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Tim Petersd7b5e882001-01-25 03:36:26 +00001What's New in Python 2.1 alpha 2?
2=================================
Tim Peters40ead762001-01-27 05:35:26 +00003
Tim Petersd7b5e882001-01-25 03:36:26 +00004Core language, builtins, and interpreter
5
Tim Peters40ead762001-01-27 05:35:26 +00006- repr(string) is easier to read, now using hex escapes instead of octal,
7 and using \t, \n and \r instead of \011, \012 and \015 (respectively):
8
9 >>> "\texample \r\n" + chr(0) + chr(255)
10 '\texample \r\n\x00\xff' # in 2.1
11 '\011example \015\012\000\377' # in 2.0
12
Moshe Zadka6af0ce02001-01-29 06:41:00 +000013- Functions are now compared and hashed by identity, not by value, since
14 the func_code attribute is writable.
15
Tim Petersd7b5e882001-01-25 03:36:26 +000016Standard library
17
Barry Warsaw30dbd142001-01-31 22:14:01 +000018- mailbox.py now has a new class, PortableUnixMailbox which is
19 identical to UnixMailbox but uses a more portable scheme for
20 determining From_ separators. Also, the constructors for all the
21 classes in this module have a new optional `factory' argument, which
22 is a callable used when new message classes must be instantiated by
23 the next() method.
24
Tim Petersd7b5e882001-01-25 03:36:26 +000025- random.py is now self-contained, and offers all the functionality of
26 the now-deprecated whrandom.py. See the docs for details. random.py
27 also supports new functions getstate() and setstate(), for saving
Tim Petersd52269b2001-01-25 06:23:18 +000028 and restoring the internal state of the generator; and jumpahead(n),
29 for quickly forcing the internal state to be the same as if n calls to
30 random() had been made. The latter is particularly useful for multi-
31 threaded programs, creating one instance of the random.Random() class for
32 each thread, then using .jumpahead() to force each instance to use a
33 non-overlapping segment of the full period.
Tim Petersd7b5e882001-01-25 03:36:26 +000034
Tim Petersee826f82001-01-31 19:39:44 +000035Windows changes
36
37- Build procedure: the zlib project is built in a different way that
38 ensures the zlib header files used can no longer get out of synch with
39 the zlib binary used. See PCbuild\readme.txt for details.
40
Tim Petersd7b5e882001-01-25 03:36:26 +000041
Tim Petersa3a3a032000-11-30 05:22:44 +000042What's New in Python 2.1 alpha 1?
43=================================
44
45Core language, builtins, and interpreter
46
Jeremy Hylton69c32792001-01-30 01:27:28 +000047- The compiler will report a SyntaxError if "from ... import *" occurs
48 in a function or class scope or if a name bound by the import
49 statement is declared global in the same scope. The language
50 reference has also documented that these cases are illegal, but
51 they were not enforced.
52
Marc-André Lemburgebb195b2001-01-20 10:34:52 +000053- There is a new Unicode companion to the PyObject_Str() API
54 called PyObject_Unicode(). It behaves in the same way as the
55 former, but assures that the returned value is an Unicode object
56 (applying the usual coercion if necessary).
Marc-André Lemburgad7c98e2001-01-17 17:09:53 +000057
Guido van Rossumf98eda02001-01-17 15:54:45 +000058- The comparison operators support "rich comparison overloading" (PEP
59 207). C extension types can provide a rich comparison function in
60 the new tp_richcompare slot in the type object. The cmp() function
61 and the C function PyObject_Compare() first try the new rich
62 comparison operators before trying the old 3-way comparison. There
63 is also a new C API PyObject_RichCompare() (which also falls back on
64 the old 3-way comparison, but does not constrain the outcome of the
65 rich comparison to a Boolean result).
66
67 The rich comparison function takes two objects (at least one of
68 which is guaranteed to have the type that provided the function) and
69 an integer indicating the opcode, which can be Py_LT, Py_LE, Py_EQ,
70 Py_NE, Py_GT, Py_GE (for <, <=, ==, !=, >, >=), and returns a Python
71 object, which may be NotImplemented (in which case the tp_compare
72 slot function is used as a fallback, if defined).
73
74 Classes can overload individual comparison operators by defining one
75 or more of the methods__lt__, __le__, __eq__, __ne__, __gt__,
Guido van Rossuma88479f2001-01-18 14:28:08 +000076 __ge__. There are no explicit "reflected argument" versions of
77 these; instead, __lt__ and __gt__ are each other's reflection,
78 likewise for__le__ and __ge__; __eq__ and __ne__ are their own
79 reflection (similar at the C level). No other implications are
80 made; in particular, Python does not assume that == is the Boolean
81 inverse of !=, or that < is the Boolean inverse of >=. This makes
82 it possible to define types with partial orderings.
Guido van Rossumf98eda02001-01-17 15:54:45 +000083
84 Classes or types that want to implement (in)equality tests but not
85 the ordering operators (i.e. unordered types) should implement ==
86 and !=, and raise an error for the ordering operators.
87
Guido van Rossuma88479f2001-01-18 14:28:08 +000088 It is possible to define types whose rich comparison results are not
Guido van Rossumf98eda02001-01-17 15:54:45 +000089 Boolean; e.g. a matrix type might want to return a matrix of bits
90 for A < B, giving elementwise comparisons. Such types should ensure
91 that any interpretation of their value in a Boolean context raises
92 an exception, e.g. by defining __nonzero__ (or the tp_nonzero slot
93 at the C level) to always raise an exception.
94
Guido van Rossuma88479f2001-01-18 14:28:08 +000095- Complex numbers use rich comparisons to define == and != but raise
96 an exception for <, <=, > and >=. Unfortunately, this also means
97 that cmp() of two complex numbers raises an exception when the two
98 numbers differ. Since it is not mathematically meaningful to compare
99 complex numbers except for equality, I hope that this doesn't break
100 too much code.
101
Barry Warsaw573b5412001-01-15 20:43:18 +0000102- Functions and methods now support getting and setting arbitrarily
103 named attributes (PEP 232). Functions have a new __dict__
104 (a.k.a. func_dict) which hold the function attributes. Methods get
105 and set attributes on their underlying im_func. It is a TypeError
106 to set an attribute on a bound method.
107
Guido van Rossum051e3352001-01-15 19:11:10 +0000108- The xrange() object implementation has been improved so that
109 xrange(sys.maxint) can be used on 64-bit platforms. There's still a
110 limitation that in this case len(xrange(sys.maxint)) can't be
111 calculated, but the common idiom "for i in xrange(sys.maxint)" will
112 work fine as long as the index i doesn't actually reach 2**31.
113 (Python uses regular ints for sequence and string indices; fixing
114 that is much more work.)
115
Guido van Rossum1cc8f832001-01-12 16:25:08 +0000116- Two changes to from...import:
117
118 1) "from M import X" now works even if M is not a real module; it's
119 basically a getattr() operation with AttributeError exceptions
120 changed into ImportError.
121
122 2) "from M import *" now looks for M.__all__ to decide which names to
123 import; if M.__all__ doesn't exist, it uses M.__dict__.keys() but
124 filters out names starting with '_' as before. Whether or not
125 __all__ exists, there's no restriction on the type of M.
