| What's New in Python 2.0b2? |
| =========================== |
| |
| Below is a list of all relevant changes since release 1.6. Older |
| changes are in the file HISTORY. If you are making the jump directly |
| from Python 1.5.2 to 2.0, make sure to read the section for 1.6 in the |
| HISTORY file! Many important changes listed there. |
| |
| Alternatively, a good overview of the changes between 1.5.2 and 2.0 is |
| the document "What's New in Python 2.0" by Kuchling and Moshe Zadka: |
| http://starship.python.net/crew/amk/python/writing/new-python/. |
| |
| --Guido van Rossum (home page: http://www.pythonlabs.com/~guido/) |
| |
| ====================================================================== |
| |
| |
| What's new in 2.0 beta 2 (since beta 1)? |
| ======================================== |
| |
| Core language, builtins, and interpreter |
| |
| - Add support for unbounded ints in %d,i,y,x,X,o formats for string |
| inter |
| |
| - Add -h and -V flags to print the usage message and Python version |
| number and exit immediately.polation. |
| |
| Standard library and extensions |
| |
| - array: reverse method of array now works. buffer_info now does |
| argument checking; it still takes no arguments. |
| |
| - asyncore/asynchat: included most recent version from Sam Rushing |
| |
| - cgi: accept & or ; as separate characters when parsing form data |
| |
| - CGIHTTPServer: now works on Windows (and perhaps even Mac). |
| |
| - ConfigParser: When reading the file, options spelled in upper case |
| letters are now accessible. |
| |
| - copy: Copy Unicode objects atomically. |
| |
| - cPickle: fails gracefully when copy_reg can't be imported |
| |
| - cStringIO: implemented readlines method. |
| |
| - dbm: Add set and setdefault methods to dbm object. Add constant |
| library to module that names the library used. Better doc strings |
| and argument checking. Uses configure to determine which ndbm.h |
| file to include; Berkeley DB's nbdm is now an option. |
| |
| - distutils: Update to version 0.9.3. |
| |
| - dl: Add several dl.RTLD_ constants. |
| |
| - fpectl: Now supported on FreeBSD. |
| |
| - gc: Add DEBUG_SAVEALL option. When enabled all garbage objects |
| found by the collector will be saved in gc.garbage. This is useful |
| for debugging a program that creates reference cycles. |
| |
| - httplib: Three changes. Restore support for set_debuglevel feature |
| of HTTP class. Do not close socket on zero-length response. Do not |
| crash when server sends invalid content-length header. |
| |
| - mailbox: XXX conformance to maildir specification ??? |
| |
| - operator: Add contains, invert, __invert__ as aliases for |
| __contains__, inv, and __inv__ respectively. |
| |
| - os: Add support for popen2 and popen3 on all platforms where fork |
| exists. |
| |
| - os: (Windows only) Add startfile function athat exposes part of |
| Win32 ShellExecute functionality. |
| |
| - os.path: (NT, DOS) Treat trailing colon correctly in os.path.join. |
| os.path.join("a:", "b") yields "a:b". |
| |
| - pickle: Now raises ValueError when an invalid pickle that contains |
| a non-string repr where a string repr was expected. This behavior |
| matches cPickle. |
| |
| - posixfile: XXX remove __del__ method ??? |
| |
| - py_compile: support \r in source file |
| |
| - readline: Does not immediately exit when ^C is hit when readline and |
| threads are configured. Adds defintion of rl_library_version. |
| |
| - rfc822: Domain literals returned by AddrlistClass method |
| getdomainliteral are now properly wrapped in brackets. |
| |
| - site: sys.setdefaultencoding() should only be called in case the |
| standard default encoding ("ascii") is changed. This safes quite a |
| few cycles during startup since the first call to |
| setdefaultencoding() will initialize the codec registry and the |
| encodings package. |
| |
| - socket: Support for size hint in readlines method of object returned |
| by makefile. |
| |
