 + "]" * 50).
49
50- In 2.0b2 on Windows, the interpreter wrote .pyc files in text mode,
51 rendering them useless. They are now written in binary mode again.
52
53Standard library
54
55- Keyword arguments are now accepted for most pattern and match object
56 methods in SRE, the standard regular expression engine.
57
58- In SRE, fix error with negative lookahead and lookbehind that
Jeremy Hylton32e20ff2000-10-09 19:48:11 +000059 manifested itself as a runtime error in patterns like "(?<!abc)(def)".
Jeremy Hyltoned9e6442000-10-09 18:26:42 +000060
61- Tkinter now supports Unicode strings and will set a Python exception
62 when an error occurs handling a specific Unicode string.
63
64- Fix memory management errors in Merge() and Tkapp_Call() routines.
65
66- Several changes were made to cStringIO to make it compatible with
67 the file-like object interface and with StringIO. If operations are
68 performed on a closed object, an exception is raised. The truncate
69 method now accepts a position argument and readline accepts a size
70 argument.
71
72- There were many changes made to the linuxaudiodev module and its
73 test suite; as a result, a short, unexpected audio sample should now
74 play when the regression test is run.
75
76 Note that this module is named poorly, because it should work
77 correctly on any platform that supports the Open Sound System
78 (OSS).
79
80 The module now raises exceptions when errors occur instead of
81 crashing. It also defines the AFMT_A_LAW format (logarithmic A-law
82 audio) and defines a getptr() method that calls the
83 SNDCTL_DSP_GETxPTR ioctl defined in the OSS Programmer's Guide.
84
85- The library_version attribute, introduced in an earlier beta, was
86 removed because it can not be supported with early versions of the C
87 readline library, which provides no way to determine the version at
88 compile-time.
89
90- The binascii module is now enabled on Win64.
91
Tim Peters46446d62000-10-09 21:19:31 +000092- tokenize.py no longer suffers "recursion depth" errors when parsing
93 programs with very long string literals.
94
Jeremy Hyltoned9e6442000-10-09 18:26:42 +000095Internals
96
97- Fix several buffer overflow vulnerabilities in calculate_path(),
98 which is called when the interpreter starts up to determine where
99 the standard library is installed. These vulnerabilities affect all
100 previous versions of Python and can be exploited by setting very
101 long values for PYTHONHOME or argv[0]. The risk is greatest for a
102 setuid Python script, although use of the wrapper in
103 Misc/setuid-prog.c will eliminate the vulnerability.
104
105- Fixed garbage collection bugs in instance creation that were
106 triggered when errors occurred during initialization. The solution,
107 applied in cPickle and in PyInstance_New(), is to call
108 PyObject_GC_Init() after the initialization of the object's
109 container attributes is complete.
110
111- pyexpat adds definitions of PyModule_AddStringConstant and
112 PyModule_AddObject if the Python version is less than 2.0, which
113 provides compatibility with PyXML on Python 1.5.2.
114
115- If the platform has a bogus definition for LONG_BIT (the number of
116 bits in a long), an error will be reported at compile time.
117
118- Fix bugs in _PyTuple_Resize() which caused hard-to-interpret garbage
119 collection crashes and possibly other, unreported crashes.
120
121- Fixed a memory leak in _PyUnicode_Fini().
122
123Build issues
124
125- configure now accepts a --with-suffix option that specifies the
126 executable. This is useful for builds on Cygwin and Mac OS X, for
127 example.
128
129- The mmap.PAGESIZE constant is now initialized using sysconf when
130 possible, which eliminates a dependency on -lucb for Reliant UNIX.
131
132- The md5 file should now compile on all platforms.
133
134- The select module now compiles on platforms that do not define
135 POLLRDNORM and related constants.
136
137- Darwin (Mac OS X): Initial support for static builds on this
138 platform.
139
Jeremy Hylton10921202000-10-09 18:34:12 +0000140- BeOS: A number of changes were made to the build and installation
141 process. ar-fake now operates on a directory of object files.
142 dl_export.h is gone, and its macros now appear on the mwcc command
143 line during build on PPC BeOS.
144
145 Platform directory in lib/python2.0 is "plat-beos5" (or
146 "plat-beos4", if building on BeOS 4.5), rather than "plat-beos".
