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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
Tim Petersee826f82001-01-31 19:39:44 +000094Windows changes
95
96- Build procedure: the zlib project is built in a different way that
97 ensures the zlib header files used can no longer get out of synch with
98 the zlib binary used. See PCbuild\readme.txt for details.
99
Tim Petersd7b5e882001-01-25 03:36:26 +0000100
Tim Petersa3a3a032000-11-30 05:22:44 +0000101What's New in Python 2.1 alpha 1?
102=================================
103
104Core language, builtins, and interpreter
105
Marc-André Lemburgebb195b2001-01-20 10:34:52 +0000106- There is a new Unicode companion to the PyObject_Str() API
107 called PyObject_Unicode(). It behaves in the same way as the
108 former, but assures that the returned value is an Unicode object
109 (applying the usual coercion if necessary).
Marc-André Lemburgad7c98e2001-01-17 17:09:53 +0000110
Guido van Rossumf98eda02001-01-17 15:54:45 +0000111- The comparison operators support "rich comparison overloading" (PEP
112 207). C extension types can provide a rich comparison function in
113 the new tp_richcompare slot in the type object. The cmp() function
114 and the C function PyObject_Compare() first try the new rich
115 comparison operators before trying the old 3-way comparison. There
116 is also a new C API PyObject_RichCompare() (which also falls back on
117 the old 3-way comparison, but does not constrain the outcome of the
118 rich comparison to a Boolean result).
119
120 The rich comparison function takes two objects (at least one of
121 which is guaranteed to have the type that provided the function) and
122 an integer indicating the opcode, which can be Py_LT, Py_LE, Py_EQ,
123 Py_NE, Py_GT, Py_GE (for <, <=, ==, !=, >, >=), and returns a Python
124 object, which may be NotImplemented (in which case the tp_compare
125 slot function is used as a fallback, if defined).
126
127 Classes can overload individual comparison operators by defining one
128 or more of the methods__lt__, __le__, __eq__, __ne__, __gt__,
Guido van Rossuma88479f2001-01-18 14:28:08 +0000129 __ge__. There are no explicit "reflected argument" versions of
130 these; instead, __lt__ and __gt__ are each other's reflection,
131 likewise for__le__ and __ge__; __eq__ and __ne__ are their own
132 reflection (similar at the C level). No other implications are
133 made; in particular, Python does not assume that == is the Boolean
134 inverse of !=, or that < is the Boolean inverse of >=. This makes
135 it possible to define types with partial orderings.
Guido van Rossumf98eda02001-01-17 15:54:45 +0000136
137 Classes or types that want to implement (in)equality tests but not
138 the ordering operators (i.e. unordered types) should implement ==
139 and !=, and raise an error for the ordering operators.
140
Guido van Rossuma88479f2001-01-18 14:28:08 +0000141 It is possible to define types whose rich comparison results are not
Guido van Rossumf98eda02001-01-17 15:54:45 +0000142 Boolean; e.g. a matrix type might want to return a matrix of bits
143 for A < B, giving elementwise comparisons. Such types should ensure
144 that any interpretation of their value in a Boolean context raises
145 an exception, e.g. by defining __nonzero__ (or the tp_nonzero slot
146 at the C level) to always raise an exception.
147
Guido van Rossuma88479f2001-01-18 14:28:08 +0000148- Complex numbers use rich comparisons to define == and != but raise
149 an exception for <, <=, > and >=. Unfortunately, this also means
150 that cmp() of two complex numbers raises an exception when the two
151 numbers differ. Since it is not mathematically meaningful to compare
152 complex numbers except for equality, I hope that this doesn't break
153 too much code.
154
Barry Warsaw573b5412001-01-15 20:43:18 +0000155- Functions and methods now support getting and setting arbitrarily
156 named attributes (PEP 232). Functions have a new __dict__
157 (a.k.a. func_dict) which hold the function attributes. Methods get
158 and set attributes on their underlying im_func. It is a TypeError
159 to set an attribute on a bound method.
160
Guido van Rossum051e3352001-01-15 19:11:10 +0000161- The xrange() object implementation has been improved so that
162 xrange(sys.maxint) can be used on 64-bit platforms. There's still a
163 limitation that in this case len(xrange(sys.maxint)) can't be
164 calculated, but the common idiom "for i in xrange(sys.maxint)" will
165 work fine as long as the index i doesn't actually reach 2**31.
166 (Python uses regular ints for sequence and string indices; fixing
167 that is much more work.)
168
Guido van Rossum1cc8f832001-01-12 16:25:08 +0000169- Two changes to from...import:
170
171 1) "from M import X" now works even if M is not a real module; it's
172 basically a getattr() operation with AttributeError exceptions
173 changed into ImportError.
174
175 2) "from M import *" now looks for M.__all__ to decide which names to
176 import; if M.__all__ doesn't exist, it uses M.__dict__.keys() but
177 filters out names starting with '_' as before. Whether or not
178 __all__ exists, there's no restriction on the type of M.
179
Guido van Rossumf61f1662001-01-10 20:13:55 +0000180- File objects have a new method, xreadlines(). This is the fastest
181 way to iterate over all lines in a file:
182
183 for line in file.xreadlines():
184 ...do something to line...
185
186 See the xreadlines module (mentioned below) for how to do this for
187 other file-like objects.
188
189- Even if you don't use file.xreadlines(), you may expect a speedup on
190 line-by-line input. The file.readline() method has been optimized
Tim Petersf29b64d2001-01-15 06:33:19 +0000191 quite a bit in platform-specific ways: on systems (like Linux) that
192 support flockfile(), getc_unlocked(), and funlockfile(), those are
193 used by default. On systems (like Windows) without getc_unlocked(),
194 a complicated (but still thread-safe) method using fgets() is used by
195 default.
196
Tim Petersd52269b2001-01-25 06:23:18 +0000197 You can force use of the fgets() method by #define'ing
198 USE_FGETS_IN_GETLINE at build time (it may be faster than
Tim Petersf29b64d2001-01-15 06:33:19 +0000199 getc_unlocked()).
200
Tim Petersd52269b2001-01-25 06:23:18 +0000201 You can force fgets() not to be used by #define'ing
202 DONT_USE_FGETS_IN_GETLINE (this is the first thing to try if std test
Tim Petersf29b64d2001-01-15 06:33:19 +0000203 test_bufio.py fails -- and let us know if it does!).
204
205- In addition, the fileinput module, while still slower than the other
206 methods on most platforms, has been sped up too, by using
207 file.readlines(sizehint).
Guido van Rossumf61f1662001-01-10 20:13:55 +0000208
209- Support for run-time warnings has been added, including a new
210 command line option (-W) to specify the disposition of warnings.
211 See the description of the warnings module below.
212
213- Extensive changes have been made to the coercion code. This mostly
214 affects extension modules (which can now implement mixed-type
215 numerical operators without having to use coercion), but
216 occasionally, in boundary cases the coercion semantics have changed
217 subtly. Since this was a terrible gray area of the language, this
Guido van Rossumae72d872001-01-11 15:00:14 +0000218 is considered an improvement. Also note that __rcmp__ is no longer
Guido van Rossumf61f1662001-01-10 20:13:55 +0000219 supported -- instead of calling __rcmp__, __cmp__ is called with
Guido van Rossuma88479f2001-01-18 14:28:08 +0000220 reflected arguments.