126
Guido van Rossumf61f1662001-01-10 20:13:55 +0000127- File objects have a new method, xreadlines(). This is the fastest
128 way to iterate over all lines in a file:
129
130 for line in file.xreadlines():
131 ...do something to line...
132
133 See the xreadlines module (mentioned below) for how to do this for
134 other file-like objects.
135
136- Even if you don't use file.xreadlines(), you may expect a speedup on
137 line-by-line input. The file.readline() method has been optimized
Tim Petersf29b64d2001-01-15 06:33:19 +0000138 quite a bit in platform-specific ways: on systems (like Linux) that
139 support flockfile(), getc_unlocked(), and funlockfile(), those are
140 used by default. On systems (like Windows) without getc_unlocked(),
141 a complicated (but still thread-safe) method using fgets() is used by
142 default.
143
Tim Petersd52269b2001-01-25 06:23:18 +0000144 You can force use of the fgets() method by #define'ing
145 USE_FGETS_IN_GETLINE at build time (it may be faster than
Tim Petersf29b64d2001-01-15 06:33:19 +0000146 getc_unlocked()).
147
Tim Petersd52269b2001-01-25 06:23:18 +0000148 You can force fgets() not to be used by #define'ing
149 DONT_USE_FGETS_IN_GETLINE (this is the first thing to try if std test
Tim Petersf29b64d2001-01-15 06:33:19 +0000150 test_bufio.py fails -- and let us know if it does!).
151
152- In addition, the fileinput module, while still slower than the other
153 methods on most platforms, has been sped up too, by using
154 file.readlines(sizehint).
Guido van Rossumf61f1662001-01-10 20:13:55 +0000155
156- Support for run-time warnings has been added, including a new
157 command line option (-W) to specify the disposition of warnings.
158 See the description of the warnings module below.
159
160- Extensive changes have been made to the coercion code. This mostly
161 affects extension modules (which can now implement mixed-type
162 numerical operators without having to use coercion), but
163 occasionally, in boundary cases the coercion semantics have changed
164 subtly. Since this was a terrible gray area of the language, this
Guido van Rossumae72d872001-01-11 15:00:14 +0000165 is considered an improvement. Also note that __rcmp__ is no longer
Guido van Rossumf61f1662001-01-10 20:13:55 +0000166 supported -- instead of calling __rcmp__, __cmp__ is called with
Guido van Rossuma88479f2001-01-18 14:28:08 +0000167 reflected arguments.
Guido van Rossumf61f1662001-01-10 20:13:55 +0000168
Guido van Rossumf98eda02001-01-17 15:54:45 +0000169- In connection with the coercion changes, a new built-in singleton
170 object, NotImplemented is defined. This can be returned for
171 operations that wish to indicate they are not implemented for a
172 particular combination of arguments. From C, this is
173 Py_NotImplemented.
174
Martin v. Löwisbe4c0f52001-01-04 20:30:56 +0000175- The interpreter accepts now bytecode files on the command line even
176 if they do not have a .pyc or .pyo extension. On Linux, after executing
177
178 echo ':pyc:M::\x87\xc6\x0d\x0a::/usr/local/bin/python:' > /proc/sys/fs/binfmt_misc/register
179
180 any byte code file can be used as an executable (i.e. as an argument
181 to execve(2)).
182
Tim Peters9940b802000-12-01 07:59:35 +0000183- %[xXo] formats of negative Python longs now produce a sign
Tim Petersa3a3a032000-11-30 05:22:44 +0000184 character. In 1.6 and earlier, they never produced a sign,
185 and raised an error if the value of the long was too large
186 to fit in a Python int. In 2.0, they produced a sign if and
187 only if too large to fit in an int. This was inconsistent
188 across platforms (because the size of an int varies across
189 platforms), and inconsistent with hex() and oct(). Example:
190
191 >>> "%x" % -0x42L
Tim Peters9940b802000-12-01 07:59:35 +0000192 '-42' # in 2.1
Tim Petersa3a3a032000-11-30 05:22:44 +0000193 'ffffffbe' # in 2.0 and before, on 32-bit machines
194 >>> hex(-0x42L)
195 '-0x42L' # in all versions of Python
196
Tim Peters9940b802000-12-01 07:59:35 +0000197 The behavior of %d formats for negative Python longs remains
198 the same as in 2.0 (although in 1.6 and before, they raised
199 an error if the long didn't fit in a Python int).
200
201 %u formats don't make sense for Python longs, but are allowed
202 and treated the same as %d in 2.1. In 2.0, a negative long
203 formatted via %u produced a sign if and only if too large to
204 fit in an int. In 1.6 and earlier, a negative long formatted
205 via %u raised an error if it was too big to fit in an int.
206
Guido van Rossum3661d392000-12-12 22:10:31 +0000207- Dictionary objects have an odd new method, popitem(). This removes
208 an arbitrary item from the dictionary and returns it (in the form of
209 a (key, value) pair). This can be useful for algorithms that use a
210 dictionary as a bag of "to do" items and repeatedly need to pick one
211 item. Such algorithms normally end up running in quadratic time;
212 using popitem() they can usually be made to run in linear time.
213
Tim Peters36cdad12000-12-29 02:06:45 +0000214Standard library
215
Thomas Woutersfe385252001-01-19 23:16:56 +0000216- In the time module, the time argument to the functions strftime,
217 localtime, gmtime, asctime and ctime is now optional, defaulting to
218 the current time (in the local timezone).
219
Guido van Rossumda91f222001-01-15 16:36:08 +0000220- The ftplib module now defaults to passive mode, which is deemed a
221 more useful default given that clients are often inside firewalls
222 these days. Note that this could break if ftplib is used to connect
223 to a *server* that is inside a firewall, from outside; this is
224 expected to be a very rare situation. To fix that, you can call
225 ftp.set_pasv(0).
226
Martin v. Löwis10a27872001-01-13 09:54:41 +0000227- The module site now treats .pth files not only for path configuration,
228 but also supports extensions to the initialization code: Lines starting
229 with import are executed.
230
Guido van Rossumf61f1662001-01-10 20:13:55 +0000231- There's a new module, warnings, which implements a mechanism for
232 issuing and filtering warnings. There are some new built-in
233 exceptions that serve as warning categories, and a new command line
234 option, -W, to control warnings (e.g. -Wi ignores all warnings, -We
235 turns warnings into errors). warnings.warn(message[, category])
236 issues a warning message; this can also be called from C as
237 PyErr_Warn(category, message).
238
239- A new module xreadlines was added. This exports a single factory
240 function, xreadlines(). The intention is that this code is the
241 absolutely fastest way to iterate over all lines in an open
242 file(-like) object:
243
244 import xreadlines
245 for line in xreadlines.xreadlines(file):
246 ...do something to line...
247
248 This is equivalent to the previous the speed record holder using
249 file.readlines(sizehint). Note that if file is a real file object
250 (as opposed to a file-like object), this is equivalent:
251
252 for line in file.xreadlines():
253 ...do something to line...