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000147
148- Cygwin: Support for shared libraries, Tkinter, and sockets.
149
150- SunOS 4.1.4_JL: Fix test for directory existence in configure.
151
152Tools and other miscellany
153
154- Removed debugging prints from main used with freeze.
155
Tim Peters46446d62000-10-09 21:19:31 +0000156- IDLE auto-indent no longer crashes when it encounters Unicode
157 characters.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000158
159What's new in 2.0 beta 2 (since beta 1)?
160========================================
161
162Core language, builtins, and interpreter
163
Tim Peters482c0212000-09-26 06:33:09 +0000164- Add support for unbounded ints in %d,i,u,x,X,o formats; for example
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000165 "%d" % 2L**64 == "18446744073709551616".
Jeremy Hylton1b618592000-09-26 05:32:36 +0000166
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000167- Add -h and -V command line options to print the usage message and
168 Python version number and exit immediately.
169
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000170- eval() and exec accept Unicode objects as code parameters.
171
172- getattr() and setattr() now also accept Unicode objects for the
173 attribute name, which are converted to strings using the default
174 encoding before lookup.
175
176- Multiplication on string and Unicode now does proper bounds
177 checking; e.g. 'a' * 65536 * 65536 will raise ValueError, "repeated
178 string is too long."
179
180- Better error message when continue is found in try statement in a
181 loop.
182
Jeremy Hylton1b618592000-09-26 05:32:36 +0000183
184Standard library and extensions
185
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000186- array: reverse() method of array now works. buffer_info() now does
Jeremy Hylton1b618592000-09-26 05:32:36 +0000187 argument checking; it still takes no arguments.
188
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000189- asyncore/asynchat: Included most recent version from Sam Rushing.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000190
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000191- cgi: Accept '&' or ';' as separator characters when parsing form data.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000192
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000193- CGIHTTPServer: Now works on Windows (and perhaps even Mac).
Jeremy Hylton1b618592000-09-26 05:32:36 +0000194
195- ConfigParser: When reading the file, options spelled in upper case
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000196 letters are now correctly converted to lowercase.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000197
198- copy: Copy Unicode objects atomically.
199
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000200- cPickle: Fail gracefully when copy_reg can't be imported.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000201
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000202- cStringIO: Implemented readlines() method.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000203
Fred Drake67233bc2000-09-26 16:40:27 +0000204- dbm: Add get() and setdefault() methods to dbm object. Add constant
205 `library' to module that names the library used. Added doc strings
206 and method names to error messages. Uses configure to determine
207 which ndbm.h file to include; Berkeley DB's nbdm and GDBM's ndbm is
208 now available options.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000209
210- distutils: Update to version 0.9.3.
211
212- dl: Add several dl.RTLD_ constants.
213
214- fpectl: Now supported on FreeBSD.
215
216- gc: Add DEBUG_SAVEALL option. When enabled all garbage objects
217 found by the collector will be saved in gc.garbage. This is useful
218 for debugging a program that creates reference cycles.
219
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000220- httplib: Three changes: Restore support for set_debuglevel feature
Jeremy Hylton1b618592000-09-26 05:32:36 +0000221 of HTTP class. Do not close socket on zero-length response. Do not
222 crash when server sends invalid content-length header.
223
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000224- mailbox: Mailbox class conforms better to qmail specifications.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000225
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000226- marshal: When reading a short, sign-extend on platforms where shorts
227 are bigger than 16 bits. When reading a long, repair the unportable
228 sign extension that was being done for 64-bit machines. (It assumed
229 that signed right shift sign-extends.)
230
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000231- operator: Add contains(), invert(), __invert__() as aliases for
232 __contains__(), inv(), and __inv__() respectively.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000233
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000234- os: Add support for popen2() and popen3() on all platforms where
235 fork() exists. (popen4() is still in the works.)
Jeremy Hylton1b618592000-09-26 05:32:36 +0000236
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000237- os: (Windows only:) Add startfile() function that acts like double-
Tim Peters482c0212000-09-26 06:33:09 +0000238 clicking on a file in Explorer (or passing the file name to the
239 DOS "start" command).
Jeremy Hylton1b618592000-09-26 05:32:36 +0000240
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000241- os.path: (Windows, DOS:) Treat trailing colon correctly in
Tim Peters482c0212000-09-26 06:33:09 +0000242 os.path.join. os.path.join("a:", "b") yields "a:b".