| - sre: Added experimental expand method to match objects. Does not |
| user buffer interface on Unicode strings. Does not hang if group id |
| is followed by whitespace. |
| |
| - StringIO: size hint in readlines is now supported as documented. |
| |
| - struct: Check ranges for bytes and shorts. |
| |
| - urllib: Improved handling of win32 proxy settings. Fixed quote and |
| quote_plus functions so that the always encode a comma ','. |
| |
| - Tkinter: Image objects are now guaranteed to have unique ids. Set |
| event.delta to zero if Tk version doesn't support mousewheel. |
| Removed some debugging prints. |
| |
| - UserList: now implements __contains__. |
| |
| - webbrower: On Windows, use os.startfile instead of os.popen, which |
| works around a bug in certain versions of Norton AntiVirus that |
| leads directly to a Blue Screen. |
| |
| - xml: New version detection code allows PyXML to override standard |
| XML package if PyXML version is greater than 0.6.1. |
| |
| - xml.dom: XXX |
| |
| - xml.sax: XXX |
| |
| - XXX pyexpat: XXX |
| |
| C API |
| |
| - Add three new convenience functions for module initialization -- |
| PyModule_AddObject(), PyModule_AddIntConstant(), and |
| PyModule_AddStringConstant(). |
| |
| - Cleaned up definition of NULL in C source code; all defintions were |
| removed and add #error to Python.h if NULL isn't defined after |
| #include of stdio.h. |
| |
| - Py_PROTO macros that were removed in 2.0b1 have been restored for |
| backwards compatibility (at the source level) with old extensions. |
| |
| - XXX PyOS_sighandler_t, PyOS_getsig, PyOS_setsig |
| |
| - Add PyString_AsStringAndSize call that provides access to the |
| internal data buffer and size of a string object -- or the default |
| encoded version of a Unicode object. |
| |
| Internals |
| |
| - On Unix, fix code for finding Python installation directory so that |
| it works when argv[0] is a relative path. |
| |
| - Added a true unicode_internal_encode function and fixed the |
| unicode_internal_decode function to support Unicode objects directly |
| rather than by generating a copy of the object. |
| |
| - XXX Unicode database compression |
| |
| Build and platform-specific issues |
| |
| - Better support of GNU Pth via --with-pth configure option. |
| |
| - Fix linker problems on Reliant UNIX |
| |
| - Changes for the benefit of SunOS 4.1.4 (really!). mmapmodule.c: |
| Don't define MS_SYNC to be zero when it is undefined. Added missing |
| prototypes in posixmodule.c. |
| |
| - Improved support for HP-UX build |
| |
| |
| What's new in 2.0 beta 1? |
| ========================= |
| |
| Source Incompatibilities |
| ------------------------ |
| |
| None. Note that 1.6 introduced several incompatibilities with 1.5.2, |
| such as single-argument append(), connect() and bind(), and changes to |
| str(long) and repr(float). |
| |
| |
| Binary Incompatibilities |
| ------------------------ |
| |
| - Third party extensions built for Python 1.5.x or 1.6 cannot be used |
| with Python 2.0; these extensions will have to be rebuilt for Python |
| 2.0. |
| |
| - On Windows, attempting to import a third party extension built for |
| Python 1.5.x or 1.6 results in an immediate crash; there's not much we |
| can do about this. Check your PYTHONPATH environment variable! |
| |
| - Python bytecode files (*.pyc and *.pyo) are not compatible between |
| releases. |
| |
| |
| Overview of Changes Since 1.6 |
| ----------------------------- |
| |
| There are many new modules (including brand new XML support through |
| the xml package, and i18n support through the gettext module); a list |
| of all new modules is included below. Lots of bugs have been fixed. |
| |
| The process for making major new changes to the language has changed |
| since Python 1.6. Enhancements must now be documented by a Python |
| Enhancement Proposal (PEP) before they can be accepted. |
| |
| There are several important syntax enhancements, described in more |
| detail below: |
| |
