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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
Jeremy Hylton4589bd82001-02-01 20:38:45 +00006- Scopes nest. If a name is used in a function or class, but is not
7 local, the definition in the nearest enclosing function scope will
8 be used. One consequence of this change is that lambda statements
9 could reference variables in the namespaces where the lambda is
10 defined. In some unusual cases, this change will break code.
11
12 In all previous version of Python, names were resolved in exactly
13 three namespaces -- the local namespace, the global namespace, and
14 the builtin namespace. According to this old defintion, if a
15 function A is defined within a function B, the names bound in B are
16 not visible in A. The new rules make names bound in B visible in A,
17 unless A contains a name binding that hides the binding in B.
18
19 Section 4.1 of the reference manual describes the new scoping rules
20 in detail. The test script in Lib/test/test_scope.py demonstrates
21 some of the effects of the change.
22
23 The new rules will cause existing code to break if it defines nested
24 functions where an outer function has local variables with the same
25 name as globals or builtins used by the inner function. Example:
26
27 def munge(str):
28 def helper(x):
29 return str(x)
30 if type(str) != type(''):
31 str = helper(str)
32 return str.strip()
33
34 Under the old rules, the name str in helper() is bound to the
35 builtin function str(). Under the new rules, it will be bound to
36 the argument named str and an error will occur when helper() is
37 called.
38
Tim Peters40ead762001-01-27 05:35:26 +000039- repr(string) is easier to read, now using hex escapes instead of octal,
40 and using \t, \n and \r instead of \011, \012 and \015 (respectively):
41
42 >>> "\texample \r\n" + chr(0) + chr(255)
43 '\texample \r\n\x00\xff' # in 2.1
44 '\011example \015\012\000\377' # in 2.0
45
Moshe Zadka6af0ce02001-01-29 06:41:00 +000046- Functions are now compared and hashed by identity, not by value, since
47 the func_code attribute is writable.
48
Jeremy Hylton4589bd82001-02-01 20:38:45 +000049- The compiler will report a SyntaxError if "from ... import *" occurs
50 in a function or class scope. The language reference has documented
51 that this case is illegal, but the compiler never checked for it.
52 The recent introduction of nested scope makes the meaning of this
53 form of name binding ambiguous.
54
Fred Drakefb9d7122001-02-01 20:00:40 +000055- Weak references (PEP 205) have been added. This involves a few
56 changes in the core, an extension module (_weakref), and a Python
57 module (weakref). The weakref module is the public interface. It
58 includes support for "explicit" weak references, proxy objects, and
59 mappings with weakly held values.
60
Jeremy Hylton0072d5a2001-02-01 22:53:15 +000061- A 'continue' statement can now appear in a try block within the body
62 of a loop. It is still not possible to use continue in a finally
63 clause.
64
Tim Petersd7b5e882001-01-25 03:36:26 +000065Standard library
66
Barry Warsaw30dbd142001-01-31 22:14:01 +000067- mailbox.py now has a new class, PortableUnixMailbox which is
68 identical to UnixMailbox but uses a more portable scheme for
69 determining From_ separators. Also, the constructors for all the
70 classes in this module have a new optional `factory' argument, which
71 is a callable used when new message classes must be instantiated by
72 the next() method.
73
Tim Petersd7b5e882001-01-25 03:36:26 +000074- random.py is now self-contained, and offers all the functionality of
75 the now-deprecated whrandom.py. See the docs for details. random.py
76 also supports new functions getstate() and setstate(), for saving
Tim Petersd52269b2001-01-25 06:23:18 +000077 and restoring the internal state of the generator; and jumpahead(n),
78 for quickly forcing the internal state to be the same as if n calls to
79 random() had been made. The latter is particularly useful for multi-
80 threaded programs, creating one instance of the random.Random() class for
81 each thread, then using .jumpahead() to force each instance to use a
82 non-overlapping segment of the full period.
Tim Petersd7b5e882001-01-25 03:36:26 +000083
Tim Peters0de88fc2001-02-01 04:59:18 +000084- random.py's seed() function is new. For bit-for-bit compatibility with
85 prior releases, use the whseed function instead. The new seed function
86 addresses two problems: (1) The old function couldn't produce more than
87 about 2**24 distinct internal states; the new one about 2**45 (the best
88 that can be done in the Wichmann-Hill generator). (2) The old function
89 sometimes produced identical internal states when passed distinct
90 integers, and there was no simple way to predict when that would happen;
91 the new one guarantees to produce distinct internal states for all
92 arguments in [0, 27814431486576L).
93
Jeremy Hylton4c4fda02001-02-02 03:29:24 +000094- The socket module now supports raw packets on Linux. The socket
95 family is AF_PACKET.
96
Tim Petersee826f82001-01-31 19:39:44 +000097Windows changes
98
99- Build procedure: the zlib project is built in a different way that
100 ensures the zlib header files used can no longer get out of synch with
101 the zlib binary used. See PCbuild\readme.txt for details.
102
Tim Petersd7b5e882001-01-25 03:36:26 +0000103
Tim Petersa3a3a032000-11-30 05:22:44 +0000104What's New in Python 2.1 alpha 1?
105=================================
106
107Core language, builtins, and interpreter
108
Marc-André Lemburgebb195b2001-01-20 10:34:52 +0000109- There is a new Unicode companion to the PyObject_Str() API
110 called PyObject_Unicode(). It behaves in the same way as the
111 former, but assures that the returned value is an Unicode object
112 (applying the usual coercion if necessary).
Marc-André Lemburgad7c98e2001-01-17 17:09:53 +0000113
Guido van Rossumf98eda02001-01-17 15:54:45 +0000114- The comparison operators support "rich comparison overloading" (PEP
115 207). C extension types can provide a rich comparison function in
116 the new tp_richcompare slot in the type object. The cmp() function
117 and the C function PyObject_Compare() first try the new rich
118 comparison operators before trying the old 3-way comparison. There
119 is also a new C API PyObject_RichCompare() (which also falls back on
120 the old 3-way comparison, but does not constrain the outcome of the
121 rich comparison to a Boolean result).
122
123 The rich comparison function takes two objects (at least one of
124 which is guaranteed to have the type that provided the function) and
125 an integer indicating the opcode, which can be Py_LT, Py_LE, Py_EQ,
126 Py_NE, Py_GT, Py_GE (for <, <=, ==, !=, >, >=), and returns a Python
127 object, which may be NotImplemented (in which case the tp_compare
128 slot function is used as a fallback, if defined).
129
130 Classes can overload individual comparison operators by defining one
131 or more of the methods__lt__, __le__, __eq__, __ne__, __gt__,
Guido van Rossuma88479f2001-01-18 14:28:08 +0000132 __ge__. There are no explicit "reflected argument" versions of
133 these; instead, __lt__ and __gt__ are each other's reflection,
134 likewise for__le__ and __ge__; __eq__ and __ne__ are their own
135 reflection (similar at the C level). No other implications are
136 made; in particular, Python does not assume that == is the Boolean
137 inverse of !=, or that < is the Boolean inverse of >=. This makes
138 it possible to define types with partial orderings.
Guido van Rossumf98eda02001-01-17 15:54:45 +0000139
140 Classes or types that want to implement (in)equality tests but not
141 the ordering operators (i.e. unordered types) should implement ==
142 and !=, and raise an error for the ordering operators.