Jeremy Hylton1b618592000-09-26 05:32:36 +0000243
244- pickle: Now raises ValueError when an invalid pickle that contains
245 a non-string repr where a string repr was expected. This behavior
246 matches cPickle.
247
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000248- posixfile: Remove broken __del__() method.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000249
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000250- py_compile: support CR+LF line terminators in source file.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000251
252- readline: Does not immediately exit when ^C is hit when readline and
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000253 threads are configured. Adds definition of rl_library_version. (The
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000254 latter addition requires GNU readline 2.2 or later.)
Jeremy Hylton1b618592000-09-26 05:32:36 +0000255
256- rfc822: Domain literals returned by AddrlistClass method
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000257 getdomainliteral() are now properly wrapped in brackets.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000258
259- site: sys.setdefaultencoding() should only be called in case the
Tim Peters482c0212000-09-26 06:33:09 +0000260 standard default encoding ("ascii") is changed. This saves quite a
Jeremy Hylton1b618592000-09-26 05:32:36 +0000261 few cycles during startup since the first call to
262 setdefaultencoding() will initialize the codec registry and the
263 encodings package.
264
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000265- socket: Support for size hint in readlines() method of object returned
266 by makefile().
Jeremy Hylton1b618592000-09-26 05:32:36 +0000267
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000268- sre: Added experimental expand() method to match objects. Does not
Jeremy Hylton625915e2000-10-02 13:43:33 +0000269 use buffer interface on Unicode strings. Does not hang if group id
Jeremy Hylton1b618592000-09-26 05:32:36 +0000270 is followed by whitespace.
271
Fred Drake64bb3802000-09-26 16:21:35 +0000272- StringIO: Size hint in readlines() is now supported as documented.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000273
274- struct: Check ranges for bytes and shorts.
275
276- urllib: Improved handling of win32 proxy settings. Fixed quote and
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000277 quote_plus functions so that the always encode a comma.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000278
279- Tkinter: Image objects are now guaranteed to have unique ids. Set
280 event.delta to zero if Tk version doesn't support mousewheel.
281 Removed some debugging prints.
282
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000283- UserList: now implements __contains__().
Jeremy Hylton1b618592000-09-26 05:32:36 +0000284
Fred Drake67233bc2000-09-26 16:40:27 +0000285- webbrowser: On Windows, use os.startfile() instead of os.popen(),
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000286 which works around a bug in Norton AntiVirus 2000 that leads directly
287 to a Blue Screen freeze.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000288
289- xml: New version detection code allows PyXML to override standard
290 XML package if PyXML version is greater than 0.6.1.
291
Fred Drake64bb3802000-09-26 16:21:35 +0000292- xml.dom: DOM level 1 support for basic XML. Includes xml.dom.minidom
293 (conventional DOM), and xml.dom.pulldom, which allows building the DOM
294 tree only for nodes which are sufficiently interesting to a specific
295 application. Does not provide the HTML-specific extensions. Still
296 undocumented.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000297
Fred Drake64bb3802000-09-26 16:21:35 +0000298- xml.sax: SAX 2 support for Python, including all the handler
299 interfaces needed to process XML 1.0 compliant XML. Some
300 documentation is already available.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000301
Fred Drake64bb3802000-09-26 16:21:35 +0000302- pyexpat: Renamed to xml.parsers.expat since this is part of the new,
303 packagized XML support.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000304
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000305
Jeremy Hylton1b618592000-09-26 05:32:36 +0000306C API
307
308- Add three new convenience functions for module initialization --
309 PyModule_AddObject(), PyModule_AddIntConstant(), and
310 PyModule_AddStringConstant().
311
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000312- Cleaned up definition of NULL in C source code; all definitions were
Jeremy Hylton1b618592000-09-26 05:32:36 +0000313 removed and add #error to Python.h if NULL isn't defined after
314 #include of stdio.h.
315
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000316- Py_PROTO() macros that were removed in 2.0b1 have been restored for
Jeremy Hylton1b618592000-09-26 05:32:36 +0000317 backwards compatibility (at the source level) with old extensions.