Guido van Rossumf61f1662001-01-10 20:13:55 +0000221
Guido van Rossumf98eda02001-01-17 15:54:45 +0000222- In connection with the coercion changes, a new built-in singleton
223 object, NotImplemented is defined. This can be returned for
224 operations that wish to indicate they are not implemented for a
225 particular combination of arguments. From C, this is
226 Py_NotImplemented.
227
Martin v. Löwisbe4c0f52001-01-04 20:30:56 +0000228- The interpreter accepts now bytecode files on the command line even
229 if they do not have a .pyc or .pyo extension. On Linux, after executing
230
231 echo ':pyc:M::\x87\xc6\x0d\x0a::/usr/local/bin/python:' > /proc/sys/fs/binfmt_misc/register
232
233 any byte code file can be used as an executable (i.e. as an argument
234 to execve(2)).
235
Tim Peters9940b802000-12-01 07:59:35 +0000236- %[xXo] formats of negative Python longs now produce a sign
Tim Petersa3a3a032000-11-30 05:22:44 +0000237 character. In 1.6 and earlier, they never produced a sign,
238 and raised an error if the value of the long was too large
239 to fit in a Python int. In 2.0, they produced a sign if and
240 only if too large to fit in an int. This was inconsistent
241 across platforms (because the size of an int varies across
242 platforms), and inconsistent with hex() and oct(). Example:
243
244 >>> "%x" % -0x42L
Tim Peters9940b802000-12-01 07:59:35 +0000245 '-42' # in 2.1
Tim Petersa3a3a032000-11-30 05:22:44 +0000246 'ffffffbe' # in 2.0 and before, on 32-bit machines
247 >>> hex(-0x42L)
248 '-0x42L' # in all versions of Python
249
Tim Peters9940b802000-12-01 07:59:35 +0000250 The behavior of %d formats for negative Python longs remains
251 the same as in 2.0 (although in 1.6 and before, they raised
252 an error if the long didn't fit in a Python int).
253
254 %u formats don't make sense for Python longs, but are allowed
255 and treated the same as %d in 2.1. In 2.0, a negative long
256 formatted via %u produced a sign if and only if too large to
257 fit in an int. In 1.6 and earlier, a negative long formatted
258 via %u raised an error if it was too big to fit in an int.
259
Guido van Rossum3661d392000-12-12 22:10:31 +0000260- Dictionary objects have an odd new method, popitem(). This removes
261 an arbitrary item from the dictionary and returns it (in the form of
262 a (key, value) pair). This can be useful for algorithms that use a
263 dictionary as a bag of "to do" items and repeatedly need to pick one
264 item. Such algorithms normally end up running in quadratic time;
265 using popitem() they can usually be made to run in linear time.
266
Tim Peters36cdad12000-12-29 02:06:45 +0000267Standard library
268
Thomas Woutersfe385252001-01-19 23:16:56 +0000269- In the time module, the time argument to the functions strftime,
270 localtime, gmtime, asctime and ctime is now optional, defaulting to
271 the current time (in the local timezone).
272
Guido van Rossumda91f222001-01-15 16:36:08 +0000273- The ftplib module now defaults to passive mode, which is deemed a
274 more useful default given that clients are often inside firewalls
275 these days. Note that this could break if ftplib is used to connect
276 to a *server* that is inside a firewall, from outside; this is
277 expected to be a very rare situation. To fix that, you can call
278 ftp.set_pasv(0).
279
Martin v. Löwis10a27872001-01-13 09:54:41 +0000280- The module site now treats .pth files not only for path configuration,
281 but also supports extensions to the initialization code: Lines starting
282 with import are executed.
283
Guido van Rossumf61f1662001-01-10 20:13:55 +0000284- There's a new module, warnings, which implements a mechanism for
285 issuing and filtering warnings. There are some new built-in
286 exceptions that serve as warning categories, and a new command line
287 option, -W, to control warnings (e.g. -Wi ignores all warnings, -We
288 turns warnings into errors). warnings.warn(message[, category])
289 issues a warning message; this can also be called from C as
290 PyErr_Warn(category, message).
291
292- A new module xreadlines was added. This exports a single factory
293 function, xreadlines(). The intention is that this code is the
294 absolutely fastest way to iterate over all lines in an open
295 file(-like) object:
296
297 import xreadlines
298 for line in xreadlines.xreadlines(file):
299 ...do something to line...
300
301 This is equivalent to the previous the speed record holder using
302 file.readlines(sizehint). Note that if file is a real file object
303 (as opposed to a file-like object), this is equivalent:
304
305 for line in file.xreadlines():
306 ...do something to line...
307
Tim Peters36cdad12000-12-29 02:06:45 +0000308- The bisect module has new functions bisect_left, insort_left,
309 bisect_right and insort_right. The old names bisect and insort
310 are now aliases for bisect_right and insort_right. XXX_right
311 and XXX_left methods differ in what happens when the new element
312 compares equal to one or more elements already in the list: the
313 XXX_left methods insert to the left, the XXX_right methods to the
Tim Peters742bb6f2001-01-05 08:05:32 +0000314 right. Code that doesn't care where equal elements end up should
315 continue to use the old, short names ("bisect" and "insort").
Tim Peters36cdad12000-12-29 02:06:45 +0000316
Andrew M. Kuchlingf6f3a892001-01-13 14:53:34 +0000317- The new curses.panel module wraps the panel library that forms part
318 of SYSV curses and ncurses. Contributed by Thomas Gellekum.
319
Guido van Rossumf61f1662001-01-10 20:13:55 +0000320- The SocketServer module now sets the allow_reuse_address flag by
321 default in the TCPServer class.
322
323- A new function, sys._getframe(), returns the stack frame pointer of
324 the caller. This is intended only as a building block for
325 higher-level mechanisms such as string interpolation.
326
327Build issues
328
Guido van Rossum1e33bdc2001-01-23 03:17:00 +0000329- For Unix (and Unix-compatible) builds, configuration and building of
330 extension modules is now greatly automated. Rather than having to
331 edit the Modules/Setup file to indicate which modules should be
332 built and where their include files and libraries are, a
333 distutils-based setup.py script now takes care of building most
334 extension modules. All extension modules built this way are built
335 as shared libraries. Only a few modules that must be linked
336 statically are still listed in the Setup file; you won't need to
337 edit their configuration.
338
339- Python should now build out of the box on Cygwin. If it doesn't,
340 mail to Jason Tishler (jlt63 at users.sourceforge.net).
Guido van Rossumf61f1662001-01-10 20:13:55 +0000341
342- Python now always uses its own (renamed) implementation of getopt()
343 -- there's too much variation among C library getopt()
344 implementations.