254
Tim Peters36cdad12000-12-29 02:06:45 +0000255- The bisect module has new functions bisect_left, insort_left,
256 bisect_right and insort_right. The old names bisect and insort
257 are now aliases for bisect_right and insort_right. XXX_right
258 and XXX_left methods differ in what happens when the new element
259 compares equal to one or more elements already in the list: the
260 XXX_left methods insert to the left, the XXX_right methods to the
Tim Peters742bb6f2001-01-05 08:05:32 +0000261 right. Code that doesn't care where equal elements end up should
262 continue to use the old, short names ("bisect" and "insort").
Tim Peters36cdad12000-12-29 02:06:45 +0000263
Andrew M. Kuchlingf6f3a892001-01-13 14:53:34 +0000264- The new curses.panel module wraps the panel library that forms part
265 of SYSV curses and ncurses. Contributed by Thomas Gellekum.
266
Guido van Rossumf61f1662001-01-10 20:13:55 +0000267- The SocketServer module now sets the allow_reuse_address flag by
268 default in the TCPServer class.
269
270- A new function, sys._getframe(), returns the stack frame pointer of
271 the caller. This is intended only as a building block for
272 higher-level mechanisms such as string interpolation.
273
274Build issues
275
Guido van Rossum1e33bdc2001-01-23 03:17:00 +0000276- For Unix (and Unix-compatible) builds, configuration and building of
277 extension modules is now greatly automated. Rather than having to
278 edit the Modules/Setup file to indicate which modules should be
279 built and where their include files and libraries are, a
280 distutils-based setup.py script now takes care of building most
281 extension modules. All extension modules built this way are built
282 as shared libraries. Only a few modules that must be linked
283 statically are still listed in the Setup file; you won't need to
284 edit their configuration.
285
286- Python should now build out of the box on Cygwin. If it doesn't,
287 mail to Jason Tishler (jlt63 at users.sourceforge.net).
Guido van Rossumf61f1662001-01-10 20:13:55 +0000288
289- Python now always uses its own (renamed) implementation of getopt()
290 -- there's too much variation among C library getopt()
291 implementations.
292
293- C++ compilers are better supported; the CXX macro is always set to a
294 C++ compiler if one is found.
Tim Peters36cdad12000-12-29 02:06:45 +0000295
Tim Petersd92dfe02000-12-12 01:18:41 +0000296Windows changes
297
298- select module: By default under Windows, a select() call
299 can specify no more than 64 sockets. Python now boosts
300 this Microsoft default to 512. If you need even more than
301 that, see the MS docs (you'll need to #define FD_SETSIZE
302 and recompile Python from source).
303
Guido van Rossumf61f1662001-01-10 20:13:55 +0000304- Support for Windows 3.1, DOS and OS/2 is gone. The Lib/dos-8x3
305 subdirectory is no more!
306
Tim Petersa3a3a032000-11-30 05:22:44 +0000307
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000308What's New in Python 2.0?
Fred Drake1a640502000-10-16 20:27:25 +0000309=========================
Guido van Rossum61000331997-08-15 04:39:58 +0000310
Guido van Rossum8ed602b2000-09-01 22:34:33 +0000311Below is a list of all relevant changes since release 1.6. Older
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000312changes are in the file HISTORY. If you are making the jump directly
313from Python 1.5.2 to 2.0, make sure to read the section for 1.6 in the
314HISTORY file! Many important changes listed there.
Guido van Rossum61000331997-08-15 04:39:58 +0000315
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000316Alternatively, a good overview of the changes between 1.5.2 and 2.0 is
317the document "What's New in Python 2.0" by Kuchling and Moshe Zadka:
318http://starship.python.net/crew/amk/python/writing/new-python/.
Guido van Rossum1f83cce1997-10-06 21:04:35 +0000319
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000320--Guido van Rossum (home page: http://www.pythonlabs.com/~guido/)
Guido van Rossum437cfe81999-04-08 20:17:57 +0000321
322======================================================================
323
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000324What's new in 2.0 (since release candidate 1)?
325==============================================
326
327Standard library
328
329- The copy_reg module was modified to clarify its intended use: to
330 register pickle support for extension types, not for classes.
331 pickle() will raise a TypeError if it is passed a class.
332
333- Fixed a bug in gettext's "normalize and expand" code that prevented
334 it from finding an existing .mo file.
335
336- Restored support for HTTP/0.9 servers in httplib.
337
Tim Peters989b7b92000-10-16 20:24:53 +0000338- The math module was changed to stop raising OverflowError in case of
339 underflow, and return 0 instead in underflow cases. Whether Python
340 used to raise OverflowError in case of underflow was platform-
341 dependent (it did when the platform math library set errno to ERANGE
342 on underflow).
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000343
344- Fixed a bug in StringIO that occurred when the file position was not
345 at the end of the file and write() was called with enough data to
346 extend past the end of the file.
347
348- Fixed a bug that caused Tkinter error messages to get lost on
349 Windows. The bug was fixed by replacing direct use of
350 interp->result with Tcl_GetStringResult(interp).
351
352- Fixed bug in urllib2 that caused it to fail when it received an HTTP
353 redirect response.
354
355- Several changes were made to distutils: Some debugging code was
356 removed from util. Fixed the installer used when an external zip
357 program (like WinZip) is not found; the source code for this
358 installer is in Misc/distutils. check_lib() was modified to behave
359 more like AC_CHECK_LIB by add other_libraries() as a parameter. The
360 test for whether installed modules are on sys.path was changed to
361 use both normcase() and normpath().
362
Jeremy Hyltond867a2c2000-10-16 20:41:38 +0000363- Several minor bugs were fixed in the xml package (the minidom,
364 pulldom, expatreader, and saxutils modules).
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000365
366- The regression test driver (regrtest.py) behavior when invoked with
367 -l changed: It now reports a count of objects that are recognized as
368 garbage but not freed by the garbage collector.
369
Tim Peters989b7b92000-10-16 20:24:53 +0000370- The regression test for the math module was changed to test
371 exceptional behavior when the test is run in verbose mode. Python
372 cannot yet guarantee consistent exception behavior across platforms,
373 so the exception part of test_math is run only in verbose mode, and
374 may fail on your platform.
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000375
376Internals
377
378- PyOS_CheckStack() has been disabled on Win64, where it caused
379 test_sre to fail.
380
381Build issues
382
383- Changed compiler flags, so that gcc is always invoked with -Wall and
384 -Wstrict-prototypes. Users compiling Python with GCC should see
385 exactly one warning, except if they have passed configure the
Tim Peters989b7b92000-10-16 20:24:53 +0000386 --with-pydebug flag. The expected warning is for getopt() in
Tim Petersadfb94f2000-10-16 20:51:33 +0000387 Modules/main.c. This warning will be fixed for Python 2.1.
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000388
Tim Petersa3a3a032000-11-30 05:22:44 +0000389- Fixed configure to add -threads argument during linking on OSF1.
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000390
391Tools and other miscellany
392
393- The compiler in Tools/compiler was updated to support the new
394 language features introduced in 2.0: extended print statement, list
395 comprehensions, and augmented assignments. The new compiler should
396 also be backwards compatible with Python 1.5.2; the compiler will
397 always generate code for the version of the interpreter it runs
Tim Petersa3a3a032000-11-30 05:22:44 +0000398 under.
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000399
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000400What's new in 2.0 release candidate 1 (since beta 2)?
401=====================================================
402
Jeremy Hylton6040aaa2000-10-09 21:27:22 +0000403What is release candidate 1?