318
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000319- A wrapper API was added for signal() and sigaction(). Instead of
320 either function, always use PyOS_getsig() to get a signal handler
321 and PyOS_setsig() to set one. A new convenience typedef
322 PyOS_sighandler_t is defined for the type of signal handlers.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000323
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000324- Add PyString_AsStringAndSize() function that provides access to the
Jeremy Hylton1b618592000-09-26 05:32:36 +0000325 internal data buffer and size of a string object -- or the default
326 encoded version of a Unicode object.
327
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000328- PyString_Size() and PyString_AsString() accept Unicode objects.
329
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000330- The standard header <limits.h> is now included by Python.h (if it
Fred Drake64bb3802000-09-26 16:21:35 +0000331 exists). INT_MAX and LONG_MAX will always be defined, even if
332 <limits.h> is not available.
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000333
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000334- PyFloat_FromString takes a second argument, pend, that was
335 effectively useless. It is now officially useless but preserved for
336 backwards compatibility. If the pend argument is not NULL, *pend is
337 set to NULL.
338
339- PyObject_GetAttr() and PyObject_SetAttr() now accept Unicode objects
340 for the attribute name. See note on getattr() above.
341
342- A few bug fixes to argument processing for Unicode.
343 PyArg_ParseTupleAndKeywords() now accepts "es#" and "es".
344 PyArg_Parse() special cases "s#" for Unicode objects; it returns a
345 pointer to the default encoded string data instead of to the raw
346 UTF-16.
347
348- Py_BuildValue accepts B format (for bgen-generated code).
349
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000350
Jeremy Hylton1b618592000-09-26 05:32:36 +0000351Internals
352
353- On Unix, fix code for finding Python installation directory so that
354 it works when argv[0] is a relative path.
355
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000356- Added a true tnicode_internal_encode() function and fixed the
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000357 unicode_internal_decode function() to support Unicode objects directly
Jeremy Hylton1b618592000-09-26 05:32:36 +0000358 rather than by generating a copy of the object.
359
Tim Peters482c0212000-09-26 06:33:09 +0000360- Several of the internal Unicode tables are much smaller now, and
361 the source code should be much friendlier to weaker compilers.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000362
Jeremy Hylton97693b02000-09-26 17:42:51 +0000363- In the garbage collector: Fixed bug in collection of tuples. Fixed
364 bug that caused some instances to be removed from the container set
365 while they were still live. Fixed parsing in gc.set_debug() for
366 platforms where sizeof(long) > sizeof(int).
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000367
368- Fixed refcount problem in instance deallocation that only occurred
369 when Py_REF_DEBUG was defined and Py_TRACE_REFS was not.
370
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000371- On Windows, getpythonregpath is now protected against null data in
372 registry key.
373
374- On Unix, create .pyc/.pyo files with O_EXCL flag to avoid a race
375 condition.
376
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000377
Jeremy Hylton1b618592000-09-26 05:32:36 +0000378Build and platform-specific issues
379
380- Better support of GNU Pth via --with-pth configure option.
381
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000382- Python/C API now properly exposed to dynamically-loaded extension
383 modules on Reliant UNIX.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000384
385- Changes for the benefit of SunOS 4.1.4 (really!). mmapmodule.c:
386 Don't define MS_SYNC to be zero when it is undefined. Added missing
387 prototypes in posixmodule.c.
388
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000389- Improved support for HP-UX build. Threads should now be correctly
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000390 configured (on HP-UX 10.20 and 11.00).
Jeremy Hylton1b618592000-09-26 05:32:36 +0000391
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000392- Fix largefile support on older NetBSD systems and OpenBSD by adding
393 define for TELL64.
394
395
396Tools and other miscellany
397
398- ftpmirror: Call to main() is wrapped in if __name__ == "__main__".
399
400- freeze: The modulefinder now works with 2.0 opcodes.
401
402- IDLE:
403 Move hackery of sys.argv until after the Tk instance has been
404 created, which allows the application-specific Tkinter
405 initialization to be executed if present; also pass an explicit
406 className parameter to the Tk() constructor.
Fred Drake64bb3802000-09-26 16:21:35 +0000407
Jeremy Hylton1b618592000-09-26 05:32:36 +0000408
409What's new in 2.0 beta 1?