345
346- C++ compilers are better supported; the CXX macro is always set to a
347 C++ compiler if one is found.
Tim Peters36cdad12000-12-29 02:06:45 +0000348
Tim Petersd92dfe02000-12-12 01:18:41 +0000349Windows changes
350
351- select module: By default under Windows, a select() call
352 can specify no more than 64 sockets. Python now boosts
353 this Microsoft default to 512. If you need even more than
354 that, see the MS docs (you'll need to #define FD_SETSIZE
355 and recompile Python from source).
356
Guido van Rossumf61f1662001-01-10 20:13:55 +0000357- Support for Windows 3.1, DOS and OS/2 is gone. The Lib/dos-8x3
358 subdirectory is no more!
359
Tim Petersa3a3a032000-11-30 05:22:44 +0000360
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000361What's New in Python 2.0?
Fred Drake1a640502000-10-16 20:27:25 +0000362=========================
Guido van Rossum61000331997-08-15 04:39:58 +0000363
Guido van Rossum8ed602b2000-09-01 22:34:33 +0000364Below is a list of all relevant changes since release 1.6. Older
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000365changes are in the file HISTORY. If you are making the jump directly
366from Python 1.5.2 to 2.0, make sure to read the section for 1.6 in the
367HISTORY file! Many important changes listed there.
Guido van Rossum61000331997-08-15 04:39:58 +0000368
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000369Alternatively, a good overview of the changes between 1.5.2 and 2.0 is
370the document "What's New in Python 2.0" by Kuchling and Moshe Zadka:
371http://starship.python.net/crew/amk/python/writing/new-python/.
Guido van Rossum1f83cce1997-10-06 21:04:35 +0000372
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000373--Guido van Rossum (home page: http://www.pythonlabs.com/~guido/)
Guido van Rossum437cfe81999-04-08 20:17:57 +0000374
375======================================================================
376
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000377What's new in 2.0 (since release candidate 1)?
378==============================================
379
380Standard library
381
382- The copy_reg module was modified to clarify its intended use: to
383 register pickle support for extension types, not for classes.
384 pickle() will raise a TypeError if it is passed a class.
385
386- Fixed a bug in gettext's "normalize and expand" code that prevented
387 it from finding an existing .mo file.
388
389- Restored support for HTTP/0.9 servers in httplib.
390
Tim Peters989b7b92000-10-16 20:24:53 +0000391- The math module was changed to stop raising OverflowError in case of
392 underflow, and return 0 instead in underflow cases. Whether Python
393 used to raise OverflowError in case of underflow was platform-
394 dependent (it did when the platform math library set errno to ERANGE
395 on underflow).
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000396
397- Fixed a bug in StringIO that occurred when the file position was not
398 at the end of the file and write() was called with enough data to
399 extend past the end of the file.
400
401- Fixed a bug that caused Tkinter error messages to get lost on
402 Windows. The bug was fixed by replacing direct use of
403 interp->result with Tcl_GetStringResult(interp).
404
405- Fixed bug in urllib2 that caused it to fail when it received an HTTP
406 redirect response.
407
408- Several changes were made to distutils: Some debugging code was
409 removed from util. Fixed the installer used when an external zip
410 program (like WinZip) is not found; the source code for this
411 installer is in Misc/distutils. check_lib() was modified to behave
412 more like AC_CHECK_LIB by add other_libraries() as a parameter. The
413 test for whether installed modules are on sys.path was changed to
414 use both normcase() and normpath().
415
Jeremy Hyltond867a2c2000-10-16 20:41:38 +0000416- Several minor bugs were fixed in the xml package (the minidom,
417 pulldom, expatreader, and saxutils modules).
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000418
419- The regression test driver (regrtest.py) behavior when invoked with
420 -l changed: It now reports a count of objects that are recognized as
421 garbage but not freed by the garbage collector.
422
Tim Peters989b7b92000-10-16 20:24:53 +0000423- The regression test for the math module was changed to test
424 exceptional behavior when the test is run in verbose mode. Python
425 cannot yet guarantee consistent exception behavior across platforms,
426 so the exception part of test_math is run only in verbose mode, and
427 may fail on your platform.
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000428
429Internals
430
431- PyOS_CheckStack() has been disabled on Win64, where it caused
432 test_sre to fail.
433
434Build issues
435
436- Changed compiler flags, so that gcc is always invoked with -Wall and
437 -Wstrict-prototypes. Users compiling Python with GCC should see
438 exactly one warning, except if they have passed configure the
Tim Peters989b7b92000-10-16 20:24:53 +0000439 --with-pydebug flag. The expected warning is for getopt() in
Tim Petersadfb94f2000-10-16 20:51:33 +0000440 Modules/main.c. This warning will be fixed for Python 2.1.
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000441
Tim Petersa3a3a032000-11-30 05:22:44 +0000442- Fixed configure to add -threads argument during linking on OSF1.
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000443
444Tools and other miscellany
445
446- The compiler in Tools/compiler was updated to support the new
447 language features introduced in 2.0: extended print statement, list
448 comprehensions, and augmented assignments. The new compiler should
449 also be backwards compatible with Python 1.5.2; the compiler will
450 always generate code for the version of the interpreter it runs
Tim Petersa3a3a032000-11-30 05:22:44 +0000451 under.
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000452
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000453What's new in 2.0 release candidate 1 (since beta 2)?
454=====================================================
455
Jeremy Hylton6040aaa2000-10-09 21:27:22 +0000456What is release candidate 1?
457
458We believe that release candidate 1 will fix all known bugs that we
459intend to fix for the 2.0 final release. This release should be a bit
460more stable than the previous betas. We would like to see even more
461widespread testing before the final release, so we are producing this
462release candidate. The final release will be exactly the same unless
463any show-stopping (or brown bag) bugs are found by testers of the
464release candidate.
465
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000466All the changes since the last beta release are bug fixes or changes
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000467to support building Python for specific platforms.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000468
469Core language, builtins, and interpreter
470
471- A bug that caused crashes when __coerce__ was used with augmented
472 assignment, e.g. +=, was fixed.
473
474- Raise ZeroDivisionError when raising zero to a negative number,
475 e.g. 0.0 ** -2.0. Note that math.pow is unrelated to the builtin
476 power operator and the result of math.pow(0.0, -2.0) will vary by
477 platform. On Linux, it raises a ValueError.
478
479- A bug in Unicode string interpolation was fixed that occasionally
480 caused errors with formats including "%%". For example, the
481 following expression "%% %s" % u"abc" no longer raises a TypeError.
482
483- Compilation of deeply nested expressions raises MemoryError instead
484 of SyntaxError, e.g. eval("[" * 50 + "]" * 50).
485
486- In 2.0b2 on Windows, the interpreter wrote .pyc files in text mode,
487 rendering them useless. They are now written in binary mode again.
488
489Standard library
490
491- Keyword arguments are now accepted for most pattern and match object
492 methods in SRE, the standard regular expression engine.
493
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000494- In SRE, fixed error with negative lookahead and lookbehind that
Jeremy Hylton32e20ff2000-10-09 19:48:11 +0000495 manifested itself as a runtime error in patterns like "(?<!abc)(def)".