404
405We believe that release candidate 1 will fix all known bugs that we
406intend to fix for the 2.0 final release. This release should be a bit
407more stable than the previous betas. We would like to see even more
408widespread testing before the final release, so we are producing this
409release candidate. The final release will be exactly the same unless
410any show-stopping (or brown bag) bugs are found by testers of the
411release candidate.
412
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000413All the changes since the last beta release are bug fixes or changes
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000414to support building Python for specific platforms.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000415
416Core language, builtins, and interpreter
417
418- A bug that caused crashes when __coerce__ was used with augmented
419 assignment, e.g. +=, was fixed.
420
421- Raise ZeroDivisionError when raising zero to a negative number,
422 e.g. 0.0 ** -2.0. Note that math.pow is unrelated to the builtin
423 power operator and the result of math.pow(0.0, -2.0) will vary by
424 platform. On Linux, it raises a ValueError.
425
426- A bug in Unicode string interpolation was fixed that occasionally
427 caused errors with formats including "%%". For example, the
428 following expression "%% %s" % u"abc" no longer raises a TypeError.
429
430- Compilation of deeply nested expressions raises MemoryError instead
431 of SyntaxError, e.g. eval("[" * 50 + "]" * 50).
432
433- In 2.0b2 on Windows, the interpreter wrote .pyc files in text mode,
434 rendering them useless. They are now written in binary mode again.
435
436Standard library
437
438- Keyword arguments are now accepted for most pattern and match object
439 methods in SRE, the standard regular expression engine.
440
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000441- In SRE, fixed error with negative lookahead and lookbehind that
Jeremy Hylton32e20ff2000-10-09 19:48:11 +0000442 manifested itself as a runtime error in patterns like "(?<!abc)(def)".
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000443
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000444- Several bugs in the Unicode handling and error handling in _tkinter
445 were fixed.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000446
447- Fix memory management errors in Merge() and Tkapp_Call() routines.
448
449- Several changes were made to cStringIO to make it compatible with
450 the file-like object interface and with StringIO. If operations are
451 performed on a closed object, an exception is raised. The truncate
452 method now accepts a position argument and readline accepts a size
Tim Petersa3a3a032000-11-30 05:22:44 +0000453 argument.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000454
455- There were many changes made to the linuxaudiodev module and its
456 test suite; as a result, a short, unexpected audio sample should now
Tim Petersa3a3a032000-11-30 05:22:44 +0000457 play when the regression test is run.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000458
459 Note that this module is named poorly, because it should work
460 correctly on any platform that supports the Open Sound System
Tim Petersa3a3a032000-11-30 05:22:44 +0000461 (OSS).
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000462
463 The module now raises exceptions when errors occur instead of
464 crashing. It also defines the AFMT_A_LAW format (logarithmic A-law
465 audio) and defines a getptr() method that calls the
466 SNDCTL_DSP_GETxPTR ioctl defined in the OSS Programmer's Guide.
467
468- The library_version attribute, introduced in an earlier beta, was
469 removed because it can not be supported with early versions of the C
470 readline library, which provides no way to determine the version at
471 compile-time.
472
473- The binascii module is now enabled on Win64.
474
Tim Peters46446d62000-10-09 21:19:31 +0000475- tokenize.py no longer suffers "recursion depth" errors when parsing
476 programs with very long string literals.
477
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000478Internals
479
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000480- Fixed several buffer overflow vulnerabilities in calculate_path(),
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000481 which is called when the interpreter starts up to determine where
482 the standard library is installed. These vulnerabilities affect all
483 previous versions of Python and can be exploited by setting very
484 long values for PYTHONHOME or argv[0]. The risk is greatest for a
485 setuid Python script, although use of the wrapper in
486 Misc/setuid-prog.c will eliminate the vulnerability.
487
488- Fixed garbage collection bugs in instance creation that were
489 triggered when errors occurred during initialization. The solution,
490 applied in cPickle and in PyInstance_New(), is to call
491 PyObject_GC_Init() after the initialization of the object's
492 container attributes is complete.
493
494- pyexpat adds definitions of PyModule_AddStringConstant and
495 PyModule_AddObject if the Python version is less than 2.0, which
496 provides compatibility with PyXML on Python 1.5.2.
497
498- If the platform has a bogus definition for LONG_BIT (the number of
499 bits in a long), an error will be reported at compile time.
500
501- Fix bugs in _PyTuple_Resize() which caused hard-to-interpret garbage
502 collection crashes and possibly other, unreported crashes.
503
504- Fixed a memory leak in _PyUnicode_Fini().
505
506Build issues
507
508- configure now accepts a --with-suffix option that specifies the
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000509 executable suffix. This is useful for builds on Cygwin and Mac OS
Tim Petersa3a3a032000-11-30 05:22:44 +0000510 X, for example.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000511
512- The mmap.PAGESIZE constant is now initialized using sysconf when
513 possible, which eliminates a dependency on -lucb for Reliant UNIX.
514
515- The md5 file should now compile on all platforms.
516
517- The select module now compiles on platforms that do not define
518 POLLRDNORM and related constants.
519
520- Darwin (Mac OS X): Initial support for static builds on this
Tim Petersa3a3a032000-11-30 05:22:44 +0000521 platform.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000522
Jeremy Hylton10921202000-10-09 18:34:12 +0000523- BeOS: A number of changes were made to the build and installation
524 process. ar-fake now operates on a directory of object files.
525 dl_export.h is gone, and its macros now appear on the mwcc command
526 line during build on PPC BeOS.
527
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000528- Platform directory in lib/python2.0 is "plat-beos5" (or
Jeremy Hylton10921202000-10-09 18:34:12 +0000529 "plat-beos4", if building on BeOS 4.5), rather than "plat-beos".
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000530
531- Cygwin: Support for shared libraries, Tkinter, and sockets.
532
533- SunOS 4.1.4_JL: Fix test for directory existence in configure.
534
535Tools and other miscellany
536
537- Removed debugging prints from main used with freeze.
538
Tim Peters46446d62000-10-09 21:19:31 +0000539- IDLE auto-indent no longer crashes when it encounters Unicode
540 characters.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000541
542What's new in 2.0 beta 2 (since beta 1)?
543========================================
544
545Core language, builtins, and interpreter
546
Tim Peters482c0212000-09-26 06:33:09 +0000547- Add support for unbounded ints in %d,i,u,x,X,o formats; for example
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000548 "%d" % 2L**64 == "18446744073709551616".
Jeremy Hylton1b618592000-09-26 05:32:36 +0000549
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000550- Add -h and -V command line options to print the usage message and
551 Python version number and exit immediately.
552
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000553- eval() and exec accept Unicode objects as code parameters.
554
555- getattr() and setattr() now also accept Unicode objects for the
556 attribute name, which are converted to strings using the default
557 encoding before lookup.
558
559- Multiplication on string and Unicode now does proper bounds
560 checking; e.g. 'a' * 65536 * 65536 will raise ValueError, "repeated
561 string is too long."
562
563- Better error message when continue is found in try statement in a
Tim Petersa3a3a032000-11-30 05:22:44 +0000564 loop.