410=========================
411
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000412Source Incompatibilities
413------------------------
414
415None. Note that 1.6 introduced several incompatibilities with 1.5.2,
416such as single-argument append(), connect() and bind(), and changes to
417str(long) and repr(float).
418
419
420Binary Incompatibilities
421------------------------
422
423- Third party extensions built for Python 1.5.x or 1.6 cannot be used
424with Python 2.0; these extensions will have to be rebuilt for Python
4252.0.
426
427- On Windows, attempting to import a third party extension built for
428Python 1.5.x or 1.6 results in an immediate crash; there's not much we
429can do about this. Check your PYTHONPATH environment variable!
430
431- Python bytecode files (*.pyc and *.pyo) are not compatible between
432releases.
433
434
435Overview of Changes Since 1.6
436-----------------------------
437
438There are many new modules (including brand new XML support through
439the xml package, and i18n support through the gettext module); a list
440of all new modules is included below. Lots of bugs have been fixed.
441
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000442The process for making major new changes to the language has changed
443since Python 1.6. Enhancements must now be documented by a Python
444Enhancement Proposal (PEP) before they can be accepted.
445
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000446There are several important syntax enhancements, described in more
447detail below:
448
449 - Augmented assignment, e.g. x += 1
450
451 - List comprehensions, e.g. [x**2 for x in range(10)]
452
453 - Extended import statement, e.g. import Module as Name
454
455 - Extended print statement, e.g. print >> file, "Hello"
456
457Other important changes:
458
459 - Optional collection of cyclical garbage
460
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000461Python Enhancement Proposal (PEP)
462---------------------------------
463
464PEP stands for Python Enhancement Proposal. A PEP is a design
465document providing information to the Python community, or describing
466a new feature for Python. The PEP should provide a concise technical
467specification of the feature and a rationale for the feature.
468
469We intend PEPs to be the primary mechanisms for proposing new
470features, for collecting community input on an issue, and for
471documenting the design decisions that have gone into Python. The PEP
472author is responsible for building consensus within the community and
473documenting dissenting opinions.
474
475The PEPs are available at http://python.sourceforge.net/peps/.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000476
477Augmented Assignment
478--------------------
479
480This must have been the most-requested feature of the past years!
481Eleven new assignment operators were added:
482
Guido van Rossume905e952000-09-05 12:42:46 +0000483 += -= *= /= %= **= <<= >>= &= ^= |=
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000484
485For example,
486
487 A += B
488
489is similar to
490
491 A = A + B
492
493except that A is evaluated only once (relevant when A is something
494like dict[index].attr).
495
496However, if A is a mutable object, A may be modified in place. Thus,
497if A is a number or a string, A += B has the same effect as A = A+B
498(except A is only evaluated once); but if a is a list, A += B has the
499same effect as A.extend(B)!
500
501Classes and built-in object types can override the new operators in
502order to implement the in-place behavior; the not-in-place behavior is
503used automatically as a fallback when an object doesn't implement the
504in-place behavior. For classes, the method name is derived from the
505method name for the corresponding not-in-place operator by inserting
506an 'i' in front of the name, e.g. __iadd__ implements in-place
507__add__.
508
509Augmented assignment was implemented by Thomas Wouters.
510
511
512List Comprehensions
513-------------------
514
515This is a flexible new notation for lists whose elements are computed
516from another list (or lists). The simplest form is:
517
518 [<expression> for <variable> in <sequence>]
519
Guido van Rossum56db0952000-09-06 23:34:25 +0000520For example, [i**2 for i in range(4)] yields the list [0, 1, 4, 9].
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000521This is more efficient than a for loop with a list.append() call.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000522
523You can also add a condition:
524
525 [<expression> for <variable> in <sequence> if <condition>]
526
527For example, [w for w in words if w == w.lower()] would yield the list
528of words that contain no uppercase characters. This is more efficient
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000529than a for loop with an if statement and a list.append() call.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000530
531You can also have nested for loops and more than one 'if' clause. For
532example, here's a function that flattens a sequence of sequences::
533
534 def flatten(seq):
535 return [x for subseq in seq for x in subseq]
536
537 flatten([[0], [1,2,3], [4,5], [6,7,8,9], []])
538
539This prints
540
541 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
542
543List comprehensions originated as a patch set from Greg Ewing; Skip
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000544Montanaro and Thomas Wouters also contributed. Described by PEP 202.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000545
546
547Extended Import Statement
548-------------------------
549
550Many people have asked for a way to import a module under a different
551name. This can be accomplished like this:
552
553 import foo
554 bar = foo
555 del foo
556
557but this common idiom gets old quickly. A simple extension of the
558import statement now allows this to be written as follows:
559
560 import foo as bar
561
562There's also a variant for 'from ... import':
563
564 from foo import bar as spam
565
566This also works with packages; e.g. you can write this:
567
568 import test.regrtest as regrtest
569
570Note that 'as' is not a new keyword -- it is recognized only in this
571context (this is only possible because the syntax for the import
572statement doesn't involve expressions).