143
Guido van Rossuma88479f2001-01-18 14:28:08 +0000144 It is possible to define types whose rich comparison results are not
Guido van Rossumf98eda02001-01-17 15:54:45 +0000145 Boolean; e.g. a matrix type might want to return a matrix of bits
146 for A < B, giving elementwise comparisons. Such types should ensure
147 that any interpretation of their value in a Boolean context raises
148 an exception, e.g. by defining __nonzero__ (or the tp_nonzero slot
149 at the C level) to always raise an exception.
150
Guido van Rossuma88479f2001-01-18 14:28:08 +0000151- Complex numbers use rich comparisons to define == and != but raise
152 an exception for <, <=, > and >=. Unfortunately, this also means
153 that cmp() of two complex numbers raises an exception when the two
154 numbers differ. Since it is not mathematically meaningful to compare
155 complex numbers except for equality, I hope that this doesn't break
156 too much code.
157
Barry Warsaw573b5412001-01-15 20:43:18 +0000158- Functions and methods now support getting and setting arbitrarily
159 named attributes (PEP 232). Functions have a new __dict__
160 (a.k.a. func_dict) which hold the function attributes. Methods get
161 and set attributes on their underlying im_func. It is a TypeError
162 to set an attribute on a bound method.
163
Guido van Rossum051e3352001-01-15 19:11:10 +0000164- The xrange() object implementation has been improved so that
165 xrange(sys.maxint) can be used on 64-bit platforms. There's still a
166 limitation that in this case len(xrange(sys.maxint)) can't be
167 calculated, but the common idiom "for i in xrange(sys.maxint)" will
168 work fine as long as the index i doesn't actually reach 2**31.
169 (Python uses regular ints for sequence and string indices; fixing
170 that is much more work.)
171
Guido van Rossum1cc8f832001-01-12 16:25:08 +0000172- Two changes to from...import:
173
174 1) "from M import X" now works even if M is not a real module; it's
175 basically a getattr() operation with AttributeError exceptions
176 changed into ImportError.
177
178 2) "from M import *" now looks for M.__all__ to decide which names to
179 import; if M.__all__ doesn't exist, it uses M.__dict__.keys() but
180 filters out names starting with '_' as before. Whether or not
181 __all__ exists, there's no restriction on the type of M.
182
Guido van Rossumf61f1662001-01-10 20:13:55 +0000183- File objects have a new method, xreadlines(). This is the fastest
184 way to iterate over all lines in a file:
185
186 for line in file.xreadlines():
187 ...do something to line...
188
189 See the xreadlines module (mentioned below) for how to do this for
190 other file-like objects.
191
192- Even if you don't use file.xreadlines(), you may expect a speedup on
193 line-by-line input. The file.readline() method has been optimized
Tim Petersf29b64d2001-01-15 06:33:19 +0000194 quite a bit in platform-specific ways: on systems (like Linux) that
195 support flockfile(), getc_unlocked(), and funlockfile(), those are
196 used by default. On systems (like Windows) without getc_unlocked(),
197 a complicated (but still thread-safe) method using fgets() is used by
198 default.
199
Tim Petersd52269b2001-01-25 06:23:18 +0000200 You can force use of the fgets() method by #define'ing
201 USE_FGETS_IN_GETLINE at build time (it may be faster than
Tim Petersf29b64d2001-01-15 06:33:19 +0000202 getc_unlocked()).
203
Tim Petersd52269b2001-01-25 06:23:18 +0000204 You can force fgets() not to be used by #define'ing
205 DONT_USE_FGETS_IN_GETLINE (this is the first thing to try if std test
Tim Petersf29b64d2001-01-15 06:33:19 +0000206 test_bufio.py fails -- and let us know if it does!).
207
208- In addition, the fileinput module, while still slower than the other
209 methods on most platforms, has been sped up too, by using
210 file.readlines(sizehint).
Guido van Rossumf61f1662001-01-10 20:13:55 +0000211
212- Support for run-time warnings has been added, including a new
213 command line option (-W) to specify the disposition of warnings.
214 See the description of the warnings module below.
215
216- Extensive changes have been made to the coercion code. This mostly
217 affects extension modules (which can now implement mixed-type
218 numerical operators without having to use coercion), but
219 occasionally, in boundary cases the coercion semantics have changed
220 subtly. Since this was a terrible gray area of the language, this
Guido van Rossumae72d872001-01-11 15:00:14 +0000221 is considered an improvement. Also note that __rcmp__ is no longer
Guido van Rossumf61f1662001-01-10 20:13:55 +0000222 supported -- instead of calling __rcmp__, __cmp__ is called with
Guido van Rossuma88479f2001-01-18 14:28:08 +0000223 reflected arguments.
Guido van Rossumf61f1662001-01-10 20:13:55 +0000224
Guido van Rossumf98eda02001-01-17 15:54:45 +0000225- In connection with the coercion changes, a new built-in singleton
226 object, NotImplemented is defined. This can be returned for
227 operations that wish to indicate they are not implemented for a
228 particular combination of arguments. From C, this is
229 Py_NotImplemented.
230
Martin v. Löwisbe4c0f52001-01-04 20:30:56 +0000231- The interpreter accepts now bytecode files on the command line even
232 if they do not have a .pyc or .pyo extension. On Linux, after executing
233
234 echo ':pyc:M::\x87\xc6\x0d\x0a::/usr/local/bin/python:' > /proc/sys/fs/binfmt_misc/register
235
236 any byte code file can be used as an executable (i.e. as an argument
237 to execve(2)).
238
Tim Peters9940b802000-12-01 07:59:35 +0000239- %[xXo] formats of negative Python longs now produce a sign
Tim Petersa3a3a032000-11-30 05:22:44 +0000240 character. In 1.6 and earlier, they never produced a sign,
241 and raised an error if the value of the long was too large
242 to fit in a Python int. In 2.0, they produced a sign if and
243 only if too large to fit in an int. This was inconsistent
244 across platforms (because the size of an int varies across
245 platforms), and inconsistent with hex() and oct(). Example:
246
247 >>> "%x" % -0x42L
Tim Peters9940b802000-12-01 07:59:35 +0000248 '-42' # in 2.1
Tim Petersa3a3a032000-11-30 05:22:44 +0000249 'ffffffbe' # in 2.0 and before, on 32-bit machines
250 >>> hex(-0x42L)
251 '-0x42L' # in all versions of Python
252
Tim Peters9940b802000-12-01 07:59:35 +0000253 The behavior of %d formats for negative Python longs remains
254 the same as in 2.0 (although in 1.6 and before, they raised
255 an error if the long didn't fit in a Python int).
256
257 %u formats don't make sense for Python longs, but are allowed
258 and treated the same as %d in 2.1. In 2.0, a negative long
259 formatted via %u produced a sign if and only if too large to
260 fit in an int. In 1.6 and earlier, a negative long formatted
261 via %u raised an error if it was too big to fit in an int.
262
Guido van Rossum3661d392000-12-12 22:10:31 +0000263- Dictionary objects have an odd new method, popitem(). This removes
264 an arbitrary item from the dictionary and returns it (in the form of
265 a (key, value) pair). This can be useful for algorithms that use a
266 dictionary as a bag of "to do" items and repeatedly need to pick one
267 item. Such algorithms normally end up running in quadratic time;
268 using popitem() they can usually be made to run in linear time.
269
Tim Peters36cdad12000-12-29 02:06:45 +0000270Standard library
271
Thomas Woutersfe385252001-01-19 23:16:56 +0000272- In the time module, the time argument to the functions strftime,
273 localtime, gmtime, asctime and ctime is now optional, defaulting to
274 the current time (in the local timezone).
