blob: 2183e42be2d2578f9ec7a2a6d76880f69524d27c [file] [log] [blame]
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
20All the changes since the last beta release are bug fixes or changes
21to build support for specific platforms.
22
23Core language, builtins, and interpreter
24
25- A bug that caused crashes when __coerce__ was used with augmented
26 assignment, e.g. +=, was fixed.
27
28- Raise ZeroDivisionError when raising zero to a negative number,
29 e.g. 0.0 ** -2.0. Note that math.pow is unrelated to the builtin
30 power operator and the result of math.pow(0.0, -2.0) will vary by
31 platform. On Linux, it raises a ValueError.
32
33- A bug in Unicode string interpolation was fixed that occasionally
34 caused errors with formats including "%%". For example, the
35 following expression "%% %s" % u"abc" no longer raises a TypeError.
36
37- Compilation of deeply nested expressions raises MemoryError instead
38 of SyntaxError, e.g. eval("[" * 50 + "]" * 50).
39
40- In 2.0b2 on Windows, the interpreter wrote .pyc files in text mode,
41 rendering them useless. They are now written in binary mode again.
42
43Standard library
44
45- Keyword arguments are now accepted for most pattern and match object
46 methods in SRE, the standard regular expression engine.
47
48- In SRE, fix error with negative lookahead and lookbehind that
49 manifested itself as a runtime error in patterns like "?<!abc)(def)".
50
51- Tkinter now supports Unicode strings and will set a Python exception
52 when an error occurs handling a specific Unicode string.
53
54- Fix memory management errors in Merge() and Tkapp_Call() routines.
55
56- Several changes were made to cStringIO to make it compatible with
57 the file-like object interface and with StringIO. If operations are
58 performed on a closed object, an exception is raised. The truncate
59 method now accepts a position argument and readline accepts a size
60 argument.
61
62- There were many changes made to the linuxaudiodev module and its
63 test suite; as a result, a short, unexpected audio sample should now
64 play when the regression test is run.
65
66 Note that this module is named poorly, because it should work
67 correctly on any platform that supports the Open Sound System
68 (OSS).
69
70 The module now raises exceptions when errors occur instead of
71 crashing. It also defines the AFMT_A_LAW format (logarithmic A-law
72 audio) and defines a getptr() method that calls the
73 SNDCTL_DSP_GETxPTR ioctl defined in the OSS Programmer's Guide.
74
75- The library_version attribute, introduced in an earlier beta, was
76 removed because it can not be supported with early versions of the C
77 readline library, which provides no way to determine the version at
78 compile-time.
79
80- The binascii module is now enabled on Win64.
81
82Internals
83
84- Fix several buffer overflow vulnerabilities in calculate_path(),
85 which is called when the interpreter starts up to determine where
86 the standard library is installed. These vulnerabilities affect all
87 previous versions of Python and can be exploited by setting very
88 long values for PYTHONHOME or argv[0]. The risk is greatest for a
89 setuid Python script, although use of the wrapper in
90 Misc/setuid-prog.c will eliminate the vulnerability.
91
92- Fixed garbage collection bugs in instance creation that were
93 triggered when errors occurred during initialization. The solution,
94 applied in cPickle and in PyInstance_New(), is to call
95 PyObject_GC_Init() after the initialization of the object's
96 container attributes is complete.
97
98- pyexpat adds definitions of PyModule_AddStringConstant and
99 PyModule_AddObject if the Python version is less than 2.0, which
100 provides compatibility with PyXML on Python 1.5.2.
101
102- If the platform has a bogus definition for LONG_BIT (the number of
103 bits in a long), an error will be reported at compile time.
104
105- Fix bugs in _PyTuple_Resize() which caused hard-to-interpret garbage
106 collection crashes and possibly other, unreported crashes.
107
108- Fixed a memory leak in _PyUnicode_Fini().
109
110Build issues
111
112- configure now accepts a --with-suffix option that specifies the
113 executable. This is useful for builds on Cygwin and Mac OS X, for
114 example.
115
116- The mmap.PAGESIZE constant is now initialized using sysconf when
117 possible, which eliminates a dependency on -lucb for Reliant UNIX.
118
119- The md5 file should now compile on all platforms.
120
121- The select module now compiles on platforms that do not define
122 POLLRDNORM and related constants.
123
124- Darwin (Mac OS X): Initial support for static builds on this
125 platform.