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000496
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000497- Several bugs in the Unicode handling and error handling in _tkinter
498 were fixed.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000499
500- Fix memory management errors in Merge() and Tkapp_Call() routines.
501
502- Several changes were made to cStringIO to make it compatible with
503 the file-like object interface and with StringIO. If operations are
504 performed on a closed object, an exception is raised. The truncate
505 method now accepts a position argument and readline accepts a size
Tim Petersa3a3a032000-11-30 05:22:44 +0000506 argument.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000507
508- There were many changes made to the linuxaudiodev module and its
509 test suite; as a result, a short, unexpected audio sample should now
Tim Petersa3a3a032000-11-30 05:22:44 +0000510 play when the regression test is run.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000511
512 Note that this module is named poorly, because it should work
513 correctly on any platform that supports the Open Sound System
Tim Petersa3a3a032000-11-30 05:22:44 +0000514 (OSS).
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000515
516 The module now raises exceptions when errors occur instead of
517 crashing. It also defines the AFMT_A_LAW format (logarithmic A-law
518 audio) and defines a getptr() method that calls the
519 SNDCTL_DSP_GETxPTR ioctl defined in the OSS Programmer's Guide.
520
521- The library_version attribute, introduced in an earlier beta, was
522 removed because it can not be supported with early versions of the C
523 readline library, which provides no way to determine the version at
524 compile-time.
525
526- The binascii module is now enabled on Win64.
527
Tim Peters46446d62000-10-09 21:19:31 +0000528- tokenize.py no longer suffers "recursion depth" errors when parsing
529 programs with very long string literals.
530
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000531Internals
532
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000533- Fixed several buffer overflow vulnerabilities in calculate_path(),
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000534 which is called when the interpreter starts up to determine where
535 the standard library is installed. These vulnerabilities affect all
536 previous versions of Python and can be exploited by setting very
537 long values for PYTHONHOME or argv[0]. The risk is greatest for a
538 setuid Python script, although use of the wrapper in
539 Misc/setuid-prog.c will eliminate the vulnerability.
540
541- Fixed garbage collection bugs in instance creation that were
542 triggered when errors occurred during initialization. The solution,
543 applied in cPickle and in PyInstance_New(), is to call
544 PyObject_GC_Init() after the initialization of the object's
545 container attributes is complete.
546
547- pyexpat adds definitions of PyModule_AddStringConstant and
548 PyModule_AddObject if the Python version is less than 2.0, which
549 provides compatibility with PyXML on Python 1.5.2.
550
551- If the platform has a bogus definition for LONG_BIT (the number of
552 bits in a long), an error will be reported at compile time.
553
554- Fix bugs in _PyTuple_Resize() which caused hard-to-interpret garbage
555 collection crashes and possibly other, unreported crashes.
556
557- Fixed a memory leak in _PyUnicode_Fini().
558
559Build issues
560
561- configure now accepts a --with-suffix option that specifies the
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000562 executable suffix. This is useful for builds on Cygwin and Mac OS
Tim Petersa3a3a032000-11-30 05:22:44 +0000563 X, for example.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000564
565- The mmap.PAGESIZE constant is now initialized using sysconf when
566 possible, which eliminates a dependency on -lucb for Reliant UNIX.
567
568- The md5 file should now compile on all platforms.
569
570- The select module now compiles on platforms that do not define
571 POLLRDNORM and related constants.
572
573- Darwin (Mac OS X): Initial support for static builds on this
Tim Petersa3a3a032000-11-30 05:22:44 +0000574 platform.
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000575
Jeremy Hylton10921202000-10-09 18:34:12 +0000576- BeOS: A number of changes were made to the build and installation
577 process. ar-fake now operates on a directory of object files.
578 dl_export.h is gone, and its macros now appear on the mwcc command
579 line during build on PPC BeOS.
580
Jeremy Hyltond6e20232000-10-16 20:08:38 +0000581- Platform directory in lib/python2.0 is "plat-beos5" (or
Jeremy Hylton10921202000-10-09 18:34:12 +0000582 "plat-beos4", if building on BeOS 4.5), rather than "plat-beos".
Jeremy Hyltoned9e6442000-10-09 18:26:42 +0000583
584- Cygwin: Support for shared libraries, Tkinter, and sockets.
585
586- SunOS 4.1.4_JL: Fix test for directory existence in configure.
587
588Tools and other miscellany
589
590- Removed debugging prints from main used with freeze.
591
Tim Peters46446d62000-10-09 21:19:31 +0000592- IDLE auto-indent no longer crashes when it encounters Unicode
593 characters.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000594
595What's new in 2.0 beta 2 (since beta 1)?
596========================================
597
598Core language, builtins, and interpreter
599
Tim Peters482c0212000-09-26 06:33:09 +0000600- Add support for unbounded ints in %d,i,u,x,X,o formats; for example
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000601 "%d" % 2L**64 == "18446744073709551616".
Jeremy Hylton1b618592000-09-26 05:32:36 +0000602
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000603- Add -h and -V command line options to print the usage message and
604 Python version number and exit immediately.
605
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000606- eval() and exec accept Unicode objects as code parameters.
607
608- getattr() and setattr() now also accept Unicode objects for the
609 attribute name, which are converted to strings using the default
610 encoding before lookup.
611
612- Multiplication on string and Unicode now does proper bounds
613 checking; e.g. 'a' * 65536 * 65536 will raise ValueError, "repeated
614 string is too long."
615
616- Better error message when continue is found in try statement in a
Tim Petersa3a3a032000-11-30 05:22:44 +0000617 loop.
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000618
Jeremy Hylton1b618592000-09-26 05:32:36 +0000619
620Standard library and extensions
621
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000622- array: reverse() method of array now works. buffer_info() now does
Jeremy Hylton1b618592000-09-26 05:32:36 +0000623 argument checking; it still takes no arguments.
624
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000625- asyncore/asynchat: Included most recent version from Sam Rushing.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000626
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000627- cgi: Accept '&' or ';' as separator characters when parsing form data.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000628
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000629- CGIHTTPServer: Now works on Windows (and perhaps even Mac).
Jeremy Hylton1b618592000-09-26 05:32:36 +0000630
631- ConfigParser: When reading the file, options spelled in upper case
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000632 letters are now correctly converted to lowercase.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000633
634- copy: Copy Unicode objects atomically.
635
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000636- cPickle: Fail gracefully when copy_reg can't be imported.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000637
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000638- cStringIO: Implemented readlines() method.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000639
Fred Drake67233bc2000-09-26 16:40:27 +0000640- dbm: Add get() and setdefault() methods to dbm object. Add constant
641 `library' to module that names the library used. Added doc strings
642 and method names to error messages. Uses configure to determine
643 which ndbm.h file to include; Berkeley DB's nbdm and GDBM's ndbm is
644 now available options.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000645
646- distutils: Update to version 0.9.3.
647
648- dl: Add several dl.RTLD_ constants.
649
650- fpectl: Now supported on FreeBSD.
651
652- gc: Add DEBUG_SAVEALL option. When enabled all garbage objects
653 found by the collector will be saved in gc.garbage. This is useful
654 for debugging a program that creates reference cycles.