275
Guido van Rossumda91f222001-01-15 16:36:08 +0000276- The ftplib module now defaults to passive mode, which is deemed a
277 more useful default given that clients are often inside firewalls
278 these days. Note that this could break if ftplib is used to connect
279 to a *server* that is inside a firewall, from outside; this is
280 expected to be a very rare situation. To fix that, you can call
281 ftp.set_pasv(0).
282
Martin v. Löwis10a27872001-01-13 09:54:41 +0000283- The module site now treats .pth files not only for path configuration,
284 but also supports extensions to the initialization code: Lines starting
285 with import are executed.
286
Guido van Rossumf61f1662001-01-10 20:13:55 +0000287- There's a new module, warnings, which implements a mechanism for
288 issuing and filtering warnings. There are some new built-in
289 exceptions that serve as warning categories, and a new command line
290 option, -W, to control warnings (e.g. -Wi ignores all warnings, -We
291 turns warnings into errors). warnings.warn(message[, category])
292 issues a warning message; this can also be called from C as
293 PyErr_Warn(category, message).
294
295- A new module xreadlines was added. This exports a single factory
296 function, xreadlines(). The intention is that this code is the
297 absolutely fastest way to iterate over all lines in an open
298 file(-like) object:
299
300 import xreadlines
301 for line in xreadlines.xreadlines(file):
302 ...do something to line...
303
304 This is equivalent to the previous the speed record holder using
305 file.readlines(sizehint). Note that if file is a real file object
306 (as opposed to a file-like object), this is equivalent:
307
308 for line in file.xreadlines():
309 ...do something to line...
310
Tim Peters36cdad12000-12-29 02:06:45 +0000311- The bisect module has new functions bisect_left, insort_left,
312 bisect_right and insort_right. The old names bisect and insort
313 are now aliases for bisect_right and insort_right. XXX_right
314 and XXX_left methods differ in what happens when the new element
315 compares equal to one or more elements already in the list: the
316 XXX_left methods insert to the left, the XXX_right methods to the
Tim Peters742bb6f2001-01-05 08:05:32 +0000317 right. Code that doesn't care where equal elements end up should
318 continue to use the old, short names ("bisect" and "insort").
Tim Peters36cdad12000-12-29 02:06:45 +0000319
Andrew M. Kuchlingf6f3a892001-01-13 14:53:34 +0000320- The new curses.panel module wraps the panel library that forms part
321 of SYSV curses and ncurses. Contributed by Thomas Gellekum.
322
Guido van Rossumf61f1662001-01-10 20:13:55 +0000323- The SocketServer module now sets the allow_reuse_address flag by
324 default in the TCPServer class.
325
326- A new function, sys._getframe(), returns the stack frame pointer of
327 the caller. This is intended only as a building block for
328 higher-level mechanisms such as string interpolation.
329
330Build issues
331
Guido van Rossum1e33bdc2001-01-23 03:17:00 +0000332- For Unix (and Unix-compatible) builds, configuration and building of
333 extension modules is now greatly automated. Rather than having to
334 edit the Modules/Setup file to indicate which modules should be
335 built and where their include files and libraries are, a
336 distutils-based setup.py script now takes care of building most
337 extension modules. All extension modules built this way are built
338 as shared libraries. Only a few modules that must be linked
339 statically are still listed in the Setup file; you won't need to
340 edit their configuration.
341
342- Python should now build out of the box on Cygwin. If it doesn't,
343 mail to Jason Tishler (jlt63 at users.sourceforge.net).
Guido van Rossumf61f1662001-01-10 20:13:55 +0000344
345- Python now always uses its own (renamed) implementation of getopt()
346 -- there's too much variation among C library getopt()
347 implementations.
348
349- C++ compilers are better supported; the CXX macro is always set to a
350 C++ compiler if one is found.
Tim Peters36cdad12000-12-29 02:06:45 +0000351
Tim Petersd92dfe02000-12-12 01:18:41 +0000352Windows changes
353
354- select module: By default under Windows, a select() call
355 can specify no more than 64 sockets. Python now boosts
356 this Microsoft default to 512. If you need even more than
357 that, see the MS docs (you'll need to #define FD_SETSIZE
358 and recompile Python from source).
359
Guido van Rossumf61f1662001-01-10 20:13:55 +0000360- Support for Windows 3.1, DOS and OS/2 is gone. The Lib/dos-8x3
361 subdirectory is no more!
362
Tim Petersa3a3a032000-11-30 05:22:44 +0000363
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000364What's New in Python 2.0?
Fred Drake1a640502000-10-16 20:27:25 +0000365=========================
Guido van Rossum61000331997-08-15 04:39:58 +0000366
Guido van Rossum8ed602b2000-09-01 22:34:33 +0000367Below is a list of all relevant changes since release 1.6. Older
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000368changes are in the file HISTORY. If you are making the jump directly
369from Python 1.5.2 to 2.0, make sure to read the section for 1.6 in the
370HISTORY file! Many important changes listed there.
Guido van Rossum61000331997-08-15 04:39:58 +0000371
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000372Alternatively, a good overview of the changes between 1.5.2 and 2.0 is
373the document "What's New in Python 2.0" by Kuchling and Moshe Zadka:
374http://starship.python.net/crew/amk/python/writing/new-python/.
Guido van Rossum1f83cce1997-10-06 21:04:35 +0000375
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000376--Guido van Rossum (home page: http://www.pythonlabs.com/~guido/)
Guido van Rossum437cfe81999-04-08 20:17:57 +0000377
378======================================================================
379
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000380What's new in 2.0 (since release candidate 1)?
381==============================================
382
383Standard library
384
385- The copy_reg module was modified to clarify its intended use: to
386 register pickle support for extension types, not for classes.
387 pickle() will raise a TypeError if it is passed a class.
388
389- Fixed a bug in gettext's "normalize and expand" code that prevented
390 it from finding an existing .mo file.
391
392- Restored support for HTTP/0.9 servers in httplib.
393
Tim Peters989b7b92000-10-16 20:24:53 +0000394- The math module was changed to stop raising OverflowError in case of
395 underflow, and return 0 instead in underflow cases. Whether Python
396 used to raise OverflowError in case of underflow was platform-
397 dependent (it did when the platform math library set errno to ERANGE
398 on underflow).
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000399
400- Fixed a bug in StringIO that occurred when the file position was not
401 at the end of the file and write() was called with enough data to
402 extend past the end of the file.
403
404- Fixed a bug that caused Tkinter error messages to get lost on
405 Windows. The bug was fixed by replacing direct use of
406 interp->result with Tcl_GetStringResult(interp).
407
408- Fixed bug in urllib2 that caused it to fail when it received an HTTP
409 redirect response.
410
411- Several changes were made to distutils: Some debugging code was
412 removed from util. Fixed the installer used when an external zip
413 program (like WinZip) is not found; the source code for this
414 installer is in Misc/distutils. check_lib() was modified to behave
415 more like AC_CHECK_LIB by add other_libraries() as a parameter. The
416 test for whether installed modules are on sys.path was changed to
417 use both normcase() and normpath().
418
Jeremy Hyltond867a2c2000-10-16 20:41:38 +0000419- Several minor bugs were fixed in the xml package (the minidom,
420 pulldom, expatreader, and saxutils modules).
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000421
422- The regression test driver (regrtest.py) behavior when invoked with
423 -l changed: It now reports a count of objects that are recognized as
424 garbage but not freed by the garbage collector.
425
Tim Peters989b7b92000-10-16 20:24:53 +0000426- The regression test for the math module was changed to test
427 exceptional behavior when the test is run in verbose mode. Python
428 cannot yet guarantee consistent exception behavior across platforms,
429 so the exception part of test_math is run only in verbose mode, and
430 may fail on your platform.