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000565
Jeremy Hylton1b618592000-09-26 05:32:36 +0000566
567Standard library and extensions
568
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000569- array: reverse() method of array now works. buffer_info() now does
Jeremy Hylton1b618592000-09-26 05:32:36 +0000570 argument checking; it still takes no arguments.
571
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000572- asyncore/asynchat: Included most recent version from Sam Rushing.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000573
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000574- cgi: Accept '&' or ';' as separator characters when parsing form data.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000575
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000576- CGIHTTPServer: Now works on Windows (and perhaps even Mac).
Jeremy Hylton1b618592000-09-26 05:32:36 +0000577
578- ConfigParser: When reading the file, options spelled in upper case
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000579 letters are now correctly converted to lowercase.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000580
581- copy: Copy Unicode objects atomically.
582
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000583- cPickle: Fail gracefully when copy_reg can't be imported.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000584
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000585- cStringIO: Implemented readlines() method.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000586
Fred Drake67233bc2000-09-26 16:40:27 +0000587- dbm: Add get() and setdefault() methods to dbm object. Add constant
588 `library' to module that names the library used. Added doc strings
589 and method names to error messages. Uses configure to determine
590 which ndbm.h file to include; Berkeley DB's nbdm and GDBM's ndbm is
591 now available options.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000592
593- distutils: Update to version 0.9.3.
594
595- dl: Add several dl.RTLD_ constants.
596
597- fpectl: Now supported on FreeBSD.
598
599- gc: Add DEBUG_SAVEALL option. When enabled all garbage objects
600 found by the collector will be saved in gc.garbage. This is useful
601 for debugging a program that creates reference cycles.
602
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000603- httplib: Three changes: Restore support for set_debuglevel feature
Jeremy Hylton1b618592000-09-26 05:32:36 +0000604 of HTTP class. Do not close socket on zero-length response. Do not
605 crash when server sends invalid content-length header.
606
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000607- mailbox: Mailbox class conforms better to qmail specifications.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000608
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000609- marshal: When reading a short, sign-extend on platforms where shorts
610 are bigger than 16 bits. When reading a long, repair the unportable
611 sign extension that was being done for 64-bit machines. (It assumed
612 that signed right shift sign-extends.)
613
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000614- operator: Add contains(), invert(), __invert__() as aliases for
615 __contains__(), inv(), and __inv__() respectively.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000616
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000617- os: Add support for popen2() and popen3() on all platforms where
618 fork() exists. (popen4() is still in the works.)
Jeremy Hylton1b618592000-09-26 05:32:36 +0000619
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000620- os: (Windows only:) Add startfile() function that acts like double-
Tim Peters482c0212000-09-26 06:33:09 +0000621 clicking on a file in Explorer (or passing the file name to the
622 DOS "start" command).
Jeremy Hylton1b618592000-09-26 05:32:36 +0000623
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000624- os.path: (Windows, DOS:) Treat trailing colon correctly in
Tim Peters482c0212000-09-26 06:33:09 +0000625 os.path.join. os.path.join("a:", "b") yields "a:b".
Jeremy Hylton1b618592000-09-26 05:32:36 +0000626
627- pickle: Now raises ValueError when an invalid pickle that contains
628 a non-string repr where a string repr was expected. This behavior
629 matches cPickle.
630
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000631- posixfile: Remove broken __del__() method.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000632
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000633- py_compile: support CR+LF line terminators in source file.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000634
635- readline: Does not immediately exit when ^C is hit when readline and
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000636 threads are configured. Adds definition of rl_library_version. (The
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000637 latter addition requires GNU readline 2.2 or later.)
Jeremy Hylton1b618592000-09-26 05:32:36 +0000638
639- rfc822: Domain literals returned by AddrlistClass method
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000640 getdomainliteral() are now properly wrapped in brackets.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000641
642- site: sys.setdefaultencoding() should only be called in case the
Tim Peters482c0212000-09-26 06:33:09 +0000643 standard default encoding ("ascii") is changed. This saves quite a
Jeremy Hylton1b618592000-09-26 05:32:36 +0000644 few cycles during startup since the first call to
645 setdefaultencoding() will initialize the codec registry and the
646 encodings package.
647
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000648- socket: Support for size hint in readlines() method of object returned
649 by makefile().
Jeremy Hylton1b618592000-09-26 05:32:36 +0000650
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000651- sre: Added experimental expand() method to match objects. Does not
Jeremy Hylton625915e2000-10-02 13:43:33 +0000652 use buffer interface on Unicode strings. Does not hang if group id
Jeremy Hylton1b618592000-09-26 05:32:36 +0000653 is followed by whitespace.
654
Tim Petersa3a3a032000-11-30 05:22:44 +0000655- StringIO: Size hint in readlines() is now supported as documented.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000656
657- struct: Check ranges for bytes and shorts.
658
659- urllib: Improved handling of win32 proxy settings. Fixed quote and
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000660 quote_plus functions so that the always encode a comma.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000661
662- Tkinter: Image objects are now guaranteed to have unique ids. Set
663 event.delta to zero if Tk version doesn't support mousewheel.
664 Removed some debugging prints.
665
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000666- UserList: now implements __contains__().
Jeremy Hylton1b618592000-09-26 05:32:36 +0000667
Fred Drake67233bc2000-09-26 16:40:27 +0000668- webbrowser: On Windows, use os.startfile() instead of os.popen(),
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000669 which works around a bug in Norton AntiVirus 2000 that leads directly
670 to a Blue Screen freeze.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000671
672- xml: New version detection code allows PyXML to override standard
673 XML package if PyXML version is greater than 0.6.1.
674
Fred Drake64bb3802000-09-26 16:21:35 +0000675- xml.dom: DOM level 1 support for basic XML. Includes xml.dom.minidom
676 (conventional DOM), and xml.dom.pulldom, which allows building the DOM
677 tree only for nodes which are sufficiently interesting to a specific
678 application. Does not provide the HTML-specific extensions. Still
679 undocumented.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000680
Fred Drake64bb3802000-09-26 16:21:35 +0000681- xml.sax: SAX 2 support for Python, including all the handler
682 interfaces needed to process XML 1.0 compliant XML. Some
683 documentation is already available.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000684
Fred Drake64bb3802000-09-26 16:21:35 +0000685- pyexpat: Renamed to xml.parsers.expat since this is part of the new,
686 packagized XML support.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000687
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000688
Jeremy Hylton1b618592000-09-26 05:32:36 +0000689C API
690
691- Add three new convenience functions for module initialization --
692 PyModule_AddObject(), PyModule_AddIntConstant(), and
693 PyModule_AddStringConstant().
694
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000695- Cleaned up definition of NULL in C source code; all definitions were
Jeremy Hylton1b618592000-09-26 05:32:36 +0000696 removed and add #error to Python.h if NULL isn't defined after
697 #include of stdio.h.
698
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000699- Py_PROTO() macros that were removed in 2.0b1 have been restored for
Jeremy Hylton1b618592000-09-26 05:32:36 +0000700 backwards compatibility (at the source level) with old extensions.
701
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000702- A wrapper API was added for signal() and sigaction(). Instead of
703 either function, always use PyOS_getsig() to get a signal handler
704 and PyOS_setsig() to set one. A new convenience typedef
705 PyOS_sighandler_t is defined for the type of signal handlers.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000706
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000707- Add PyString_AsStringAndSize() function that provides access to the
Jeremy Hylton1b618592000-09-26 05:32:36 +0000708 internal data buffer and size of a string object -- or the default
709 encoded version of a Unicode object.