655
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000656- httplib: Three changes: Restore support for set_debuglevel feature
Jeremy Hylton1b618592000-09-26 05:32:36 +0000657 of HTTP class. Do not close socket on zero-length response. Do not
658 crash when server sends invalid content-length header.
659
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000660- mailbox: Mailbox class conforms better to qmail specifications.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000661
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000662- marshal: When reading a short, sign-extend on platforms where shorts
663 are bigger than 16 bits. When reading a long, repair the unportable
664 sign extension that was being done for 64-bit machines. (It assumed
665 that signed right shift sign-extends.)
666
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000667- operator: Add contains(), invert(), __invert__() as aliases for
668 __contains__(), inv(), and __inv__() respectively.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000669
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000670- os: Add support for popen2() and popen3() on all platforms where
671 fork() exists. (popen4() is still in the works.)
Jeremy Hylton1b618592000-09-26 05:32:36 +0000672
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000673- os: (Windows only:) Add startfile() function that acts like double-
Tim Peters482c0212000-09-26 06:33:09 +0000674 clicking on a file in Explorer (or passing the file name to the
675 DOS "start" command).
Jeremy Hylton1b618592000-09-26 05:32:36 +0000676
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000677- os.path: (Windows, DOS:) Treat trailing colon correctly in
Tim Peters482c0212000-09-26 06:33:09 +0000678 os.path.join. os.path.join("a:", "b") yields "a:b".
Jeremy Hylton1b618592000-09-26 05:32:36 +0000679
680- pickle: Now raises ValueError when an invalid pickle that contains
681 a non-string repr where a string repr was expected. This behavior
682 matches cPickle.
683
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000684- posixfile: Remove broken __del__() method.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000685
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000686- py_compile: support CR+LF line terminators in source file.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000687
688- readline: Does not immediately exit when ^C is hit when readline and
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000689 threads are configured. Adds definition of rl_library_version. (The
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000690 latter addition requires GNU readline 2.2 or later.)
Jeremy Hylton1b618592000-09-26 05:32:36 +0000691
692- rfc822: Domain literals returned by AddrlistClass method
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000693 getdomainliteral() are now properly wrapped in brackets.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000694
695- site: sys.setdefaultencoding() should only be called in case the
Tim Peters482c0212000-09-26 06:33:09 +0000696 standard default encoding ("ascii") is changed. This saves quite a
Jeremy Hylton1b618592000-09-26 05:32:36 +0000697 few cycles during startup since the first call to
698 setdefaultencoding() will initialize the codec registry and the
699 encodings package.
700
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000701- socket: Support for size hint in readlines() method of object returned
702 by makefile().
Jeremy Hylton1b618592000-09-26 05:32:36 +0000703
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000704- sre: Added experimental expand() method to match objects. Does not
Jeremy Hylton625915e2000-10-02 13:43:33 +0000705 use buffer interface on Unicode strings. Does not hang if group id
Jeremy Hylton1b618592000-09-26 05:32:36 +0000706 is followed by whitespace.
707
Tim Petersa3a3a032000-11-30 05:22:44 +0000708- StringIO: Size hint in readlines() is now supported as documented.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000709
710- struct: Check ranges for bytes and shorts.
711
712- urllib: Improved handling of win32 proxy settings. Fixed quote and
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000713 quote_plus functions so that the always encode a comma.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000714
715- Tkinter: Image objects are now guaranteed to have unique ids. Set
716 event.delta to zero if Tk version doesn't support mousewheel.
717 Removed some debugging prints.
718
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000719- UserList: now implements __contains__().
Jeremy Hylton1b618592000-09-26 05:32:36 +0000720
Fred Drake67233bc2000-09-26 16:40:27 +0000721- webbrowser: On Windows, use os.startfile() instead of os.popen(),
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000722 which works around a bug in Norton AntiVirus 2000 that leads directly
723 to a Blue Screen freeze.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000724
725- xml: New version detection code allows PyXML to override standard
726 XML package if PyXML version is greater than 0.6.1.
727
Fred Drake64bb3802000-09-26 16:21:35 +0000728- xml.dom: DOM level 1 support for basic XML. Includes xml.dom.minidom
729 (conventional DOM), and xml.dom.pulldom, which allows building the DOM
730 tree only for nodes which are sufficiently interesting to a specific
731 application. Does not provide the HTML-specific extensions. Still
732 undocumented.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000733
Fred Drake64bb3802000-09-26 16:21:35 +0000734- xml.sax: SAX 2 support for Python, including all the handler
735 interfaces needed to process XML 1.0 compliant XML. Some
736 documentation is already available.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000737
Fred Drake64bb3802000-09-26 16:21:35 +0000738- pyexpat: Renamed to xml.parsers.expat since this is part of the new,
739 packagized XML support.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000740
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000741
Jeremy Hylton1b618592000-09-26 05:32:36 +0000742C API
743
744- Add three new convenience functions for module initialization --
745 PyModule_AddObject(), PyModule_AddIntConstant(), and
746 PyModule_AddStringConstant().
747
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000748- Cleaned up definition of NULL in C source code; all definitions were
Jeremy Hylton1b618592000-09-26 05:32:36 +0000749 removed and add #error to Python.h if NULL isn't defined after
750 #include of stdio.h.
751
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000752- Py_PROTO() macros that were removed in 2.0b1 have been restored for
Jeremy Hylton1b618592000-09-26 05:32:36 +0000753 backwards compatibility (at the source level) with old extensions.
754
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000755- A wrapper API was added for signal() and sigaction(). Instead of
756 either function, always use PyOS_getsig() to get a signal handler
757 and PyOS_setsig() to set one. A new convenience typedef
758 PyOS_sighandler_t is defined for the type of signal handlers.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000759
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000760- Add PyString_AsStringAndSize() function that provides access to the
Jeremy Hylton1b618592000-09-26 05:32:36 +0000761 internal data buffer and size of a string object -- or the default
762 encoded version of a Unicode object.
763
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000764- PyString_Size() and PyString_AsString() accept Unicode objects.
765
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000766- The standard header <limits.h> is now included by Python.h (if it
Fred Drake64bb3802000-09-26 16:21:35 +0000767 exists). INT_MAX and LONG_MAX will always be defined, even if
768 <limits.h> is not available.
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000769
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000770- PyFloat_FromString takes a second argument, pend, that was
771 effectively useless. It is now officially useless but preserved for
772 backwards compatibility. If the pend argument is not NULL, *pend is
773 set to NULL.
774
775- PyObject_GetAttr() and PyObject_SetAttr() now accept Unicode objects
776 for the attribute name. See note on getattr() above.
777
778- A few bug fixes to argument processing for Unicode.
779 PyArg_ParseTupleAndKeywords() now accepts "es#" and "es".
780 PyArg_Parse() special cases "s#" for Unicode objects; it returns a
781 pointer to the default encoded string data instead of to the raw
Tim Petersa3a3a032000-11-30 05:22:44 +0000782 UTF-16.