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000431
432Internals
433
434- PyOS_CheckStack() has been disabled on Win64, where it caused
435 test_sre to fail.
436
437Build issues
438
439- Changed compiler flags, so that gcc is always invoked with -Wall and
440 -Wstrict-prototypes. Users compiling Python with GCC should see
441 exactly one warning, except if they have passed configure the
Tim Peters989b7b92000-10-16 20:24:53 +0000442 --with-pydebug flag. The expected warning is for getopt() in
Tim Petersadfb94f2000-10-16 20:51:33 +0000443 Modules/main.c. This warning will be fixed for Python 2.1.
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000444
Tim Petersa3a3a032000-11-30 05:22:44 +0000445- Fixed configure to add -threads argument during linking on OSF1.
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000446
447Tools and other miscellany
448
449- The compiler in Tools/compiler was updated to support the new
450 language features introduced in 2.0: extended print statement, list
451 comprehensions, and augmented assignments. The new compiler should
452 also be backwards compatible with Python 1.5.2; the compiler will
453 always generate code for the version of the interpreter it runs
Tim Petersa3a3a032000-11-30 05:22:44 +0000454 under.
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000455
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000456What's new in 2.0 release candidate 1 (since beta 2)?
457=====================================================
458
Jeremy Hylton6040aaa2000-10-09 21:27:22 +0000459What is release candidate 1?
460
461We believe that release candidate 1 will fix all known bugs that we
462intend to fix for the 2.0 final release. This release should be a bit
463more stable than the previous betas. We would like to see even more
464widespread testing before the final release, so we are producing this
465release candidate. The final release will be exactly the same unless
466any show-stopping (or brown bag) bugs are found by testers of the
467release candidate.
468
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000469All the changes since the last beta release are bug fixes or changes
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000470to support building Python for specific platforms.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000471
472Core language, builtins, and interpreter
473
474- A bug that caused crashes when __coerce__ was used with augmented
475 assignment, e.g. +=, was fixed.
476
477- Raise ZeroDivisionError when raising zero to a negative number,
478 e.g. 0.0 ** -2.0. Note that math.pow is unrelated to the builtin
479 power operator and the result of math.pow(0.0, -2.0) will vary by
480 platform. On Linux, it raises a ValueError.
481
482- A bug in Unicode string interpolation was fixed that occasionally
483 caused errors with formats including "%%". For example, the
484 following expression "%% %s" % u"abc" no longer raises a TypeError.
485
486- Compilation of deeply nested expressions raises MemoryError instead
487 of SyntaxError, e.g. eval("[" * 50 + "]" * 50).
488
489- In 2.0b2 on Windows, the interpreter wrote .pyc files in text mode,
490 rendering them useless. They are now written in binary mode again.
491
492Standard library
493
494- Keyword arguments are now accepted for most pattern and match object
495 methods in SRE, the standard regular expression engine.
496
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000497- In SRE, fixed error with negative lookahead and lookbehind that
Jeremy Hylton32e20ff2000-10-09 19:48:11 +0000498 manifested itself as a runtime error in patterns like "(?<!abc)(def)".
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000499
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000500- Several bugs in the Unicode handling and error handling in _tkinter
501 were fixed.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000502
503- Fix memory management errors in Merge() and Tkapp_Call() routines.
504
505- Several changes were made to cStringIO to make it compatible with
506 the file-like object interface and with StringIO. If operations are
507 performed on a closed object, an exception is raised. The truncate
508 method now accepts a position argument and readline accepts a size
Tim Petersa3a3a032000-11-30 05:22:44 +0000509 argument.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000510
511- There were many changes made to the linuxaudiodev module and its
512 test suite; as a result, a short, unexpected audio sample should now
Tim Petersa3a3a032000-11-30 05:22:44 +0000513 play when the regression test is run.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000514
515 Note that this module is named poorly, because it should work
516 correctly on any platform that supports the Open Sound System
Tim Petersa3a3a032000-11-30 05:22:44 +0000517 (OSS).
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000518
519 The module now raises exceptions when errors occur instead of
520 crashing. It also defines the AFMT_A_LAW format (logarithmic A-law
521 audio) and defines a getptr() method that calls the
522 SNDCTL_DSP_GETxPTR ioctl defined in the OSS Programmer's Guide.
523
524- The library_version attribute, introduced in an earlier beta, was
525 removed because it can not be supported with early versions of the C
526 readline library, which provides no way to determine the version at
527 compile-time.
528
529- The binascii module is now enabled on Win64.
530
Tim Peters46446d62000-10-09 21:19:31 +0000531- tokenize.py no longer suffers "recursion depth" errors when parsing
532 programs with very long string literals.
533
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000534Internals
535
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000536- Fixed several buffer overflow vulnerabilities in calculate_path(),
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000537 which is called when the interpreter starts up to determine where
538 the standard library is installed. These vulnerabilities affect all
539 previous versions of Python and can be exploited by setting very
540 long values for PYTHONHOME or argv[0]. The risk is greatest for a
541 setuid Python script, although use of the wrapper in
542 Misc/setuid-prog.c will eliminate the vulnerability.
543
544- Fixed garbage collection bugs in instance creation that were
545 triggered when errors occurred during initialization. The solution,
546 applied in cPickle and in PyInstance_New(), is to call
547 PyObject_GC_Init() after the initialization of the object's
548 container attributes is complete.
549
550- pyexpat adds definitions of PyModule_AddStringConstant and
551 PyModule_AddObject if the Python version is less than 2.0, which
552 provides compatibility with PyXML on Python 1.5.2.
553
554- If the platform has a bogus definition for LONG_BIT (the number of
555 bits in a long), an error will be reported at compile time.
556
557- Fix bugs in _PyTuple_Resize() which caused hard-to-interpret garbage
558 collection crashes and possibly other, unreported crashes.
559
560- Fixed a memory leak in _PyUnicode_Fini().
561
562Build issues
563
564- configure now accepts a --with-suffix option that specifies the
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000565 executable suffix. This is useful for builds on Cygwin and Mac OS
Tim Petersa3a3a032000-11-30 05:22:44 +0000566 X, for example.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000567
568- The mmap.PAGESIZE constant is now initialized using sysconf when
569 possible, which eliminates a dependency on -lucb for Reliant UNIX.
570
571- The md5 file should now compile on all platforms.
572
573- The select module now compiles on platforms that do not define
574 POLLRDNORM and related constants.
575
576- Darwin (Mac OS X): Initial support for static builds on this
Tim Petersa3a3a032000-11-30 05:22:44 +0000577 platform.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000578
Jeremy Hylton10921202000-10-09 18:34:12 +0000579- BeOS: A number of changes were made to the build and installation
580 process. ar-fake now operates on a directory of object files.
581 dl_export.h is gone, and its macros now appear on the mwcc command
582 line during build on PPC BeOS.
583
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000584- Platform directory in lib/python2.0 is "plat-beos5" (or
Jeremy Hylton10921202000-10-09 18:34:12 +0000585 "plat-beos4", if building on BeOS 4.5), rather than "plat-beos".
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000586
587- Cygwin: Support for shared libraries, Tkinter, and sockets.
588
589- SunOS 4.1.4_JL: Fix test for directory existence in configure.
590
591Tools and other miscellany
592
593- Removed debugging prints from main used with freeze.
594
Tim Peters46446d62000-10-09 21:19:31 +0000595- IDLE auto-indent no longer crashes when it encounters Unicode
596 characters.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000597
598What's new in 2.0 beta 2 (since beta 1)?