126
127- BeOS: Many changes were made to support compilation on BeOS 4.5 and
128 5.0.
129
130- Cygwin: Support for shared libraries, Tkinter, and sockets.
131
132- SunOS 4.1.4_JL: Fix test for directory existence in configure.
133
134Tools and other miscellany
135
136- Removed debugging prints from main used with freeze.
137
138- IDLE auto-indent internals no longer crashes when it encounters
139 Unicode characters in the range 128 to 255.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000140
141What's new in 2.0 beta 2 (since beta 1)?
142========================================
143
144Core language, builtins, and interpreter
145
Tim Peters482c0212000-09-26 06:33:09 +0000146- Add support for unbounded ints in %d,i,u,x,X,o formats; for example
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000147 "%d" % 2L**64 == "18446744073709551616".
Jeremy Hylton1b618592000-09-26 05:32:36 +0000148
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000149- Add -h and -V command line options to print the usage message and
150 Python version number and exit immediately.
151
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000152- eval() and exec accept Unicode objects as code parameters.
153
154- getattr() and setattr() now also accept Unicode objects for the
155 attribute name, which are converted to strings using the default
156 encoding before lookup.
157
158- Multiplication on string and Unicode now does proper bounds
159 checking; e.g. 'a' * 65536 * 65536 will raise ValueError, "repeated
160 string is too long."
161
162- Better error message when continue is found in try statement in a
163 loop.
164
Jeremy Hylton1b618592000-09-26 05:32:36 +0000165
166Standard library and extensions
167
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000168- array: reverse() method of array now works. buffer_info() now does
Jeremy Hylton1b618592000-09-26 05:32:36 +0000169 argument checking; it still takes no arguments.
170
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000171- asyncore/asynchat: Included most recent version from Sam Rushing.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000172
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000173- cgi: Accept '&' or ';' as separator characters when parsing form data.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000174
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000175- CGIHTTPServer: Now works on Windows (and perhaps even Mac).
Jeremy Hylton1b618592000-09-26 05:32:36 +0000176
177- ConfigParser: When reading the file, options spelled in upper case
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000178 letters are now correctly converted to lowercase.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000179
180- copy: Copy Unicode objects atomically.
181
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000182- cPickle: Fail gracefully when copy_reg can't be imported.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000183
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000184- cStringIO: Implemented readlines() method.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000185
Fred Drake67233bc2000-09-26 16:40:27 +0000186- dbm: Add get() and setdefault() methods to dbm object. Add constant
187 `library' to module that names the library used. Added doc strings
188 and method names to error messages. Uses configure to determine
189 which ndbm.h file to include; Berkeley DB's nbdm and GDBM's ndbm is
190 now available options.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000191
192- distutils: Update to version 0.9.3.
193
194- dl: Add several dl.RTLD_ constants.
195
196- fpectl: Now supported on FreeBSD.
197
198- gc: Add DEBUG_SAVEALL option. When enabled all garbage objects
199 found by the collector will be saved in gc.garbage. This is useful
200 for debugging a program that creates reference cycles.
201
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000202- httplib: Three changes: Restore support for set_debuglevel feature
Jeremy Hylton1b618592000-09-26 05:32:36 +0000203 of HTTP class. Do not close socket on zero-length response. Do not
204 crash when server sends invalid content-length header.
205
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000206- mailbox: Mailbox class conforms better to qmail specifications.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000207
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000208- marshal: When reading a short, sign-extend on platforms where shorts
209 are bigger than 16 bits. When reading a long, repair the unportable
210 sign extension that was being done for 64-bit machines. (It assumed
211 that signed right shift sign-extends.)
212
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000213- operator: Add contains(), invert(), __invert__() as aliases for
214 __contains__(), inv(), and __inv__() respectively.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000215
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000216- os: Add support for popen2() and popen3() on all platforms where
217 fork() exists. (popen4() is still in the works.)
Jeremy Hylton1b618592000-09-26 05:32:36 +0000218
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000219- os: (Windows only:) Add startfile() function that acts like double-
Tim Peters482c0212000-09-26 06:33:09 +0000220 clicking on a file in Explorer (or passing the file name to the
221 DOS "start" command).
Jeremy Hylton1b618592000-09-26 05:32:36 +0000222
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000223- os.path: (Windows, DOS:) Treat trailing colon correctly in
Tim Peters482c0212000-09-26 06:33:09 +0000224 os.path.join. os.path.join("a:", "b") yields "a:b".