573
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000574Implemented by Thomas Wouters. Described by PEP 221.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000575
576
577Extended Print Statement
578------------------------
579
580Easily the most controversial new feature, this extension to the print
581statement adds an option to make the output go to a different file
582than the default sys.stdout.
583
584For example, to write an error message to sys.stderr, you can now
585write:
586
587 print >> sys.stderr, "Error: bad dog!"
588
589As a special feature, if the expression used to indicate the file
Fred Drake45888ff2000-09-29 17:09:11 +0000590evaluates to None, the current value of sys.stdout is used. Thus:
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000591
592 print >> None, "Hello world"
593
594is equivalent to
595
596 print "Hello world"
597
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000598Design and implementation by Barry Warsaw. Described by PEP 214.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000599
600
601Optional Collection of Cyclical Garbage
602---------------------------------------
603
604Python is now equipped with a garbage collector that can hunt down
605cyclical references between Python objects. It's no replacement for
606reference counting; in fact, it depends on the reference counts being
607correct, and decides that a set of objects belong to a cycle if all
608their reference counts can be accounted for from their references to
609each other. This devious scheme was first proposed by Eric Tiedemann,
610and brought to implementation by Neil Schemenauer.
611
612There's a module "gc" that lets you control some parameters of the
613garbage collection. There's also an option to the configure script
614that lets you enable or disable the garbage collection. In 2.0b1,
615it's on by default, so that we (hopefully) can collect decent user
616experience with this new feature. There are some questions about its
Fred Drake9f11cf82000-09-29 17:54:40 +0000617performance. If it proves to be too much of a problem, we'll turn it
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000618off by default in the final 2.0 release.
619
620
621Smaller Changes
622---------------
623
624A new function zip() was added. zip(seq1, seq2, ...) is equivalent to
625map(None, seq1, seq2, ...) when the sequences have the same length;
626i.e. zip([1,2,3], [10,20,30]) returns [(1,10), (2,20), (3,30)]. When
627the lists are not all the same length, the shortest list wins:
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000628zip([1,2,3], [10,20]) returns [(1,10), (2,20)]. See PEP 201.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000629
630sys.version_info is a tuple (major, minor, micro, level, serial).
631
632Dictionaries have an odd new method, setdefault(key, default).
633dict.setdefault(key, default) returns dict[key] if it exists; if not,
634it sets dict[key] to default and returns that value. Thus:
635
636 dict.setdefault(key, []).append(item)
637
638does the same work as this common idiom:
639
640 if not dict.has_key(key):
641 dict[key] = []
642 dict[key].append(item)
643
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000644There are two new variants of SyntaxError that are raised for
645indentation-related errors: IndentationError and TabError.
646
647Changed \x to consume exactly two hex digits; see PEP 223. Added \U
648escape that consumes exactly eight hex digits.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000649
650The limits on the size of expressions and file in Python source code
651have been raised from 2**16 to 2**32. Previous versions of Python
652were limited because the maximum argument size the Python VM accepted
653was 2**16. This limited the size of object constructor expressions,
654e.g. [1,2,3] or {'a':1, 'b':2}, and the size of source files. This
655limit was raised thanks to a patch by Charles Waldman that effectively
656fixes the problem. It is now much more likely that you will be
657limited by available memory than by an arbitrary limit in Python.
658
659The interpreter's maximum recursion depth can be modified by Python
660programs using sys.getrecursionlimit and sys.setrecursionlimit. This
661limit is the maximum number of recursive calls that can be made by
662Python code. The limit exists to prevent infinite recursion from
663overflowing the C stack and causing a core dump. The default value is
6641000. The maximum safe value for a particular platform can be found
665by running Misc/find_recursionlimit.py.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000666
667New Modules and Packages
668------------------------
669
670atexit - for registering functions to be called when Python exits.