599========================================
600
601Core language, builtins, and interpreter
602
Tim Peters482c0212000-09-26 06:33:09 +0000603- Add support for unbounded ints in %d,i,u,x,X,o formats; for example
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000604 "%d" % 2L**64 == "18446744073709551616".
Jeremy Hylton1b618592000-09-26 05:32:36 +0000605
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000606- Add -h and -V command line options to print the usage message and
607 Python version number and exit immediately.
608
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000609- eval() and exec accept Unicode objects as code parameters.
610
611- getattr() and setattr() now also accept Unicode objects for the
612 attribute name, which are converted to strings using the default
613 encoding before lookup.
614
615- Multiplication on string and Unicode now does proper bounds
616 checking; e.g. 'a' * 65536 * 65536 will raise ValueError, "repeated
617 string is too long."
618
619- Better error message when continue is found in try statement in a
Tim Petersa3a3a032000-11-30 05:22:44 +0000620 loop.
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000621
Jeremy Hylton1b618592000-09-26 05:32:36 +0000622
623Standard library and extensions
624
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000625- array: reverse() method of array now works. buffer_info() now does
Jeremy Hylton1b618592000-09-26 05:32:36 +0000626 argument checking; it still takes no arguments.
627
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000628- asyncore/asynchat: Included most recent version from Sam Rushing.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000629
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000630- cgi: Accept '&' or ';' as separator characters when parsing form data.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000631
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000632- CGIHTTPServer: Now works on Windows (and perhaps even Mac).
Jeremy Hylton1b618592000-09-26 05:32:36 +0000633
634- ConfigParser: When reading the file, options spelled in upper case
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000635 letters are now correctly converted to lowercase.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000636
637- copy: Copy Unicode objects atomically.
638
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000639- cPickle: Fail gracefully when copy_reg can't be imported.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000640
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000641- cStringIO: Implemented readlines() method.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000642
Fred Drake67233bc2000-09-26 16:40:27 +0000643- dbm: Add get() and setdefault() methods to dbm object. Add constant
644 `library' to module that names the library used. Added doc strings
645 and method names to error messages. Uses configure to determine
646 which ndbm.h file to include; Berkeley DB's nbdm and GDBM's ndbm is
647 now available options.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000648
649- distutils: Update to version 0.9.3.
650
651- dl: Add several dl.RTLD_ constants.
652
653- fpectl: Now supported on FreeBSD.
654
655- gc: Add DEBUG_SAVEALL option. When enabled all garbage objects
656 found by the collector will be saved in gc.garbage. This is useful
657 for debugging a program that creates reference cycles.
658
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000659- httplib: Three changes: Restore support for set_debuglevel feature
Jeremy Hylton1b618592000-09-26 05:32:36 +0000660 of HTTP class. Do not close socket on zero-length response. Do not
661 crash when server sends invalid content-length header.
662
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000663- mailbox: Mailbox class conforms better to qmail specifications.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000664
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000665- marshal: When reading a short, sign-extend on platforms where shorts
666 are bigger than 16 bits. When reading a long, repair the unportable
667 sign extension that was being done for 64-bit machines. (It assumed
668 that signed right shift sign-extends.)
669
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000670- operator: Add contains(), invert(), __invert__() as aliases for
671 __contains__(), inv(), and __inv__() respectively.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000672
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000673- os: Add support for popen2() and popen3() on all platforms where
674 fork() exists. (popen4() is still in the works.)
Jeremy Hylton1b618592000-09-26 05:32:36 +0000675
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000676- os: (Windows only:) Add startfile() function that acts like double-
Tim Peters482c0212000-09-26 06:33:09 +0000677 clicking on a file in Explorer (or passing the file name to the
678 DOS "start" command).
Jeremy Hylton1b618592000-09-26 05:32:36 +0000679
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000680- os.path: (Windows, DOS:) Treat trailing colon correctly in
Tim Peters482c0212000-09-26 06:33:09 +0000681 os.path.join. os.path.join("a:", "b") yields "a:b".
Jeremy Hylton1b618592000-09-26 05:32:36 +0000682
683- pickle: Now raises ValueError when an invalid pickle that contains
684 a non-string repr where a string repr was expected. This behavior
685 matches cPickle.
686
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000687- posixfile: Remove broken __del__() method.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000688
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000689- py_compile: support CR+LF line terminators in source file.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000690
691- readline: Does not immediately exit when ^C is hit when readline and
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000692 threads are configured. Adds definition of rl_library_version. (The
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000693 latter addition requires GNU readline 2.2 or later.)
Jeremy Hylton1b618592000-09-26 05:32:36 +0000694
695- rfc822: Domain literals returned by AddrlistClass method
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000696 getdomainliteral() are now properly wrapped in brackets.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000697
698- site: sys.setdefaultencoding() should only be called in case the
Tim Peters482c0212000-09-26 06:33:09 +0000699 standard default encoding ("ascii") is changed. This saves quite a
Jeremy Hylton1b618592000-09-26 05:32:36 +0000700 few cycles during startup since the first call to
701 setdefaultencoding() will initialize the codec registry and the
702 encodings package.
703
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000704- socket: Support for size hint in readlines() method of object returned
705 by makefile().
Jeremy Hylton1b618592000-09-26 05:32:36 +0000706
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000707- sre: Added experimental expand() method to match objects. Does not
Jeremy Hylton625915e2000-10-02 13:43:33 +0000708 use buffer interface on Unicode strings. Does not hang if group id
Jeremy Hylton1b618592000-09-26 05:32:36 +0000709 is followed by whitespace.
710
Tim Petersa3a3a032000-11-30 05:22:44 +0000711- StringIO: Size hint in readlines() is now supported as documented.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000712
713- struct: Check ranges for bytes and shorts.
714
715- urllib: Improved handling of win32 proxy settings. Fixed quote and
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000716 quote_plus functions so that the always encode a comma.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000717
718- Tkinter: Image objects are now guaranteed to have unique ids. Set
719 event.delta to zero if Tk version doesn't support mousewheel.
720 Removed some debugging prints.
721
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000722- UserList: now implements __contains__().
Jeremy Hylton1b618592000-09-26 05:32:36 +0000723
Fred Drake67233bc2000-09-26 16:40:27 +0000724- webbrowser: On Windows, use os.startfile() instead of os.popen(),
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000725 which works around a bug in Norton AntiVirus 2000 that leads directly
726 to a Blue Screen freeze.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000727
728- xml: New version detection code allows PyXML to override standard
729 XML package if PyXML version is greater than 0.6.1.
730
Fred Drake64bb3802000-09-26 16:21:35 +0000731- xml.dom: DOM level 1 support for basic XML. Includes xml.dom.minidom
732 (conventional DOM), and xml.dom.pulldom, which allows building the DOM
733 tree only for nodes which are sufficiently interesting to a specific
734 application. Does not provide the HTML-specific extensions. Still
735 undocumented.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000736
Fred Drake64bb3802000-09-26 16:21:35 +0000737- xml.sax: SAX 2 support for Python, including all the handler
738 interfaces needed to process XML 1.0 compliant XML. Some
739 documentation is already available.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000740
Fred Drake64bb3802000-09-26 16:21:35 +0000741- pyexpat: Renamed to xml.parsers.expat since this is part of the new,
742 packagized XML support.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000743
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000744
Jeremy Hylton1b618592000-09-26 05:32:36 +0000745C API
746
747- Add three new convenience functions for module initialization --
748 PyModule_AddObject(), PyModule_AddIntConstant(), and
749 PyModule_AddStringConstant().
750
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000751- Cleaned up definition of NULL in C source code; all definitions were
Jeremy Hylton1b618592000-09-26 05:32:36 +0000752 removed and add #error to Python.h if NULL isn't defined after
753 #include of stdio.h.