Jeremy Hylton1b618592000-09-26 05:32:36 +0000225
226- pickle: Now raises ValueError when an invalid pickle that contains
227 a non-string repr where a string repr was expected. This behavior
228 matches cPickle.
229
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000230- posixfile: Remove broken __del__() method.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000231
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000232- py_compile: support CR+LF line terminators in source file.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000233
234- readline: Does not immediately exit when ^C is hit when readline and
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000235 threads are configured. Adds definition of rl_library_version. (The
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000236 latter addition requires GNU readline 2.2 or later.)
Jeremy Hylton1b618592000-09-26 05:32:36 +0000237
238- rfc822: Domain literals returned by AddrlistClass method
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000239 getdomainliteral() are now properly wrapped in brackets.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000240
241- site: sys.setdefaultencoding() should only be called in case the
Tim Peters482c0212000-09-26 06:33:09 +0000242 standard default encoding ("ascii") is changed. This saves quite a
Jeremy Hylton1b618592000-09-26 05:32:36 +0000243 few cycles during startup since the first call to
244 setdefaultencoding() will initialize the codec registry and the
245 encodings package.
246
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000247- socket: Support for size hint in readlines() method of object returned
248 by makefile().
Jeremy Hylton1b618592000-09-26 05:32:36 +0000249
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000250- sre: Added experimental expand() method to match objects. Does not
Jeremy Hylton625915e2000-10-02 13:43:33 +0000251 use buffer interface on Unicode strings. Does not hang if group id
Jeremy Hylton1b618592000-09-26 05:32:36 +0000252 is followed by whitespace.
253
Fred Drake64bb3802000-09-26 16:21:35 +0000254- StringIO: Size hint in readlines() is now supported as documented.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000255
256- struct: Check ranges for bytes and shorts.
257
258- urllib: Improved handling of win32 proxy settings. Fixed quote and
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000259 quote_plus functions so that the always encode a comma.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000260
261- Tkinter: Image objects are now guaranteed to have unique ids. Set
262 event.delta to zero if Tk version doesn't support mousewheel.
263 Removed some debugging prints.
264
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000265- UserList: now implements __contains__().
Jeremy Hylton1b618592000-09-26 05:32:36 +0000266
Fred Drake67233bc2000-09-26 16:40:27 +0000267- webbrowser: On Windows, use os.startfile() instead of os.popen(),
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000268 which works around a bug in Norton AntiVirus 2000 that leads directly
269 to a Blue Screen freeze.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000270
271- xml: New version detection code allows PyXML to override standard
272 XML package if PyXML version is greater than 0.6.1.
273
Fred Drake64bb3802000-09-26 16:21:35 +0000274- xml.dom: DOM level 1 support for basic XML. Includes xml.dom.minidom
275 (conventional DOM), and xml.dom.pulldom, which allows building the DOM
276 tree only for nodes which are sufficiently interesting to a specific
277 application. Does not provide the HTML-specific extensions. Still
278 undocumented.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000279
Fred Drake64bb3802000-09-26 16:21:35 +0000280- xml.sax: SAX 2 support for Python, including all the handler
281 interfaces needed to process XML 1.0 compliant XML. Some
282 documentation is already available.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000283
Fred Drake64bb3802000-09-26 16:21:35 +0000284- pyexpat: Renamed to xml.parsers.expat since this is part of the new,
285 packagized XML support.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000286
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000287
Jeremy Hylton1b618592000-09-26 05:32:36 +0000288C API
289
290- Add three new convenience functions for module initialization --
291 PyModule_AddObject(), PyModule_AddIntConstant(), and
292 PyModule_AddStringConstant().
293
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000294- Cleaned up definition of NULL in C source code; all definitions were
Jeremy Hylton1b618592000-09-26 05:32:36 +0000295 removed and add #error to Python.h if NULL isn't defined after
296 #include of stdio.h.
297
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000298- Py_PROTO() macros that were removed in 2.0b1 have been restored for
Jeremy Hylton1b618592000-09-26 05:32:36 +0000299 backwards compatibility (at the source level) with old extensions.