671
672imputil - Greg Stein's alternative API for writing custom import
673hooks.
674
675pyexpat - an interface to the Expat XML parser, contributed by Paul
676Prescod.
677
678xml - a new package with XML support code organized (so far) in three
679subpackages: xml.dom, xml.sax, and xml.parsers. Describing these
680would fill a volume. There's a special feature whereby a
681user-installed package named _xmlplus overrides the standard
682xmlpackage; this is intended to give the XML SIG a hook to distribute
683backwards-compatible updates to the standard xml package.
684
685webbrowser - a platform-independent API to launch a web browser.
686
687
Guido van Rossume905e952000-09-05 12:42:46 +0000688Changed Modules
689---------------
690
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000691array -- new methods for array objects: count, extend, index, pop, and
692remove
693
694binascii -- new functions b2a_hex and a2b_hex that convert between
695binary data and its hex representation
696
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000697calendar -- Many new functions that support features including control
698over which day of the week is the first day, returning strings instead
699of printing them. Also new symbolic constants for days of week,
700e.g. MONDAY, ..., SUNDAY.
701
702cgi -- FieldStorage objects have a getvalue method that works like a
703dictionary's get method and returns the value attribute of the object.
704
705ConfigParser -- The parser object has new methods has_option,
706remove_section, remove_option, set, and write. They allow the module
707to be used for writing config files as well as reading them.
708
709ftplib -- ntransfercmd(), transfercmd(), and retrbinary() all now
Guido van Rossume905e952000-09-05 12:42:46 +0000710optionally support the RFC 959 REST command.
711
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000712gzip -- readline and readlines now accept optional size arguments
Guido van Rossume905e952000-09-05 12:42:46 +0000713
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000714httplib -- New interfaces and support for HTTP/1.1 by Greg Stein. See
715the module doc strings for details.
Guido van Rossum830ca2a2000-09-05 15:34:16 +0000716
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000717locale -- implement getdefaultlocale for Win32 and Macintosh
718
719marshal -- no longer dumps core when marshaling deeply nested or
720recursive data structures
721
722os -- new functions isatty, seteuid, setegid, setreuid, setregid
723
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000724os/popen2 -- popen2/popen3/popen4 support under Windows. popen2/popen3
725support under Unix.
726
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000727os/pty -- support for openpty and forkpty
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000728
729os.path -- fix semantics of os.path.commonprefix
730
731smtplib -- support for sending very long messages
732
733socket -- new function getfqdn()
734
735readline -- new functions to read, write and truncate history files.
736The readline section of the library reference manual contains an
737example.
738
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000739select -- add interface to poll system call
740
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000741shutil -- new copyfileobj function
742
743SimpleHTTPServer, CGIHTTPServer -- Fix problems with buffering in the
744HTTP server.
745
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000746Tkinter -- optimization of function flatten
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000747
748urllib -- scans environment variables for proxy configuration,
Tim Peters8b092332000-09-05 20:15:25 +0000749e.g. http_proxy.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000750
751whichdb -- recognizes dumbdbm format
Guido van Rossume905e952000-09-05 12:42:46 +0000752
753
754Obsolete Modules
755----------------
756
757None. However note that 1.6 made a whole slew of modules obsolete:
758stdwin, soundex, cml, cmpcache, dircache, dump, find, grep, packmail,
759poly, zmod, strop, util, whatsound.
760
761
762Changed, New, Obsolete Tools
763----------------------------
764
Tim Peters8b092332000-09-05 20:15:25 +0000765None.
Guido van Rossume905e952000-09-05 12:42:46 +0000766
767
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000768C-level Changes
769---------------
770
771Several cleanup jobs were carried out throughout the source code.
772
773All C code was converted to ANSI C; we got rid of all uses of the
774Py_PROTO() macro, which makes the header files a lot more readable.
775
776Most of the portability hacks were moved to a new header file,
777pyport.h; several other new header files were added and some old
778header files were removed, in an attempt to create a more rational set
779of header files. (Few of these ever need to be included explicitly;
780they are all included by Python.h.)