754
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000755- Py_PROTO() macros that were removed in 2.0b1 have been restored for
Jeremy Hylton1b618592000-09-26 05:32:36 +0000756 backwards compatibility (at the source level) with old extensions.
757
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000758- A wrapper API was added for signal() and sigaction(). Instead of
759 either function, always use PyOS_getsig() to get a signal handler
760 and PyOS_setsig() to set one. A new convenience typedef
761 PyOS_sighandler_t is defined for the type of signal handlers.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000762
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000763- Add PyString_AsStringAndSize() function that provides access to the
Jeremy Hylton1b618592000-09-26 05:32:36 +0000764 internal data buffer and size of a string object -- or the default
765 encoded version of a Unicode object.
766
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000767- PyString_Size() and PyString_AsString() accept Unicode objects.
768
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000769- The standard header <limits.h> is now included by Python.h (if it
Fred Drake64bb3802000-09-26 16:21:35 +0000770 exists). INT_MAX and LONG_MAX will always be defined, even if
771 <limits.h> is not available.
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000772
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000773- PyFloat_FromString takes a second argument, pend, that was
774 effectively useless. It is now officially useless but preserved for
775 backwards compatibility. If the pend argument is not NULL, *pend is
776 set to NULL.
777
778- PyObject_GetAttr() and PyObject_SetAttr() now accept Unicode objects
779 for the attribute name. See note on getattr() above.
780
781- A few bug fixes to argument processing for Unicode.
782 PyArg_ParseTupleAndKeywords() now accepts "es#" and "es".
783 PyArg_Parse() special cases "s#" for Unicode objects; it returns a
784 pointer to the default encoded string data instead of to the raw
Tim Petersa3a3a032000-11-30 05:22:44 +0000785 UTF-16.
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000786
787- Py_BuildValue accepts B format (for bgen-generated code).
788
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000789
Jeremy Hylton1b618592000-09-26 05:32:36 +0000790Internals
791
792- On Unix, fix code for finding Python installation directory so that
793 it works when argv[0] is a relative path.
794
Andrew M. Kuchlinga1099be2000-12-15 01:16:43 +0000795- Added a true unicode_internal_encode() function and fixed the
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000796 unicode_internal_decode function() to support Unicode objects directly
Jeremy Hylton1b618592000-09-26 05:32:36 +0000797 rather than by generating a copy of the object.
798
Tim Peters482c0212000-09-26 06:33:09 +0000799- Several of the internal Unicode tables are much smaller now, and
800 the source code should be much friendlier to weaker compilers.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000801
Jeremy Hylton97693b02000-09-26 17:42:51 +0000802- In the garbage collector: Fixed bug in collection of tuples. Fixed
803 bug that caused some instances to be removed from the container set
804 while they were still live. Fixed parsing in gc.set_debug() for
805 platforms where sizeof(long) > sizeof(int).
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000806
807- Fixed refcount problem in instance deallocation that only occurred
808 when Py_REF_DEBUG was defined and Py_TRACE_REFS was not.
809
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000810- On Windows, getpythonregpath is now protected against null data in
811 registry key.
812
813- On Unix, create .pyc/.pyo files with O_EXCL flag to avoid a race
Tim Petersa3a3a032000-11-30 05:22:44 +0000814 condition.
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000815
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000816
Jeremy Hylton1b618592000-09-26 05:32:36 +0000817Build and platform-specific issues
818
819- Better support of GNU Pth via --with-pth configure option.
820
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000821- Python/C API now properly exposed to dynamically-loaded extension
822 modules on Reliant UNIX.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000823
824- Changes for the benefit of SunOS 4.1.4 (really!). mmapmodule.c:
825 Don't define MS_SYNC to be zero when it is undefined. Added missing
826 prototypes in posixmodule.c.
827
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000828- Improved support for HP-UX build. Threads should now be correctly
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000829 configured (on HP-UX 10.20 and 11.00).
Jeremy Hylton1b618592000-09-26 05:32:36 +0000830
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000831- Fix largefile support on older NetBSD systems and OpenBSD by adding
832 define for TELL64.
833
834
835Tools and other miscellany
836
837- ftpmirror: Call to main() is wrapped in if __name__ == "__main__".
838
839- freeze: The modulefinder now works with 2.0 opcodes.
840
Tim Petersa3a3a032000-11-30 05:22:44 +0000841- IDLE:
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000842 Move hackery of sys.argv until after the Tk instance has been
843 created, which allows the application-specific Tkinter
844 initialization to be executed if present; also pass an explicit
845 className parameter to the Tk() constructor.
Fred Drake64bb3802000-09-26 16:21:35 +0000846
Jeremy Hylton1b618592000-09-26 05:32:36 +0000847
848What's new in 2.0 beta 1?
849=========================
850
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000851Source Incompatibilities
852------------------------
853
854None. Note that 1.6 introduced several incompatibilities with 1.5.2,
855such as single-argument append(), connect() and bind(), and changes to
856str(long) and repr(float).
857
858
859Binary Incompatibilities
860------------------------
861
862- Third party extensions built for Python 1.5.x or 1.6 cannot be used
863with Python 2.0; these extensions will have to be rebuilt for Python
8642.0.
865
866- On Windows, attempting to import a third party extension built for
867Python 1.5.x or 1.6 results in an immediate crash; there's not much we
868can do about this. Check your PYTHONPATH environment variable!
869
870- Python bytecode files (*.pyc and *.pyo) are not compatible between
871releases.
872
873
874Overview of Changes Since 1.6
875-----------------------------
876
877There are many new modules (including brand new XML support through
878the xml package, and i18n support through the gettext module); a list
879of all new modules is included below. Lots of bugs have been fixed.
880
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000881The process for making major new changes to the language has changed
882since Python 1.6. Enhancements must now be documented by a Python
883Enhancement Proposal (PEP) before they can be accepted.
884
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000885There are several important syntax enhancements, described in more
886detail below:
887
888 - Augmented assignment, e.g. x += 1
889
890 - List comprehensions, e.g. [x**2 for x in range(10)]
891
892 - Extended import statement, e.g. import Module as Name
893
894 - Extended print statement, e.g. print >> file, "Hello"
895
896Other important changes:
897
898 - Optional collection of cyclical garbage
899
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000900Python Enhancement Proposal (PEP)
901---------------------------------
902
903PEP stands for Python Enhancement Proposal. A PEP is a design
904document providing information to the Python community, or describing
905a new feature for Python. The PEP should provide a concise technical
906specification of the feature and a rationale for the feature.
907
908We intend PEPs to be the primary mechanisms for proposing new
909features, for collecting community input on an issue, and for
910documenting the design decisions that have gone into Python. The PEP
911author is responsible for building consensus within the community and
912documenting dissenting opinions.
913
914The PEPs are available at http://python.sourceforge.net/peps/.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000915
916Augmented Assignment
917--------------------
918
919This must have been the most-requested feature of the past years!
920Eleven new assignment operators were added:
921
Guido van Rossume905e952000-09-05 12:42:46 +0000922 += -= *= /= %= **= <<= >>= &= ^= |=
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000923
924For example,
925
926 A += B
927
928is similar to
929
930 A = A + B
931
932except that A is evaluated only once (relevant when A is something
933like dict[index].attr).