710
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000711- PyString_Size() and PyString_AsString() accept Unicode objects.
712
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000713- The standard header <limits.h> is now included by Python.h (if it
Fred Drake64bb3802000-09-26 16:21:35 +0000714 exists). INT_MAX and LONG_MAX will always be defined, even if
715 <limits.h> is not available.
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000716
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000717- PyFloat_FromString takes a second argument, pend, that was
718 effectively useless. It is now officially useless but preserved for
719 backwards compatibility. If the pend argument is not NULL, *pend is
720 set to NULL.
721
722- PyObject_GetAttr() and PyObject_SetAttr() now accept Unicode objects
723 for the attribute name. See note on getattr() above.
724
725- A few bug fixes to argument processing for Unicode.
726 PyArg_ParseTupleAndKeywords() now accepts "es#" and "es".
727 PyArg_Parse() special cases "s#" for Unicode objects; it returns a
728 pointer to the default encoded string data instead of to the raw
Tim Petersa3a3a032000-11-30 05:22:44 +0000729 UTF-16.
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000730
731- Py_BuildValue accepts B format (for bgen-generated code).
732
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000733
Jeremy Hylton1b618592000-09-26 05:32:36 +0000734Internals
735
736- On Unix, fix code for finding Python installation directory so that
737 it works when argv[0] is a relative path.
738
Andrew M. Kuchlinga1099be2000-12-15 01:16:43 +0000739- Added a true unicode_internal_encode() function and fixed the
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000740 unicode_internal_decode function() to support Unicode objects directly
Jeremy Hylton1b618592000-09-26 05:32:36 +0000741 rather than by generating a copy of the object.
742
Tim Peters482c0212000-09-26 06:33:09 +0000743- Several of the internal Unicode tables are much smaller now, and
744 the source code should be much friendlier to weaker compilers.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000745
Jeremy Hylton97693b02000-09-26 17:42:51 +0000746- In the garbage collector: Fixed bug in collection of tuples. Fixed
747 bug that caused some instances to be removed from the container set
748 while they were still live. Fixed parsing in gc.set_debug() for
749 platforms where sizeof(long) > sizeof(int).
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000750
751- Fixed refcount problem in instance deallocation that only occurred
752 when Py_REF_DEBUG was defined and Py_TRACE_REFS was not.
753
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000754- On Windows, getpythonregpath is now protected against null data in
755 registry key.
756
757- On Unix, create .pyc/.pyo files with O_EXCL flag to avoid a race
Tim Petersa3a3a032000-11-30 05:22:44 +0000758 condition.
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000759
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000760
Jeremy Hylton1b618592000-09-26 05:32:36 +0000761Build and platform-specific issues
762
763- Better support of GNU Pth via --with-pth configure option.
764
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000765- Python/C API now properly exposed to dynamically-loaded extension
766 modules on Reliant UNIX.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000767
768- Changes for the benefit of SunOS 4.1.4 (really!). mmapmodule.c:
769 Don't define MS_SYNC to be zero when it is undefined. Added missing
770 prototypes in posixmodule.c.
771
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000772- Improved support for HP-UX build. Threads should now be correctly
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000773 configured (on HP-UX 10.20 and 11.00).
Jeremy Hylton1b618592000-09-26 05:32:36 +0000774
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000775- Fix largefile support on older NetBSD systems and OpenBSD by adding
776 define for TELL64.
777
778
779Tools and other miscellany
780
781- ftpmirror: Call to main() is wrapped in if __name__ == "__main__".
782
783- freeze: The modulefinder now works with 2.0 opcodes.
784
Tim Petersa3a3a032000-11-30 05:22:44 +0000785- IDLE:
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000786 Move hackery of sys.argv until after the Tk instance has been
787 created, which allows the application-specific Tkinter
788 initialization to be executed if present; also pass an explicit
789 className parameter to the Tk() constructor.
Fred Drake64bb3802000-09-26 16:21:35 +0000790
Jeremy Hylton1b618592000-09-26 05:32:36 +0000791
792What's new in 2.0 beta 1?
793=========================
794
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000795Source Incompatibilities
796------------------------
797
798None. Note that 1.6 introduced several incompatibilities with 1.5.2,
799such as single-argument append(), connect() and bind(), and changes to
800str(long) and repr(float).
801
802
803Binary Incompatibilities
804------------------------
805
806- Third party extensions built for Python 1.5.x or 1.6 cannot be used
807with Python 2.0; these extensions will have to be rebuilt for Python
8082.0.
809
810- On Windows, attempting to import a third party extension built for
811Python 1.5.x or 1.6 results in an immediate crash; there's not much we
812can do about this. Check your PYTHONPATH environment variable!
813
814- Python bytecode files (*.pyc and *.pyo) are not compatible between
815releases.
816
817
818Overview of Changes Since 1.6
819-----------------------------
820
821There are many new modules (including brand new XML support through
822the xml package, and i18n support through the gettext module); a list
823of all new modules is included below. Lots of bugs have been fixed.
824
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000825The process for making major new changes to the language has changed
826since Python 1.6. Enhancements must now be documented by a Python
827Enhancement Proposal (PEP) before they can be accepted.
828
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000829There are several important syntax enhancements, described in more
830detail below:
831
832 - Augmented assignment, e.g. x += 1
833
834 - List comprehensions, e.g. [x**2 for x in range(10)]
835
836 - Extended import statement, e.g. import Module as Name
837
838 - Extended print statement, e.g. print >> file, "Hello"
839
840Other important changes:
841
842 - Optional collection of cyclical garbage
843
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000844Python Enhancement Proposal (PEP)
845---------------------------------
846
847PEP stands for Python Enhancement Proposal. A PEP is a design
848document providing information to the Python community, or describing
849a new feature for Python. The PEP should provide a concise technical
850specification of the feature and a rationale for the feature.
851
852We intend PEPs to be the primary mechanisms for proposing new
853features, for collecting community input on an issue, and for
854documenting the design decisions that have gone into Python. The PEP
855author is responsible for building consensus within the community and
856documenting dissenting opinions.
857
858The PEPs are available at http://python.sourceforge.net/peps/.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000859
860Augmented Assignment
861--------------------
862
863This must have been the most-requested feature of the past years!
864Eleven new assignment operators were added:
865
Guido van Rossume905e952000-09-05 12:42:46 +0000866 += -= *= /= %= **= <<= >>= &= ^= |=
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000867
868For example,
869
870 A += B
871
872is similar to
873
874 A = A + B
875
876except that A is evaluated only once (relevant when A is something
877like dict[index].attr).
878
879However, if A is a mutable object, A may be modified in place. Thus,
880if A is a number or a string, A += B has the same effect as A = A+B
881(except A is only evaluated once); but if a is a list, A += B has the
882same effect as A.extend(B)!
883
884Classes and built-in object types can override the new operators in
885order to implement the in-place behavior; the not-in-place behavior is
886used automatically as a fallback when an object doesn't implement the
887in-place behavior. For classes, the method name is derived from the
888method name for the corresponding not-in-place operator by inserting
889an 'i' in front of the name, e.g. __iadd__ implements in-place
890__add__.