300
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000301- A wrapper API was added for signal() and sigaction(). Instead of
302 either function, always use PyOS_getsig() to get a signal handler
303 and PyOS_setsig() to set one. A new convenience typedef
304 PyOS_sighandler_t is defined for the type of signal handlers.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000305
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000306- Add PyString_AsStringAndSize() function that provides access to the
Jeremy Hylton1b618592000-09-26 05:32:36 +0000307 internal data buffer and size of a string object -- or the default
308 encoded version of a Unicode object.
309
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000310- PyString_Size() and PyString_AsString() accept Unicode objects.
311
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000312- The standard header <limits.h> is now included by Python.h (if it
Fred Drake64bb3802000-09-26 16:21:35 +0000313 exists). INT_MAX and LONG_MAX will always be defined, even if
314 <limits.h> is not available.
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000315
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000316- PyFloat_FromString takes a second argument, pend, that was
317 effectively useless. It is now officially useless but preserved for
318 backwards compatibility. If the pend argument is not NULL, *pend is
319 set to NULL.
320
321- PyObject_GetAttr() and PyObject_SetAttr() now accept Unicode objects
322 for the attribute name. See note on getattr() above.
323
324- A few bug fixes to argument processing for Unicode.
325 PyArg_ParseTupleAndKeywords() now accepts "es#" and "es".
326 PyArg_Parse() special cases "s#" for Unicode objects; it returns a
327 pointer to the default encoded string data instead of to the raw
328 UTF-16.
329
330- Py_BuildValue accepts B format (for bgen-generated code).
331
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000332
Jeremy Hylton1b618592000-09-26 05:32:36 +0000333Internals
334
335- On Unix, fix code for finding Python installation directory so that
336 it works when argv[0] is a relative path.
337
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000338- Added a true tnicode_internal_encode() function and fixed the
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000339 unicode_internal_decode function() to support Unicode objects directly
Jeremy Hylton1b618592000-09-26 05:32:36 +0000340 rather than by generating a copy of the object.
341
Tim Peters482c0212000-09-26 06:33:09 +0000342- Several of the internal Unicode tables are much smaller now, and
343 the source code should be much friendlier to weaker compilers.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000344
Jeremy Hylton97693b02000-09-26 17:42:51 +0000345- In the garbage collector: Fixed bug in collection of tuples. Fixed
346 bug that caused some instances to be removed from the container set
347 while they were still live. Fixed parsing in gc.set_debug() for
348 platforms where sizeof(long) > sizeof(int).
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000349
350- Fixed refcount problem in instance deallocation that only occurred
351 when Py_REF_DEBUG was defined and Py_TRACE_REFS was not.
352
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000353- On Windows, getpythonregpath is now protected against null data in
354 registry key.
355
356- On Unix, create .pyc/.pyo files with O_EXCL flag to avoid a race
357 condition.
358
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000359
Jeremy Hylton1b618592000-09-26 05:32:36 +0000360Build and platform-specific issues
361
362- Better support of GNU Pth via --with-pth configure option.
363
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000364- Python/C API now properly exposed to dynamically-loaded extension
365 modules on Reliant UNIX.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000366
367- Changes for the benefit of SunOS 4.1.4 (really!). mmapmodule.c:
368 Don't define MS_SYNC to be zero when it is undefined. Added missing
369 prototypes in posixmodule.c.
370
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000371- Improved support for HP-UX build. Threads should now be correctly
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000372 configured (on HP-UX 10.20 and 11.00).
Jeremy Hylton1b618592000-09-26 05:32:36 +0000373
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000374- Fix largefile support on older NetBSD systems and OpenBSD by adding
375 define for TELL64.
376
377
378Tools and other miscellany
379
380- ftpmirror: Call to main() is wrapped in if __name__ == "__main__".
381
382- freeze: The modulefinder now works with 2.0 opcodes.
383
384- IDLE:
385 Move hackery of sys.argv until after the Tk instance has been
386 created, which allows the application-specific Tkinter
387 initialization to be executed if present; also pass an explicit
388 className parameter to the Tk() constructor.
Fred Drake64bb3802000-09-26 16:21:35 +0000389
Jeremy Hylton1b618592000-09-26 05:32:36 +0000390
391What's new in 2.0 beta 1?