934
935However, if A is a mutable object, A may be modified in place. Thus,
936if A is a number or a string, A += B has the same effect as A = A+B
937(except A is only evaluated once); but if a is a list, A += B has the
938same effect as A.extend(B)!
939
940Classes and built-in object types can override the new operators in
941order to implement the in-place behavior; the not-in-place behavior is
942used automatically as a fallback when an object doesn't implement the
943in-place behavior. For classes, the method name is derived from the
944method name for the corresponding not-in-place operator by inserting
945an 'i' in front of the name, e.g. __iadd__ implements in-place
946__add__.
947
948Augmented assignment was implemented by Thomas Wouters.
949
950
951List Comprehensions
952-------------------
953
954This is a flexible new notation for lists whose elements are computed
955from another list (or lists). The simplest form is:
956
957 [<expression> for <variable> in <sequence>]
958
Guido van Rossum56db0952000-09-06 23:34:25 +0000959For example, [i**2 for i in range(4)] yields the list [0, 1, 4, 9].
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000960This is more efficient than a for loop with a list.append() call.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000961
962You can also add a condition:
963
964 [<expression> for <variable> in <sequence> if <condition>]
965
966For example, [w for w in words if w == w.lower()] would yield the list
967of words that contain no uppercase characters. This is more efficient
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000968than a for loop with an if statement and a list.append() call.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000969
970You can also have nested for loops and more than one 'if' clause. For
971example, here's a function that flattens a sequence of sequences::
972
973 def flatten(seq):
974 return [x for subseq in seq for x in subseq]
975
976 flatten([[0], [1,2,3], [4,5], [6,7,8,9], []])
977
978This prints
979
980 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
981
982List comprehensions originated as a patch set from Greg Ewing; Skip
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000983Montanaro and Thomas Wouters also contributed. Described by PEP 202.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000984
985
986Extended Import Statement
987-------------------------
988
989Many people have asked for a way to import a module under a different
990name. This can be accomplished like this:
991
992 import foo
993 bar = foo
994 del foo
995
996but this common idiom gets old quickly. A simple extension of the
997import statement now allows this to be written as follows:
998
999 import foo as bar
1000
1001There's also a variant for 'from ... import':
1002
1003 from foo import bar as spam
1004
1005This also works with packages; e.g. you can write this:
1006
1007 import test.regrtest as regrtest
1008
1009Note that 'as' is not a new keyword -- it is recognized only in this
1010context (this is only possible because the syntax for the import
1011statement doesn't involve expressions).
1012
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001013Implemented by Thomas Wouters. Described by PEP 221.
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001014
1015
1016Extended Print Statement
1017------------------------
1018
1019Easily the most controversial new feature, this extension to the print
1020statement adds an option to make the output go to a different file
1021than the default sys.stdout.
1022
1023For example, to write an error message to sys.stderr, you can now
1024write:
1025
1026 print >> sys.stderr, "Error: bad dog!"
1027
1028As a special feature, if the expression used to indicate the file
Fred Drake45888ff2000-09-29 17:09:11 +00001029evaluates to None, the current value of sys.stdout is used. Thus:
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001030
1031 print >> None, "Hello world"
1032
1033is equivalent to
1034
1035 print "Hello world"
1036
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001037Design and implementation by Barry Warsaw. Described by PEP 214.
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001038
1039
1040Optional Collection of Cyclical Garbage
1041---------------------------------------
1042
1043Python is now equipped with a garbage collector that can hunt down
1044cyclical references between Python objects. It's no replacement for
1045reference counting; in fact, it depends on the reference counts being
1046correct, and decides that a set of objects belong to a cycle if all
1047their reference counts can be accounted for from their references to
1048each other. This devious scheme was first proposed by Eric Tiedemann,
1049and brought to implementation by Neil Schemenauer.
1050
1051There's a module "gc" that lets you control some parameters of the
1052garbage collection. There's also an option to the configure script
1053that lets you enable or disable the garbage collection. In 2.0b1,
1054it's on by default, so that we (hopefully) can collect decent user
1055experience with this new feature. There are some questions about its
Fred Drake9f11cf82000-09-29 17:54:40 +00001056performance. If it proves to be too much of a problem, we'll turn it
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001057off by default in the final 2.0 release.
1058
1059
1060Smaller Changes
1061---------------
1062
1063A new function zip() was added. zip(seq1, seq2, ...) is equivalent to
1064map(None, seq1, seq2, ...) when the sequences have the same length;
1065i.e. zip([1,2,3], [10,20,30]) returns [(1,10), (2,20), (3,30)]. When
1066the lists are not all the same length, the shortest list wins:
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001067zip([1,2,3], [10,20]) returns [(1,10), (2,20)]. See PEP 201.
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001068
1069sys.version_info is a tuple (major, minor, micro, level, serial).
1070
1071Dictionaries have an odd new method, setdefault(key, default).
1072dict.setdefault(key, default) returns dict[key] if it exists; if not,
1073it sets dict[key] to default and returns that value. Thus:
1074
1075 dict.setdefault(key, []).append(item)
1076
1077does the same work as this common idiom:
1078
1079 if not dict.has_key(key):
1080 dict[key] = []
1081 dict[key].append(item)
1082
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001083There are two new variants of SyntaxError that are raised for
1084indentation-related errors: IndentationError and TabError.
1085
1086Changed \x to consume exactly two hex digits; see PEP 223. Added \U
1087escape that consumes exactly eight hex digits.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001088
1089The limits on the size of expressions and file in Python source code
1090have been raised from 2**16 to 2**32. Previous versions of Python
1091were limited because the maximum argument size the Python VM accepted
1092was 2**16. This limited the size of object constructor expressions,
1093e.g. [1,2,3] or {'a':1, 'b':2}, and the size of source files. This
1094limit was raised thanks to a patch by Charles Waldman that effectively
1095fixes the problem. It is now much more likely that you will be
1096limited by available memory than by an arbitrary limit in Python.
1097
1098The interpreter's maximum recursion depth can be modified by Python
1099programs using sys.getrecursionlimit and sys.setrecursionlimit. This
1100limit is the maximum number of recursive calls that can be made by
1101Python code. The limit exists to prevent infinite recursion from
1102overflowing the C stack and causing a core dump. The default value is
11031000. The maximum safe value for a particular platform can be found
1104by running Misc/find_recursionlimit.py.
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001105
1106New Modules and Packages
1107------------------------
1108
1109atexit - for registering functions to be called when Python exits.
1110
1111imputil - Greg Stein's alternative API for writing custom import
1112hooks.
1113
1114pyexpat - an interface to the Expat XML parser, contributed by Paul
1115Prescod.
1116
1117xml - a new package with XML support code organized (so far) in three
1118subpackages: xml.dom, xml.sax, and xml.parsers. Describing these
1119would fill a volume. There's a special feature whereby a
1120user-installed package named _xmlplus overrides the standard
1121xmlpackage; this is intended to give the XML SIG a hook to distribute
1122backwards-compatible updates to the standard xml package.
1123
1124webbrowser - a platform-independent API to launch a web browser.
1125
1126
Guido van Rossume905e952000-09-05 12:42:46 +00001127Changed Modules
1128---------------
1129
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001130array -- new methods for array objects: count, extend, index, pop, and
1131remove
1132
1133binascii -- new functions b2a_hex and a2b_hex that convert between
1134binary data and its hex representation
1135
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001136calendar -- Many new functions that support features including control
1137over which day of the week is the first day, returning strings instead
1138of printing them. Also new symbolic constants for days of week,
1139e.g. MONDAY, ..., SUNDAY.