891
892Augmented assignment was implemented by Thomas Wouters.
893
894
895List Comprehensions
896-------------------
897
898This is a flexible new notation for lists whose elements are computed
899from another list (or lists). The simplest form is:
900
901 [<expression> for <variable> in <sequence>]
902
Guido van Rossum56db0952000-09-06 23:34:25 +0000903For example, [i**2 for i in range(4)] yields the list [0, 1, 4, 9].
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000904This is more efficient than a for loop with a list.append() call.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000905
906You can also add a condition:
907
908 [<expression> for <variable> in <sequence> if <condition>]
909
910For example, [w for w in words if w == w.lower()] would yield the list
911of words that contain no uppercase characters. This is more efficient
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000912than a for loop with an if statement and a list.append() call.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000913
914You can also have nested for loops and more than one 'if' clause. For
915example, here's a function that flattens a sequence of sequences::
916
917 def flatten(seq):
918 return [x for subseq in seq for x in subseq]
919
920 flatten([[0], [1,2,3], [4,5], [6,7,8,9], []])
921
922This prints
923
924 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
925
926List comprehensions originated as a patch set from Greg Ewing; Skip
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000927Montanaro and Thomas Wouters also contributed. Described by PEP 202.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000928
929
930Extended Import Statement
931-------------------------
932
933Many people have asked for a way to import a module under a different
934name. This can be accomplished like this:
935
936 import foo
937 bar = foo
938 del foo
939
940but this common idiom gets old quickly. A simple extension of the
941import statement now allows this to be written as follows:
942
943 import foo as bar
944
945There's also a variant for 'from ... import':
946
947 from foo import bar as spam
948
949This also works with packages; e.g. you can write this:
950
951 import test.regrtest as regrtest
952
953Note that 'as' is not a new keyword -- it is recognized only in this
954context (this is only possible because the syntax for the import
955statement doesn't involve expressions).
956
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000957Implemented by Thomas Wouters. Described by PEP 221.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000958
959
960Extended Print Statement
961------------------------
962
963Easily the most controversial new feature, this extension to the print
964statement adds an option to make the output go to a different file
965than the default sys.stdout.
966
967For example, to write an error message to sys.stderr, you can now
968write:
969
970 print >> sys.stderr, "Error: bad dog!"
971
972As a special feature, if the expression used to indicate the file
Fred Drake45888ff2000-09-29 17:09:11 +0000973evaluates to None, the current value of sys.stdout is used. Thus:
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000974
975 print >> None, "Hello world"
976
977is equivalent to
978
979 print "Hello world"
980
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000981Design and implementation by Barry Warsaw. Described by PEP 214.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000982
983
984Optional Collection of Cyclical Garbage
985---------------------------------------
986
987Python is now equipped with a garbage collector that can hunt down
988cyclical references between Python objects. It's no replacement for
989reference counting; in fact, it depends on the reference counts being
990correct, and decides that a set of objects belong to a cycle if all
991their reference counts can be accounted for from their references to
992each other. This devious scheme was first proposed by Eric Tiedemann,
993and brought to implementation by Neil Schemenauer.
994
995There's a module "gc" that lets you control some parameters of the
996garbage collection. There's also an option to the configure script
997that lets you enable or disable the garbage collection. In 2.0b1,
998it's on by default, so that we (hopefully) can collect decent user
999experience with this new feature. There are some questions about its
Fred Drake9f11cf82000-09-29 17:54:40 +00001000performance. If it proves to be too much of a problem, we'll turn it
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001001off by default in the final 2.0 release.
1002
1003
1004Smaller Changes
1005---------------
1006
1007A new function zip() was added. zip(seq1, seq2, ...) is equivalent to
1008map(None, seq1, seq2, ...) when the sequences have the same length;
1009i.e. zip([1,2,3], [10,20,30]) returns [(1,10), (2,20), (3,30)]. When
1010the lists are not all the same length, the shortest list wins:
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001011zip([1,2,3], [10,20]) returns [(1,10), (2,20)]. See PEP 201.
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001012
1013sys.version_info is a tuple (major, minor, micro, level, serial).
1014
1015Dictionaries have an odd new method, setdefault(key, default).
1016dict.setdefault(key, default) returns dict[key] if it exists; if not,
1017it sets dict[key] to default and returns that value. Thus:
1018
1019 dict.setdefault(key, []).append(item)
1020
1021does the same work as this common idiom:
1022
1023 if not dict.has_key(key):
1024 dict[key] = []
1025 dict[key].append(item)
1026
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001027There are two new variants of SyntaxError that are raised for
1028indentation-related errors: IndentationError and TabError.
1029
1030Changed \x to consume exactly two hex digits; see PEP 223. Added \U
1031escape that consumes exactly eight hex digits.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001032
1033The limits on the size of expressions and file in Python source code
1034have been raised from 2**16 to 2**32. Previous versions of Python
1035were limited because the maximum argument size the Python VM accepted
1036was 2**16. This limited the size of object constructor expressions,
1037e.g. [1,2,3] or {'a':1, 'b':2}, and the size of source files. This
1038limit was raised thanks to a patch by Charles Waldman that effectively
1039fixes the problem. It is now much more likely that you will be
1040limited by available memory than by an arbitrary limit in Python.
1041
1042The interpreter's maximum recursion depth can be modified by Python
1043programs using sys.getrecursionlimit and sys.setrecursionlimit. This
1044limit is the maximum number of recursive calls that can be made by
1045Python code. The limit exists to prevent infinite recursion from
1046overflowing the C stack and causing a core dump. The default value is
10471000. The maximum safe value for a particular platform can be found
1048by running Misc/find_recursionlimit.py.
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001049
1050New Modules and Packages
1051------------------------
1052
1053atexit - for registering functions to be called when Python exits.
1054
1055imputil - Greg Stein's alternative API for writing custom import
1056hooks.
1057
1058pyexpat - an interface to the Expat XML parser, contributed by Paul
1059Prescod.
1060
1061xml - a new package with XML support code organized (so far) in three
1062subpackages: xml.dom, xml.sax, and xml.parsers. Describing these
1063would fill a volume. There's a special feature whereby a
1064user-installed package named _xmlplus overrides the standard
1065xmlpackage; this is intended to give the XML SIG a hook to distribute
1066backwards-compatible updates to the standard xml package.
1067
1068webbrowser - a platform-independent API to launch a web browser.
1069
1070
Guido van Rossume905e952000-09-05 12:42:46 +00001071Changed Modules
1072---------------
1073
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001074array -- new methods for array objects: count, extend, index, pop, and
1075remove
1076
1077binascii -- new functions b2a_hex and a2b_hex that convert between
1078binary data and its hex representation
1079
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001080calendar -- Many new functions that support features including control
1081over which day of the week is the first day, returning strings instead
1082of printing them. Also new symbolic constants for days of week,
1083e.g. MONDAY, ..., SUNDAY.
1084
1085cgi -- FieldStorage objects have a getvalue method that works like a
1086dictionary's get method and returns the value attribute of the object.
1087
1088ConfigParser -- The parser object has new methods has_option,
1089remove_section, remove_option, set, and write. They allow the module
1090to be used for writing config files as well as reading them.