392=========================
393
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000394Source Incompatibilities
395------------------------
396
397None. Note that 1.6 introduced several incompatibilities with 1.5.2,
398such as single-argument append(), connect() and bind(), and changes to
399str(long) and repr(float).
400
401
402Binary Incompatibilities
403------------------------
404
405- Third party extensions built for Python 1.5.x or 1.6 cannot be used
406with Python 2.0; these extensions will have to be rebuilt for Python
4072.0.
408
409- On Windows, attempting to import a third party extension built for
410Python 1.5.x or 1.6 results in an immediate crash; there's not much we
411can do about this. Check your PYTHONPATH environment variable!
412
413- Python bytecode files (*.pyc and *.pyo) are not compatible between
414releases.
415
416
417Overview of Changes Since 1.6
418-----------------------------
419
420There are many new modules (including brand new XML support through
421the xml package, and i18n support through the gettext module); a list
422of all new modules is included below. Lots of bugs have been fixed.
423
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000424The process for making major new changes to the language has changed
425since Python 1.6. Enhancements must now be documented by a Python
426Enhancement Proposal (PEP) before they can be accepted.
427
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000428There are several important syntax enhancements, described in more
429detail below:
430
431 - Augmented assignment, e.g. x += 1
432
433 - List comprehensions, e.g. [x**2 for x in range(10)]
434
435 - Extended import statement, e.g. import Module as Name
436
437 - Extended print statement, e.g. print >> file, "Hello"
438
439Other important changes:
440
441 - Optional collection of cyclical garbage
442
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000443Python Enhancement Proposal (PEP)
444---------------------------------
445
446PEP stands for Python Enhancement Proposal. A PEP is a design
447document providing information to the Python community, or describing
448a new feature for Python. The PEP should provide a concise technical
449specification of the feature and a rationale for the feature.
450
451We intend PEPs to be the primary mechanisms for proposing new
452features, for collecting community input on an issue, and for
453documenting the design decisions that have gone into Python. The PEP
454author is responsible for building consensus within the community and
455documenting dissenting opinions.
456
457The PEPs are available at http://python.sourceforge.net/peps/.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000458
459Augmented Assignment
460--------------------
461
462This must have been the most-requested feature of the past years!
463Eleven new assignment operators were added:
464
Guido van Rossume905e952000-09-05 12:42:46 +0000465 += -= *= /= %= **= <<= >>= &= ^= |=
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000466
467For example,
468
469 A += B
470
471is similar to
472
473 A = A + B
474
475except that A is evaluated only once (relevant when A is something
476like dict[index].attr).
477
478However, if A is a mutable object, A may be modified in place. Thus,
479if A is a number or a string, A += B has the same effect as A = A+B
480(except A is only evaluated once); but if a is a list, A += B has the
481same effect as A.extend(B)!
482
483Classes and built-in object types can override the new operators in
484order to implement the in-place behavior; the not-in-place behavior is
485used automatically as a fallback when an object doesn't implement the
486in-place behavior. For classes, the method name is derived from the
487method name for the corresponding not-in-place operator by inserting
488an 'i' in front of the name, e.g. __iadd__ implements in-place
489__add__.
490
491Augmented assignment was implemented by Thomas Wouters.
492
493
494List Comprehensions
495-------------------
496
497This is a flexible new notation for lists whose elements are computed
498from another list (or lists). The simplest form is:
499
500 [<expression> for <variable> in <sequence>]
501
Guido van Rossum56db0952000-09-06 23:34:25 +0000502For example, [i**2 for i in range(4)] yields the list [0, 1, 4, 9].