1140
1141cgi -- FieldStorage objects have a getvalue method that works like a
1142dictionary's get method and returns the value attribute of the object.
1143
1144ConfigParser -- The parser object has new methods has_option,
1145remove_section, remove_option, set, and write. They allow the module
1146to be used for writing config files as well as reading them.
1147
1148ftplib -- ntransfercmd(), transfercmd(), and retrbinary() all now
Guido van Rossume905e952000-09-05 12:42:46 +00001149optionally support the RFC 959 REST command.
1150
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001151gzip -- readline and readlines now accept optional size arguments
Guido van Rossume905e952000-09-05 12:42:46 +00001152
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001153httplib -- New interfaces and support for HTTP/1.1 by Greg Stein. See
1154the module doc strings for details.
Guido van Rossum830ca2a2000-09-05 15:34:16 +00001155
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001156locale -- implement getdefaultlocale for Win32 and Macintosh
1157
1158marshal -- no longer dumps core when marshaling deeply nested or
1159recursive data structures
1160
1161os -- new functions isatty, seteuid, setegid, setreuid, setregid
1162
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001163os/popen2 -- popen2/popen3/popen4 support under Windows. popen2/popen3
1164support under Unix.
1165
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001166os/pty -- support for openpty and forkpty
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001167
1168os.path -- fix semantics of os.path.commonprefix
1169
1170smtplib -- support for sending very long messages
1171
1172socket -- new function getfqdn()
1173
1174readline -- new functions to read, write and truncate history files.
1175The readline section of the library reference manual contains an
1176example.
1177
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001178select -- add interface to poll system call
1179
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001180shutil -- new copyfileobj function
1181
1182SimpleHTTPServer, CGIHTTPServer -- Fix problems with buffering in the
1183HTTP server.
1184
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001185Tkinter -- optimization of function flatten
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001186
1187urllib -- scans environment variables for proxy configuration,
Tim Peters8b092332000-09-05 20:15:25 +00001188e.g. http_proxy.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001189
1190whichdb -- recognizes dumbdbm format
Guido van Rossume905e952000-09-05 12:42:46 +00001191
1192
1193Obsolete Modules
1194----------------
1195
1196None. However note that 1.6 made a whole slew of modules obsolete:
1197stdwin, soundex, cml, cmpcache, dircache, dump, find, grep, packmail,
1198poly, zmod, strop, util, whatsound.
1199
1200
1201Changed, New, Obsolete Tools
1202----------------------------
1203
Tim Peters8b092332000-09-05 20:15:25 +00001204None.
Guido van Rossume905e952000-09-05 12:42:46 +00001205
1206
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001207C-level Changes
1208---------------
1209
1210Several cleanup jobs were carried out throughout the source code.
1211
1212All C code was converted to ANSI C; we got rid of all uses of the
1213Py_PROTO() macro, which makes the header files a lot more readable.
1214
1215Most of the portability hacks were moved to a new header file,
1216pyport.h; several other new header files were added and some old
1217header files were removed, in an attempt to create a more rational set
1218of header files. (Few of these ever need to be included explicitly;
1219they are all included by Python.h.)
1220
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001221Trent Mick ensured portability to 64-bit platforms, under both Linux
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001222and Win64, especially for the new Intel Itanium processor. Mick also
1223added large file support for Linux64 and Win64.
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001224
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001225The C APIs to return an object's size have been update to consistently
1226use the form PyXXX_Size, e.g. PySequence_Size and PyDict_Size. In
1227previous versions, the abstract interfaces used PyXXX_Length and the
1228concrete interfaces used PyXXX_Size. The old names,
1229e.g. PyObject_Length, are still available for backwards compatibility
1230at the API level, but are deprecated.
1231
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001232The PyOS_CheckStack function has been implemented on Windows by
1233Fredrik Lundh. It prevents Python from failing with a stack overflow
1234on Windows.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001235
1236The GC changes resulted in creation of two new slots on object,
1237tp_traverse and tp_clear. The augmented assignment changes result in
Guido van Rossum4338a282000-09-06 13:02:08 +00001238the creation of a new slot for each in-place operator.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001239
1240The GC API creates new requirements for container types implemented in
Guido van Rossum4338a282000-09-06 13:02:08 +00001241C extension modules. See Include/objimpl.h for details.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001242
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001243PyErr_Format has been updated to automatically calculate the size of
1244the buffer needed to hold the formatted result string. This change
1245prevents crashes caused by programmer error.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001246
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001247New C API calls: PyObject_AsFileDescriptor, PyErr_WriteUnraisable.
Guido van Rossume905e952000-09-05 12:42:46 +00001248
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001249PyRun_AnyFileEx, PyRun_SimpleFileEx, PyRun_FileEx -- New functions
1250that are the same as their non-Ex counterparts except they take an
1251extra flag argument that tells them to close the file when done.
1252
1253XXX There were other API changes that should be fleshed out here.
Guido van Rossumab9d6f01998-08-10 22:01:13 +00001254
Tim Peters8b092332000-09-05 20:15:25 +00001255
1256Windows Changes
1257---------------
1258
1259New popen2/popen3/peopen4 in os module (see Changed Modules above).
1260
1261os.popen is much more usable on Windows 95 and 98. See Microsoft
1262Knowledge Base article Q150956. The Win9x workaround described there
1263is implemented by the new w9xpopen.exe helper in the root of your
1264Python installation. Note that Python uses this internally; it is not
1265a standalone program.
1266
1267Administrator privileges are no longer required to install Python
1268on Windows NT or Windows 2000. If you have administrator privileges,
1269Python's registry info will be written under HKEY_LOCAL_MACHINE.
1270Otherwise the installer backs off to writing Python's registry info
Guido van Rossum4338a282000-09-06 13:02:08 +00001271under HKEY_CURRENT_USER. The latter is sufficient for all "normal"
Tim Peters8b092332000-09-05 20:15:25 +00001272uses of Python, but will prevent some advanced uses from working
1273(for example, running a Python script as an NT service, or possibly
1274from CGI).
1275
1276[This was new in 1.6] The installer no longer runs a separate Tcl/Tk
1277installer; instead, it installs the needed Tcl/Tk files directly in the
1278Python directory. If you already have a Tcl/Tk installation, this
1279wastes some disk space (about 4 Megs) but avoids problems with
1280conflicting Tcl/Tk installations, and makes it much easier for Python
1281to ensure that Tcl/Tk can find all its files.
1282
1283[This was new in 1.6] The Windows installer now installs by default in
1284\Python20\ on the default volume, instead of \Program Files\Python-2.0\.
1285
Guido van Rossumf62ed9c2000-09-26 11:16:10 +00001286
1287Updates to the changes between 1.5.2 and 1.6
1288--------------------------------------------
1289
1290The 1.6 NEWS file can't be changed after the release is done, so here
1291is some late-breaking news:
1292
1293New APIs in locale.py: normalize(), getdefaultlocale(), resetlocale(),
1294and changes to getlocale() and setlocale().
1295
1296The new module is now enabled per default.
1297
1298It is not true that the encodings codecs cannot be used for normal
1299strings: the string.encode() (which is also present on 8-bit strings
1300!) allows using them for 8-bit strings too, e.g. to convert files from
1301cp1252 (Windows) to latin-1 or vice-versa.
1302
1303Japanese codecs are available from Tamito KAJIYAMA:
1304http://pseudo.grad.sccs.chukyo-u.ac.jp/~kajiyama/python/
1305
1306
Guido van Rossumab9d6f01998-08-10 22:01:13 +00001307======================================================================