1091
1092ftplib -- ntransfercmd(), transfercmd(), and retrbinary() all now
Guido van Rossume905e952000-09-05 12:42:46 +00001093optionally support the RFC 959 REST command.
1094
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001095gzip -- readline and readlines now accept optional size arguments
Guido van Rossume905e952000-09-05 12:42:46 +00001096
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001097httplib -- New interfaces and support for HTTP/1.1 by Greg Stein. See
1098the module doc strings for details.
Guido van Rossum830ca2a2000-09-05 15:34:16 +00001099
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001100locale -- implement getdefaultlocale for Win32 and Macintosh
1101
1102marshal -- no longer dumps core when marshaling deeply nested or
1103recursive data structures
1104
1105os -- new functions isatty, seteuid, setegid, setreuid, setregid
1106
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001107os/popen2 -- popen2/popen3/popen4 support under Windows. popen2/popen3
1108support under Unix.
1109
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001110os/pty -- support for openpty and forkpty
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001111
1112os.path -- fix semantics of os.path.commonprefix
1113
1114smtplib -- support for sending very long messages
1115
1116socket -- new function getfqdn()
1117
1118readline -- new functions to read, write and truncate history files.
1119The readline section of the library reference manual contains an
1120example.
1121
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001122select -- add interface to poll system call
1123
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001124shutil -- new copyfileobj function
1125
1126SimpleHTTPServer, CGIHTTPServer -- Fix problems with buffering in the
1127HTTP server.
1128
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001129Tkinter -- optimization of function flatten
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001130
1131urllib -- scans environment variables for proxy configuration,
Tim Peters8b092332000-09-05 20:15:25 +00001132e.g. http_proxy.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001133
1134whichdb -- recognizes dumbdbm format
Guido van Rossume905e952000-09-05 12:42:46 +00001135
1136
1137Obsolete Modules
1138----------------
1139
1140None. However note that 1.6 made a whole slew of modules obsolete:
1141stdwin, soundex, cml, cmpcache, dircache, dump, find, grep, packmail,
1142poly, zmod, strop, util, whatsound.
1143
1144
1145Changed, New, Obsolete Tools
1146----------------------------
1147
Tim Peters8b092332000-09-05 20:15:25 +00001148None.
Guido van Rossume905e952000-09-05 12:42:46 +00001149
1150
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001151C-level Changes
1152---------------
1153
1154Several cleanup jobs were carried out throughout the source code.
1155
1156All C code was converted to ANSI C; we got rid of all uses of the
1157Py_PROTO() macro, which makes the header files a lot more readable.
1158
1159Most of the portability hacks were moved to a new header file,
1160pyport.h; several other new header files were added and some old
1161header files were removed, in an attempt to create a more rational set
1162of header files. (Few of these ever need to be included explicitly;
1163they are all included by Python.h.)
1164
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001165Trent Mick ensured portability to 64-bit platforms, under both Linux
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001166and Win64, especially for the new Intel Itanium processor. Mick also
1167added large file support for Linux64 and Win64.
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001168
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001169The C APIs to return an object's size have been update to consistently
1170use the form PyXXX_Size, e.g. PySequence_Size and PyDict_Size. In
1171previous versions, the abstract interfaces used PyXXX_Length and the
1172concrete interfaces used PyXXX_Size. The old names,
1173e.g. PyObject_Length, are still available for backwards compatibility
1174at the API level, but are deprecated.
1175
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001176The PyOS_CheckStack function has been implemented on Windows by
1177Fredrik Lundh. It prevents Python from failing with a stack overflow
1178on Windows.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001179
1180The GC changes resulted in creation of two new slots on object,
1181tp_traverse and tp_clear. The augmented assignment changes result in
Guido van Rossum4338a282000-09-06 13:02:08 +00001182the creation of a new slot for each in-place operator.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001183
1184The GC API creates new requirements for container types implemented in
Guido van Rossum4338a282000-09-06 13:02:08 +00001185C extension modules. See Include/objimpl.h for details.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001186
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001187PyErr_Format has been updated to automatically calculate the size of
1188the buffer needed to hold the formatted result string. This change
1189prevents crashes caused by programmer error.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001190
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001191New C API calls: PyObject_AsFileDescriptor, PyErr_WriteUnraisable.
Guido van Rossume905e952000-09-05 12:42:46 +00001192
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001193PyRun_AnyFileEx, PyRun_SimpleFileEx, PyRun_FileEx -- New functions
1194that are the same as their non-Ex counterparts except they take an
1195extra flag argument that tells them to close the file when done.
1196
1197XXX There were other API changes that should be fleshed out here.
Guido van Rossumab9d6f01998-08-10 22:01:13 +00001198
Tim Peters8b092332000-09-05 20:15:25 +00001199
1200Windows Changes
1201---------------
1202
1203New popen2/popen3/peopen4 in os module (see Changed Modules above).
1204
1205os.popen is much more usable on Windows 95 and 98. See Microsoft
1206Knowledge Base article Q150956. The Win9x workaround described there
1207is implemented by the new w9xpopen.exe helper in the root of your
1208Python installation. Note that Python uses this internally; it is not
1209a standalone program.
1210
1211Administrator privileges are no longer required to install Python
1212on Windows NT or Windows 2000. If you have administrator privileges,
1213Python's registry info will be written under HKEY_LOCAL_MACHINE.
1214Otherwise the installer backs off to writing Python's registry info
Guido van Rossum4338a282000-09-06 13:02:08 +00001215under HKEY_CURRENT_USER. The latter is sufficient for all "normal"
Tim Peters8b092332000-09-05 20:15:25 +00001216uses of Python, but will prevent some advanced uses from working
1217(for example, running a Python script as an NT service, or possibly
1218from CGI).
1219
1220[This was new in 1.6] The installer no longer runs a separate Tcl/Tk
1221installer; instead, it installs the needed Tcl/Tk files directly in the
1222Python directory. If you already have a Tcl/Tk installation, this
1223wastes some disk space (about 4 Megs) but avoids problems with
1224conflicting Tcl/Tk installations, and makes it much easier for Python
1225to ensure that Tcl/Tk can find all its files.
1226
1227[This was new in 1.6] The Windows installer now installs by default in
1228\Python20\ on the default volume, instead of \Program Files\Python-2.0\.
1229
Guido van Rossumf62ed9c2000-09-26 11:16:10 +00001230
1231Updates to the changes between 1.5.2 and 1.6
1232--------------------------------------------
1233
1234The 1.6 NEWS file can't be changed after the release is done, so here
1235is some late-breaking news:
1236
1237New APIs in locale.py: normalize(), getdefaultlocale(), resetlocale(),
1238and changes to getlocale() and setlocale().
1239
1240The new module is now enabled per default.
1241
1242It is not true that the encodings codecs cannot be used for normal
1243strings: the string.encode() (which is also present on 8-bit strings
1244!) allows using them for 8-bit strings too, e.g. to convert files from
1245cp1252 (Windows) to latin-1 or vice-versa.
1246
1247Japanese codecs are available from Tamito KAJIYAMA:
1248http://pseudo.grad.sccs.chukyo-u.ac.jp/~kajiyama/python/
1249
1250
Guido van Rossumab9d6f01998-08-10 22:01:13 +00001251======================================================================