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000503This is more efficient than a for loop with a list.append() call.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000504
505You can also add a condition:
506
507 [<expression> for <variable> in <sequence> if <condition>]
508
509For example, [w for w in words if w == w.lower()] would yield the list
510of words that contain no uppercase characters. This is more efficient
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000511than a for loop with an if statement and a list.append() call.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000512
513You can also have nested for loops and more than one 'if' clause. For
514example, here's a function that flattens a sequence of sequences::
515
516 def flatten(seq):
517 return [x for subseq in seq for x in subseq]
518
519 flatten([[0], [1,2,3], [4,5], [6,7,8,9], []])
520
521This prints
522
523 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
524
525List comprehensions originated as a patch set from Greg Ewing; Skip
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000526Montanaro and Thomas Wouters also contributed. Described by PEP 202.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000527
528
529Extended Import Statement
530-------------------------
531
532Many people have asked for a way to import a module under a different
533name. This can be accomplished like this:
534
535 import foo
536 bar = foo
537 del foo
538
539but this common idiom gets old quickly. A simple extension of the
540import statement now allows this to be written as follows:
541
542 import foo as bar
543
544There's also a variant for 'from ... import':
545
546 from foo import bar as spam
547
548This also works with packages; e.g. you can write this:
549
550 import test.regrtest as regrtest
551
552Note that 'as' is not a new keyword -- it is recognized only in this
553context (this is only possible because the syntax for the import
554statement doesn't involve expressions).
555
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000556Implemented by Thomas Wouters. Described by PEP 221.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000557
558
559Extended Print Statement
560------------------------
561
562Easily the most controversial new feature, this extension to the print
563statement adds an option to make the output go to a different file
564than the default sys.stdout.
565
566For example, to write an error message to sys.stderr, you can now
567write:
568
569 print >> sys.stderr, "Error: bad dog!"
570
571As a special feature, if the expression used to indicate the file
Fred Drake45888ff2000-09-29 17:09:11 +0000572evaluates to None, the current value of sys.stdout is used. Thus:
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000573
574 print >> None, "Hello world"
575
576is equivalent to
577
578 print "Hello world"
579
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000580Design and implementation by Barry Warsaw. Described by PEP 214.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000581
582
583Optional Collection of Cyclical Garbage
584---------------------------------------
585
586Python is now equipped with a garbage collector that can hunt down
587cyclical references between Python objects. It's no replacement for
588reference counting; in fact, it depends on the reference counts being
589correct, and decides that a set of objects belong to a cycle if all
590their reference counts can be accounted for from their references to
591each other. This devious scheme was first proposed by Eric Tiedemann,
592and brought to implementation by Neil Schemenauer.
593
594There's a module "gc" that lets you control some parameters of the
595garbage collection. There's also an option to the configure script
596that lets you enable or disable the garbage collection. In 2.0b1,
597it's on by default, so that we (hopefully) can collect decent user
598experience with this new feature. There are some questions about its
Fred Drake9f11cf82000-09-29 17:54:40 +0000599performance. If it proves to be too much of a problem, we'll turn it
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000600off by default in the final 2.0 release.
601
602
603Smaller Changes
604---------------
605
606A new function zip() was added. zip(seq1, seq2, ...) is equivalent to
607map(None, seq1, seq2, ...) when the sequences have the same length;
608i.e. zip([1,2,3], [10,20,30]) returns [(1,10), (2,20), (3,30)]. When
609the lists are not all the same length, the shortest list wins:
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000610zip([1,2,3], [10,20]) returns [(1,10), (2,20)]. See PEP 201.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000611
612sys.version_info is a tuple (major, minor, micro, level, serial).
613
614Dictionaries have an odd new method, setdefault(key, default).
615dict.setdefault(key, default) returns dict[key] if it exists; if not,
616it sets dict[key] to default and returns that value. Thus:
617
618 dict.setdefault(key, []).append(item)
619
620does the same work as this common idiom:
621
622 if not dict.has_key(key):
623 dict[key] = []
624 dict[key].append(item)
625
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000626There are two new variants of SyntaxError that are raised for
627indentation-related errors: IndentationError and TabError.
628
629Changed \x to consume exactly two hex digits; see PEP 223. Added \U
630escape that consumes exactly eight hex digits.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000631
632The limits on the size of expressions and file in Python source code
633have been raised from 2**16 to 2**32. Previous versions of Python
634were limited because the maximum argument size the Python VM accepted
635was 2**16. This limited the size of object constructor expressions,
636e.g. [1,2,3] or {'a':1, 'b':2}, and the size of source files. This
637limit was raised thanks to a patch by Charles Waldman that effectively
638fixes the problem. It is now much more likely that you will be
639limited by available memory than by an arbitrary limit in Python.