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000783
784- Py_BuildValue accepts B format (for bgen-generated code).
785
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000786
Jeremy Hylton1b618592000-09-26 05:32:36 +0000787Internals
788
789- On Unix, fix code for finding Python installation directory so that
790 it works when argv[0] is a relative path.
791
Andrew M. Kuchlinga1099be2000-12-15 01:16:43 +0000792- Added a true unicode_internal_encode() function and fixed the
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000793 unicode_internal_decode function() to support Unicode objects directly
Jeremy Hylton1b618592000-09-26 05:32:36 +0000794 rather than by generating a copy of the object.
795
Tim Peters482c0212000-09-26 06:33:09 +0000796- Several of the internal Unicode tables are much smaller now, and
797 the source code should be much friendlier to weaker compilers.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000798
Jeremy Hylton97693b02000-09-26 17:42:51 +0000799- In the garbage collector: Fixed bug in collection of tuples. Fixed
800 bug that caused some instances to be removed from the container set
801 while they were still live. Fixed parsing in gc.set_debug() for
802 platforms where sizeof(long) > sizeof(int).
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000803
804- Fixed refcount problem in instance deallocation that only occurred
805 when Py_REF_DEBUG was defined and Py_TRACE_REFS was not.
806
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000807- On Windows, getpythonregpath is now protected against null data in
808 registry key.
809
810- On Unix, create .pyc/.pyo files with O_EXCL flag to avoid a race
Tim Petersa3a3a032000-11-30 05:22:44 +0000811 condition.
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000812
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000813
Jeremy Hylton1b618592000-09-26 05:32:36 +0000814Build and platform-specific issues
815
816- Better support of GNU Pth via --with-pth configure option.
817
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000818- Python/C API now properly exposed to dynamically-loaded extension
819 modules on Reliant UNIX.
Jeremy Hylton1b618592000-09-26 05:32:36 +0000820
821- Changes for the benefit of SunOS 4.1.4 (really!). mmapmodule.c:
822 Don't define MS_SYNC to be zero when it is undefined. Added missing
823 prototypes in posixmodule.c.
824
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000825- Improved support for HP-UX build. Threads should now be correctly
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000826 configured (on HP-UX 10.20 and 11.00).
Jeremy Hylton1b618592000-09-26 05:32:36 +0000827
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000828- Fix largefile support on older NetBSD systems and OpenBSD by adding
829 define for TELL64.
830
831
832Tools and other miscellany
833
834- ftpmirror: Call to main() is wrapped in if __name__ == "__main__".
835
836- freeze: The modulefinder now works with 2.0 opcodes.
837
Tim Petersa3a3a032000-11-30 05:22:44 +0000838- IDLE:
Jeremy Hyltonfa2e2c12000-09-26 16:31:30 +0000839 Move hackery of sys.argv until after the Tk instance has been
840 created, which allows the application-specific Tkinter
841 initialization to be executed if present; also pass an explicit
842 className parameter to the Tk() constructor.
Fred Drake64bb3802000-09-26 16:21:35 +0000843
Jeremy Hylton1b618592000-09-26 05:32:36 +0000844
845What's new in 2.0 beta 1?
846=========================
847
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000848Source Incompatibilities
849------------------------
850
851None. Note that 1.6 introduced several incompatibilities with 1.5.2,
852such as single-argument append(), connect() and bind(), and changes to
853str(long) and repr(float).
854
855
856Binary Incompatibilities
857------------------------
858
859- Third party extensions built for Python 1.5.x or 1.6 cannot be used
860with Python 2.0; these extensions will have to be rebuilt for Python
8612.0.
862
863- On Windows, attempting to import a third party extension built for
864Python 1.5.x or 1.6 results in an immediate crash; there's not much we
865can do about this. Check your PYTHONPATH environment variable!
866
867- Python bytecode files (*.pyc and *.pyo) are not compatible between
868releases.
869
870
871Overview of Changes Since 1.6
872-----------------------------
873
874There are many new modules (including brand new XML support through
875the xml package, and i18n support through the gettext module); a list
876of all new modules is included below. Lots of bugs have been fixed.
877
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000878The process for making major new changes to the language has changed
879since Python 1.6. Enhancements must now be documented by a Python
880Enhancement Proposal (PEP) before they can be accepted.
881
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000882There are several important syntax enhancements, described in more
883detail below:
884
885 - Augmented assignment, e.g. x += 1
886
887 - List comprehensions, e.g. [x**2 for x in range(10)]
888
889 - Extended import statement, e.g. import Module as Name
890
891 - Extended print statement, e.g. print >> file, "Hello"
892
893Other important changes:
894
895 - Optional collection of cyclical garbage
896
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000897Python Enhancement Proposal (PEP)
898---------------------------------
899
900PEP stands for Python Enhancement Proposal. A PEP is a design
901document providing information to the Python community, or describing
902a new feature for Python. The PEP should provide a concise technical
903specification of the feature and a rationale for the feature.
904
905We intend PEPs to be the primary mechanisms for proposing new
906features, for collecting community input on an issue, and for
907documenting the design decisions that have gone into Python. The PEP
908author is responsible for building consensus within the community and
909documenting dissenting opinions.
910
911The PEPs are available at http://python.sourceforge.net/peps/.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000912
913Augmented Assignment
914--------------------
915
916This must have been the most-requested feature of the past years!
917Eleven new assignment operators were added:
918
Guido van Rossume905e952000-09-05 12:42:46 +0000919 += -= *= /= %= **= <<= >>= &= ^= |=
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000920
921For example,
922
923 A += B
924
925is similar to
926
927 A = A + B
928
929except that A is evaluated only once (relevant when A is something
930like dict[index].attr).
931
932However, if A is a mutable object, A may be modified in place. Thus,
933if A is a number or a string, A += B has the same effect as A = A+B
934(except A is only evaluated once); but if a is a list, A += B has the
935same effect as A.extend(B)!
936
937Classes and built-in object types can override the new operators in
938order to implement the in-place behavior; the not-in-place behavior is
939used automatically as a fallback when an object doesn't implement the
940in-place behavior. For classes, the method name is derived from the
941method name for the corresponding not-in-place operator by inserting
942an 'i' in front of the name, e.g. __iadd__ implements in-place
943__add__.
944
945Augmented assignment was implemented by Thomas Wouters.
946
947
948List Comprehensions
949-------------------
950
951This is a flexible new notation for lists whose elements are computed
952from another list (or lists). The simplest form is:
953
954 [<expression> for <variable> in <sequence>]
955
Guido van Rossum56db0952000-09-06 23:34:25 +0000956For example, [i**2 for i in range(4)] yields the list [0, 1, 4, 9].