781
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000782Trent Mick ensured portability to 64-bit platforms, under both Linux
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000783and Win64, especially for the new Intel Itanium processor. Mick also
784added large file support for Linux64 and Win64.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000785
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000786The C APIs to return an object's size have been update to consistently
787use the form PyXXX_Size, e.g. PySequence_Size and PyDict_Size. In
788previous versions, the abstract interfaces used PyXXX_Length and the
789concrete interfaces used PyXXX_Size. The old names,
790e.g. PyObject_Length, are still available for backwards compatibility
791at the API level, but are deprecated.
792
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000793The PyOS_CheckStack function has been implemented on Windows by
794Fredrik Lundh. It prevents Python from failing with a stack overflow
795on Windows.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000796
797The GC changes resulted in creation of two new slots on object,
798tp_traverse and tp_clear. The augmented assignment changes result in
Guido van Rossum4338a282000-09-06 13:02:08 +0000799the creation of a new slot for each in-place operator.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000800
801The GC API creates new requirements for container types implemented in
Guido van Rossum4338a282000-09-06 13:02:08 +0000802C extension modules. See Include/objimpl.h for details.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000803
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000804PyErr_Format has been updated to automatically calculate the size of
805the buffer needed to hold the formatted result string. This change
806prevents crashes caused by programmer error.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000807
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000808New C API calls: PyObject_AsFileDescriptor, PyErr_WriteUnraisable.
Guido van Rossume905e952000-09-05 12:42:46 +0000809
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000810PyRun_AnyFileEx, PyRun_SimpleFileEx, PyRun_FileEx -- New functions
811that are the same as their non-Ex counterparts except they take an
812extra flag argument that tells them to close the file when done.
813
814XXX There were other API changes that should be fleshed out here.
Guido van Rossumab9d6f01998-08-10 22:01:13 +0000815
Tim Peters8b092332000-09-05 20:15:25 +0000816
817Windows Changes
818---------------
819
820New popen2/popen3/peopen4 in os module (see Changed Modules above).
821
822os.popen is much more usable on Windows 95 and 98. See Microsoft
823Knowledge Base article Q150956. The Win9x workaround described there
824is implemented by the new w9xpopen.exe helper in the root of your
825Python installation. Note that Python uses this internally; it is not
826a standalone program.
827
828Administrator privileges are no longer required to install Python
829on Windows NT or Windows 2000. If you have administrator privileges,
830Python's registry info will be written under HKEY_LOCAL_MACHINE.
831Otherwise the installer backs off to writing Python's registry info
Guido van Rossum4338a282000-09-06 13:02:08 +0000832under HKEY_CURRENT_USER. The latter is sufficient for all "normal"
Tim Peters8b092332000-09-05 20:15:25 +0000833uses of Python, but will prevent some advanced uses from working
834(for example, running a Python script as an NT service, or possibly
835from CGI).
836
837[This was new in 1.6] The installer no longer runs a separate Tcl/Tk
838installer; instead, it installs the needed Tcl/Tk files directly in the
839Python directory. If you already have a Tcl/Tk installation, this
840wastes some disk space (about 4 Megs) but avoids problems with
841conflicting Tcl/Tk installations, and makes it much easier for Python
842to ensure that Tcl/Tk can find all its files.
843
844[This was new in 1.6] The Windows installer now installs by default in
845\Python20\ on the default volume, instead of \Program Files\Python-2.0\.
846
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000847
848Updates to the changes between 1.5.2 and 1.6
849--------------------------------------------
850
851The 1.6 NEWS file can't be changed after the release is done, so here
852is some late-breaking news:
853
854New APIs in locale.py: normalize(), getdefaultlocale(), resetlocale(),
855and changes to getlocale() and setlocale().
856
857The new module is now enabled per default.
858
859It is not true that the encodings codecs cannot be used for normal
860strings: the string.encode() (which is also present on 8-bit strings
861!) allows using them for 8-bit strings too, e.g. to convert files from
862cp1252 (Windows) to latin-1 or vice-versa.
863
864Japanese codecs are available from Tamito KAJIYAMA:
865http://pseudo.grad.sccs.chukyo-u.ac.jp/~kajiyama/python/
866
867
Guido van Rossumab9d6f01998-08-10 22:01:13 +0000868======================================================================