640
641The interpreter's maximum recursion depth can be modified by Python
642programs using sys.getrecursionlimit and sys.setrecursionlimit. This
643limit is the maximum number of recursive calls that can be made by
644Python code. The limit exists to prevent infinite recursion from
645overflowing the C stack and causing a core dump. The default value is
6461000. The maximum safe value for a particular platform can be found
647by running Misc/find_recursionlimit.py.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000648
649New Modules and Packages
650------------------------
651
652atexit - for registering functions to be called when Python exits.
653
654imputil - Greg Stein's alternative API for writing custom import
655hooks.
656
657pyexpat - an interface to the Expat XML parser, contributed by Paul
658Prescod.
659
660xml - a new package with XML support code organized (so far) in three
661subpackages: xml.dom, xml.sax, and xml.parsers. Describing these
662would fill a volume. There's a special feature whereby a
663user-installed package named _xmlplus overrides the standard
664xmlpackage; this is intended to give the XML SIG a hook to distribute
665backwards-compatible updates to the standard xml package.
666
667webbrowser - a platform-independent API to launch a web browser.
668
669
Guido van Rossume905e952000-09-05 12:42:46 +0000670Changed Modules
671---------------
672
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000673array -- new methods for array objects: count, extend, index, pop, and
674remove
675
676binascii -- new functions b2a_hex and a2b_hex that convert between
677binary data and its hex representation
678
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000679calendar -- Many new functions that support features including control
680over which day of the week is the first day, returning strings instead
681of printing them. Also new symbolic constants for days of week,
682e.g. MONDAY, ..., SUNDAY.
683
684cgi -- FieldStorage objects have a getvalue method that works like a
685dictionary's get method and returns the value attribute of the object.
686
687ConfigParser -- The parser object has new methods has_option,
688remove_section, remove_option, set, and write. They allow the module
689to be used for writing config files as well as reading them.
690
691ftplib -- ntransfercmd(), transfercmd(), and retrbinary() all now
Guido van Rossume905e952000-09-05 12:42:46 +0000692optionally support the RFC 959 REST command.
693
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000694gzip -- readline and readlines now accept optional size arguments
Guido van Rossume905e952000-09-05 12:42:46 +0000695
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000696httplib -- New interfaces and support for HTTP/1.1 by Greg Stein. See
697the module doc strings for details.
Guido van Rossum830ca2a2000-09-05 15:34:16 +0000698
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000699locale -- implement getdefaultlocale for Win32 and Macintosh
700
701marshal -- no longer dumps core when marshaling deeply nested or
702recursive data structures
703
704os -- new functions isatty, seteuid, setegid, setreuid, setregid
705
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000706os/popen2 -- popen2/popen3/popen4 support under Windows. popen2/popen3
707support under Unix.
708
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000709os/pty -- support for openpty and forkpty
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000710
711os.path -- fix semantics of os.path.commonprefix
712
713smtplib -- support for sending very long messages
714
715socket -- new function getfqdn()
716
717readline -- new functions to read, write and truncate history files.
718The readline section of the library reference manual contains an
719example.
720
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000721select -- add interface to poll system call
722
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000723shutil -- new copyfileobj function
724
725SimpleHTTPServer, CGIHTTPServer -- Fix problems with buffering in the
726HTTP server.
727
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000728Tkinter -- optimization of function flatten
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000729
730urllib -- scans environment variables for proxy configuration,
Tim Peters8b092332000-09-05 20:15:25 +0000731e.g. http_proxy.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000732
733whichdb -- recognizes dumbdbm format
Guido van Rossume905e952000-09-05 12:42:46 +0000734
735
736Obsolete Modules
737----------------
738
739None. However note that 1.6 made a whole slew of modules obsolete:
740stdwin, soundex, cml, cmpcache, dircache, dump, find, grep, packmail,
741poly, zmod, strop, util, whatsound.
742
743
744Changed, New, Obsolete Tools
745----------------------------
746
Tim Peters8b092332000-09-05 20:15:25 +0000747None.
Guido van Rossume905e952000-09-05 12:42:46 +0000748
749
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000750C-level Changes
751---------------
752
753Several cleanup jobs were carried out throughout the source code.
754
755All C code was converted to ANSI C; we got rid of all uses of the
756Py_PROTO() macro, which makes the header files a lot more readable.
757
758Most of the portability hacks were moved to a new header file,
759pyport.h; several other new header files were added and some old
760header files were removed, in an attempt to create a more rational set
761of header files. (Few of these ever need to be included explicitly;
762they are all included by Python.h.)