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000957This is more efficient than a for loop with a list.append() call.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000958
959You can also add a condition:
960
961 [<expression> for <variable> in <sequence> if <condition>]
962
963For example, [w for w in words if w == w.lower()] would yield the list
964of words that contain no uppercase characters. This is more efficient
Guido van Rossumf62ed9c2000-09-26 11:16:10 +0000965than a for loop with an if statement and a list.append() call.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000966
967You can also have nested for loops and more than one 'if' clause. For
968example, here's a function that flattens a sequence of sequences::
969
970 def flatten(seq):
971 return [x for subseq in seq for x in subseq]
972
973 flatten([[0], [1,2,3], [4,5], [6,7,8,9], []])
974
975This prints
976
977 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
978
979List comprehensions originated as a patch set from Greg Ewing; Skip
Jeremy Hylton24c3d602000-09-05 19:36:26 +0000980Montanaro and Thomas Wouters also contributed. Described by PEP 202.
Guido van Rossumf2ffce02000-09-05 04:38:34 +0000981
982
983Extended Import Statement
984-------------------------
985
986Many people have asked for a way to import a module under a different
987name. This can be accomplished like this:
988
989 import foo
990 bar = foo
991 del foo
992
993but this common idiom gets old quickly. A simple extension of the
994import statement now allows this to be written as follows:
995
996 import foo as bar
997
998There's also a variant for 'from ... import':
999
1000 from foo import bar as spam
1001
1002This also works with packages; e.g. you can write this:
1003
1004 import test.regrtest as regrtest
1005
1006Note that 'as' is not a new keyword -- it is recognized only in this
1007context (this is only possible because the syntax for the import
1008statement doesn't involve expressions).
1009
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001010Implemented by Thomas Wouters. Described by PEP 221.
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001011
1012
1013Extended Print Statement
1014------------------------
1015
1016Easily the most controversial new feature, this extension to the print
1017statement adds an option to make the output go to a different file
1018than the default sys.stdout.
1019
1020For example, to write an error message to sys.stderr, you can now
1021write:
1022
1023 print >> sys.stderr, "Error: bad dog!"
1024
1025As a special feature, if the expression used to indicate the file
Fred Drake45888ff2000-09-29 17:09:11 +00001026evaluates to None, the current value of sys.stdout is used. Thus:
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001027
1028 print >> None, "Hello world"
1029
1030is equivalent to
1031
1032 print "Hello world"
1033
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001034Design and implementation by Barry Warsaw. Described by PEP 214.
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001035
1036
1037Optional Collection of Cyclical Garbage
1038---------------------------------------
1039
1040Python is now equipped with a garbage collector that can hunt down
1041cyclical references between Python objects. It's no replacement for
1042reference counting; in fact, it depends on the reference counts being
1043correct, and decides that a set of objects belong to a cycle if all
1044their reference counts can be accounted for from their references to
1045each other. This devious scheme was first proposed by Eric Tiedemann,
1046and brought to implementation by Neil Schemenauer.
1047
1048There's a module "gc" that lets you control some parameters of the
1049garbage collection. There's also an option to the configure script
1050that lets you enable or disable the garbage collection. In 2.0b1,
1051it's on by default, so that we (hopefully) can collect decent user
1052experience with this new feature. There are some questions about its
Fred Drake9f11cf82000-09-29 17:54:40 +00001053performance. If it proves to be too much of a problem, we'll turn it
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001054off by default in the final 2.0 release.
1055
1056
1057Smaller Changes
1058---------------
1059
1060A new function zip() was added. zip(seq1, seq2, ...) is equivalent to
1061map(None, seq1, seq2, ...) when the sequences have the same length;
1062i.e. zip([1,2,3], [10,20,30]) returns [(1,10), (2,20), (3,30)]. When
1063the lists are not all the same length, the shortest list wins:
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001064zip([1,2,3], [10,20]) returns [(1,10), (2,20)]. See PEP 201.
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001065
1066sys.version_info is a tuple (major, minor, micro, level, serial).
1067
1068Dictionaries have an odd new method, setdefault(key, default).
1069dict.setdefault(key, default) returns dict[key] if it exists; if not,
1070it sets dict[key] to default and returns that value. Thus:
1071
1072 dict.setdefault(key, []).append(item)
1073
1074does the same work as this common idiom:
1075
1076 if not dict.has_key(key):
1077 dict[key] = []
1078 dict[key].append(item)
1079
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001080There are two new variants of SyntaxError that are raised for
1081indentation-related errors: IndentationError and TabError.
1082
1083Changed \x to consume exactly two hex digits; see PEP 223. Added \U
1084escape that consumes exactly eight hex digits.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001085
1086The limits on the size of expressions and file in Python source code
1087have been raised from 2**16 to 2**32. Previous versions of Python
1088were limited because the maximum argument size the Python VM accepted
1089was 2**16. This limited the size of object constructor expressions,
1090e.g. [1,2,3] or {'a':1, 'b':2}, and the size of source files. This
1091limit was raised thanks to a patch by Charles Waldman that effectively
1092fixes the problem. It is now much more likely that you will be
1093limited by available memory than by an arbitrary limit in Python.
1094
1095The interpreter's maximum recursion depth can be modified by Python
1096programs using sys.getrecursionlimit and sys.setrecursionlimit. This
1097limit is the maximum number of recursive calls that can be made by
1098Python code. The limit exists to prevent infinite recursion from
1099overflowing the C stack and causing a core dump. The default value is
11001000. The maximum safe value for a particular platform can be found
1101by running Misc/find_recursionlimit.py.
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001102
1103New Modules and Packages
1104------------------------
1105
1106atexit - for registering functions to be called when Python exits.
1107
1108imputil - Greg Stein's alternative API for writing custom import
1109hooks.
1110
1111pyexpat - an interface to the Expat XML parser, contributed by Paul
1112Prescod.
1113
1114xml - a new package with XML support code organized (so far) in three
1115subpackages: xml.dom, xml.sax, and xml.parsers. Describing these
1116would fill a volume. There's a special feature whereby a
1117user-installed package named _xmlplus overrides the standard
1118xmlpackage; this is intended to give the XML SIG a hook to distribute
1119backwards-compatible updates to the standard xml package.
1120
1121webbrowser - a platform-independent API to launch a web browser.
1122
1123
Guido van Rossume905e952000-09-05 12:42:46 +00001124Changed Modules
1125---------------
1126
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001127array -- new methods for array objects: count, extend, index, pop, and
1128remove
1129
1130binascii -- new functions b2a_hex and a2b_hex that convert between
1131binary data and its hex representation
1132
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001133calendar -- Many new functions that support features including control
1134over which day of the week is the first day, returning strings instead
1135of printing them. Also new symbolic constants for days of week,
1136e.g. MONDAY, ..., SUNDAY.
1137
1138cgi -- FieldStorage objects have a getvalue method that works like a
1139dictionary's get method and returns the value attribute of the object.
1140
1141ConfigParser -- The parser object has new methods has_option,
1142remove_section, remove_option, set, and write. They allow the module
1143to be used for writing config files as well as reading them.
1144
1145ftplib -- ntransfercmd(), transfercmd(), and retrbinary() all now
Guido van Rossume905e952000-09-05 12:42:46 +00001146optionally support the RFC 959 REST command.
1147
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001148gzip -- readline and readlines now accept optional size arguments
Guido van Rossume905e952000-09-05 12:42:46 +00001149
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001150httplib -- New interfaces and support for HTTP/1.1 by Greg Stein. See
1151the module doc strings for details.
Guido van Rossum830ca2a2000-09-05 15:34:16 +00001152
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001153locale -- implement getdefaultlocale for Win32 and Macintosh
1154
1155marshal -- no longer dumps core when marshaling deeply nested or
1156recursive data structures
1157
1158os -- new functions isatty, seteuid, setegid, setreuid, setregid
1159
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001160os/popen2 -- popen2/popen3/popen4 support under Windows. popen2/popen3
1161support under Unix.
1162
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001163os/pty -- support for openpty and forkpty
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001164
1165os.path -- fix semantics of os.path.commonprefix
1166
1167smtplib -- support for sending very long messages
1168
1169socket -- new function getfqdn()
1170
1171readline -- new functions to read, write and truncate history files.
1172The readline section of the library reference manual contains an
1173example.
1174
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001175select -- add interface to poll system call
1176
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001177shutil -- new copyfileobj function
1178
1179SimpleHTTPServer, CGIHTTPServer -- Fix problems with buffering in the
1180HTTP server.
1181
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001182Tkinter -- optimization of function flatten
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001183
1184urllib -- scans environment variables for proxy configuration,
Tim Peters8b092332000-09-05 20:15:25 +00001185e.g. http_proxy.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001186
1187whichdb -- recognizes dumbdbm format
Guido van Rossume905e952000-09-05 12:42:46 +00001188
1189
1190Obsolete Modules
1191----------------
1192
1193None. However note that 1.6 made a whole slew of modules obsolete:
1194stdwin, soundex, cml, cmpcache, dircache, dump, find, grep, packmail,
1195poly, zmod, strop, util, whatsound.
1196
1197
1198Changed, New, Obsolete Tools
1199----------------------------
1200
Tim Peters8b092332000-09-05 20:15:25 +00001201None.
Guido van Rossume905e952000-09-05 12:42:46 +00001202
1203
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001204C-level Changes
1205---------------
1206
1207Several cleanup jobs were carried out throughout the source code.
1208
1209All C code was converted to ANSI C; we got rid of all uses of the
1210Py_PROTO() macro, which makes the header files a lot more readable.
1211
1212Most of the portability hacks were moved to a new header file,
1213pyport.h; several other new header files were added and some old
1214header files were removed, in an attempt to create a more rational set
1215of header files. (Few of these ever need to be included explicitly;
1216they are all included by Python.h.)
1217
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001218Trent Mick ensured portability to 64-bit platforms, under both Linux
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001219and Win64, especially for the new Intel Itanium processor. Mick also
1220added large file support for Linux64 and Win64.
Guido van Rossumf2ffce02000-09-05 04:38:34 +00001221
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001222The C APIs to return an object's size have been update to consistently
1223use the form PyXXX_Size, e.g. PySequence_Size and PyDict_Size. In
1224previous versions, the abstract interfaces used PyXXX_Length and the
1225concrete interfaces used PyXXX_Size. The old names,
1226e.g. PyObject_Length, are still available for backwards compatibility
1227at the API level, but are deprecated.
1228
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001229The PyOS_CheckStack function has been implemented on Windows by
1230Fredrik Lundh. It prevents Python from failing with a stack overflow
1231on Windows.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001232
1233The GC changes resulted in creation of two new slots on object,
1234tp_traverse and tp_clear. The augmented assignment changes result in
Guido van Rossum4338a282000-09-06 13:02:08 +00001235the creation of a new slot for each in-place operator.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001236
1237The GC API creates new requirements for container types implemented in
Guido van Rossum4338a282000-09-06 13:02:08 +00001238C extension modules. See Include/objimpl.h for details.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001239
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001240PyErr_Format has been updated to automatically calculate the size of
1241the buffer needed to hold the formatted result string. This change
1242prevents crashes caused by programmer error.
Jeremy Hyltonbdebd542000-09-05 18:28:54 +00001243
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001244New C API calls: PyObject_AsFileDescriptor, PyErr_WriteUnraisable.
Guido van Rossume905e952000-09-05 12:42:46 +00001245
Jeremy Hylton24c3d602000-09-05 19:36:26 +00001246PyRun_AnyFileEx, PyRun_SimpleFileEx, PyRun_FileEx -- New functions
1247that are the same as their non-Ex counterparts except they take an
1248extra flag argument that tells them to close the file when done.
1249
1250XXX There were other API changes that should be fleshed out here.
Guido van Rossumab9d6f01998-08-10 22:01:13 +00001251
Tim Peters8b092332000-09-05 20:15:25 +00001252
1253Windows Changes
1254---------------
1255
1256New popen2/popen3/peopen4 in os module (see Changed Modules above).
1257
1258os.popen is much more usable on Windows 95 and 98. See Microsoft
1259Knowledge Base article Q150956. The Win9x workaround described there
1260is implemented by the new w9xpopen.exe helper in the root of your
1261Python installation. Note that Python uses this internally; it is not
1262a standalone program.
1263
1264Administrator privileges are no longer required to install Python
1265on Windows NT or Windows 2000. If you have administrator privileges,
1266Python's registry info will be written under HKEY_LOCAL_MACHINE.
1267Otherwise the installer backs off to writing Python's registry info
Guido van Rossum4338a282000-09-06 13:02:08 +00001268under HKEY_CURRENT_USER. The latter is sufficient for all "normal"
Tim Peters8b092332000-09-05 20:15:25 +00001269uses of Python, but will prevent some advanced uses from working
1270(for example, running a Python script as an NT service, or possibly
1271from CGI).
1272
1273[This was new in 1.6] The installer no longer runs a separate Tcl/Tk
1274installer; instead, it installs the needed Tcl/Tk files directly in the
1275Python directory. If you already have a Tcl/Tk installation, this
1276wastes some disk space (about 4 Megs) but avoids problems with
1277conflicting Tcl/Tk installations, and makes it much easier for Python
1278to ensure that Tcl/Tk can find all its files.
1279
1280[This was new in 1.6] The Windows installer now installs by default in
1281\Python20\ on the default volume, instead of \Program Files\Python-2.0\.
1282
Guido van Rossumf62ed9c2000-09-26 11:16:10 +00001283
1284Updates to the changes between 1.5.2 and 1.6
1285--------------------------------------------
1286
1287The 1.6 NEWS file can't be changed after the release is done, so here
1288is some late-breaking news:
1289
1290New APIs in locale.py: normalize(), getdefaultlocale(), resetlocale(),
1291and changes to getlocale() and setlocale().
1292
1293The new module is now enabled per default.
1294
1295It is not true that the encodings codecs cannot be used for normal
1296strings: the string.encode() (which is also present on 8-bit strings
1297!) allows using them for 8-bit strings too, e.g. to convert files from
1298cp1252 (Windows) to latin-1 or vice-versa.
1299
1300Japanese codecs are available from Tamito KAJIYAMA:
1301http://pseudo.grad.sccs.chukyo-u.ac.jp/~kajiyama/python/
1302
1303
Guido van Rossumab9d6f01998-08-10 22:01:13 +00001304======================================================================