763
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000764Trent Mick ensured portability to 64-bit platforms, under both Linux
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000765and Win64, especially for the new Intel Itanium processor. Mick also
766added large file support for Linux64 and Win64.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000767
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000768The C APIs to return an object's size have been update to consistently
769use the form PyXXX_Size, e.g. PySequence_Size and PyDict_Size. In
770previous versions, the abstract interfaces used PyXXX_Length and the
771concrete interfaces used PyXXX_Size. The old names,
772e.g. PyObject_Length, are still available for backwards compatibility
773at the API level, but are deprecated.
774
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000775The PyOS_CheckStack function has been implemented on Windows by
776Fredrik Lundh. It prevents Python from failing with a stack overflow
777on Windows.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000778
779The GC changes resulted in creation of two new slots on object,
780tp_traverse and tp_clear. The augmented assignment changes result in
Guido van Rossum4338a282000-09-06 13:02:08 +0000781the creation of a new slot for each in-place operator.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000782
783The GC API creates new requirements for container types implemented in
Guido van Rossum4338a282000-09-06 13:02:08 +0000784C extension modules. See Include/objimpl.h for details.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000785
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000786PyErr_Format has been updated to automatically calculate the size of
787the buffer needed to hold the formatted result string. This change
788prevents crashes caused by programmer error.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +0000789
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000790New C API calls: PyObject_AsFileDescriptor, PyErr_WriteUnraisable.
Guido van Rossume905e952000-09-05 12:42:46 +0000791
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000792PyRun_AnyFileEx, PyRun_SimpleFileEx, PyRun_FileEx -- New functions
793that are the same as their non-Ex counterparts except they take an
794extra flag argument that tells them to close the file when done.
795
796XXX There were other API changes that should be fleshed out here.
Guido van Rossumab9d6f01998-08-10 22:01:13 +0000797
Tim Peters8b092332000-09-05 20:15:25 +0000798
799Windows Changes
800---------------
801
802New popen2/popen3/peopen4 in os module (see Changed Modules above).
803
804os.popen is much more usable on Windows 95 and 98. See Microsoft
805Knowledge Base article Q150956. The Win9x workaround described there
806is implemented by the new w9xpopen.exe helper in the root of your
807Python installation. Note that Python uses this internally; it is not
808a standalone program.
809
810Administrator privileges are no longer required to install Python
811on Windows NT or Windows 2000. If you have administrator privileges,
812Python's registry info will be written under HKEY_LOCAL_MACHINE.
813Otherwise the installer backs off to writing Python's registry info
Guido van Rossum4338a282000-09-06 13:02:08 +0000814under HKEY_CURRENT_USER. The latter is sufficient for all "normal"
Tim Peters8b092332000-09-05 20:15:25 +0000815uses of Python, but will prevent some advanced uses from working
816(for example, running a Python script as an NT service, or possibly
817from CGI).
818
819[This was new in 1.6] The installer no longer runs a separate Tcl/Tk
820installer; instead, it installs the needed Tcl/Tk files directly in the
821Python directory. If you already have a Tcl/Tk installation, this
822wastes some disk space (about 4 Megs) but avoids problems with
823conflicting Tcl/Tk installations, and makes it much easier for Python
824to ensure that Tcl/Tk can find all its files.
825
826[This was new in 1.6] The Windows installer now installs by default in
827\Python20\ on the default volume, instead of \Program Files\Python-2.0\.
828
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000829
830Updates to the changes between 1.5.2 and 1.6
831--------------------------------------------
832
833The 1.6 NEWS file can't be changed after the release is done, so here
834is some late-breaking news:
835
836New APIs in locale.py: normalize(), getdefaultlocale(), resetlocale(),
837and changes to getlocale() and setlocale().
838
839The new module is now enabled per default.
840
841It is not true that the encodings codecs cannot be used for normal
842strings: the string.encode() (which is also present on 8-bit strings
843!) allows using them for 8-bit strings too, e.g. to convert files from
844cp1252 (Windows) to latin-1 or vice-versa.
845
846Japanese codecs are available from Tamito KAJIYAMA:
847http://pseudo.grad.sccs.chukyo-u.ac.jp/~kajiyama/python/
848
849
Guido van Rossumab9d6f01998-08-10 22:01:13 +0000850======================================================================