| - Augmented assignment, e.g. x += 1 |
| |
| - List comprehensions, e.g. [x**2 for x in range(10)] |
| |
| - Extended import statement, e.g. import Module as Name |
| |
| - Extended print statement, e.g. print >> file, "Hello" |
| |
| Other important changes: |
| |
| - Optional collection of cyclical garbage |
| |
| Python Enhancement Proposal (PEP) |
| --------------------------------- |
| |
| PEP stands for Python Enhancement Proposal. A PEP is a design |
| document providing information to the Python community, or describing |
| a new feature for Python. The PEP should provide a concise technical |
| specification of the feature and a rationale for the feature. |
| |
| We intend PEPs to be the primary mechanisms for proposing new |
| features, for collecting community input on an issue, and for |
| documenting the design decisions that have gone into Python. The PEP |
| author is responsible for building consensus within the community and |
| documenting dissenting opinions. |
| |
| The PEPs are available at http://python.sourceforge.net/peps/. |
| |
| Augmented Assignment |
| -------------------- |
| |
| This must have been the most-requested feature of the past years! |
| Eleven new assignment operators were added: |
| |
| += -= *= /= %= **= <<= >>= &= ^= |= |
| |
| For example, |
| |
| A += B |
| |
| is similar to |
| |
| A = A + B |
| |
| except that A is evaluated only once (relevant when A is something |
| like dict[index].attr). |
| |
| However, if A is a mutable object, A may be modified in place. Thus, |
| if A is a number or a string, A += B has the same effect as A = A+B |
| (except A is only evaluated once); but if a is a list, A += B has the |
| same effect as A.extend(B)! |
| |
| Classes and built-in object types can override the new operators in |
| order to implement the in-place behavior; the not-in-place behavior is |
| used automatically as a fallback when an object doesn't implement the |
| in-place behavior. For classes, the method name is derived from the |
| method name for the corresponding not-in-place operator by inserting |
| an 'i' in front of the name, e.g. __iadd__ implements in-place |
| __add__. |
| |
| Augmented assignment was implemented by Thomas Wouters. |
| |
| |
| List Comprehensions |
| ------------------- |
| |
| This is a flexible new notation for lists whose elements are computed |
| from another list (or lists). The simplest form is: |
| |
| [<expression> for <variable> in <sequence>] |
| |
| For example, [i**2 for i in range(4)] yields the list [0, 1, 4, 9]. |
| This is more efficient than map() with a lambda. |
| |
| You can also add a condition: |
| |
| [<expression> for <variable> in <sequence> if <condition>] |
| |
| For example, [w for w in words if w == w.lower()] would yield the list |
| of words that contain no uppercase characters. This is more efficient |
| than filter() with a lambda. |
| |
| You can also have nested for loops and more than one 'if' clause. For |
| example, here's a function that flattens a sequence of sequences:: |
| |
| def flatten(seq): |
| return [x for subseq in seq for x in subseq] |
| |
| flatten([[0], [1,2,3], [4,5], [6,7,8,9], []]) |
| |
| This prints |
| |
| [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] |
| |
| List comprehensions originated as a patch set from Greg Ewing; Skip |
| Montanaro and Thomas Wouters also contributed. Described by PEP 202. |
| |
| |
| Extended Import Statement |
| ------------------------- |
| |
| Many people have asked for a way to import a module under a different |
| name. This can be accomplished like this: |
| |
| import foo |
| bar = foo |
| del foo |
| |
| but this common idiom gets old quickly. A simple extension of the |
| import statement now allows this to be written as follows: |
| |
| import foo as bar |
| |
| There's also a variant for 'from ... import': |
| |
| from foo import bar as spam |
| |
| This also works with packages; e.g. you can write this: |
| |
| import test.regrtest as regrtest |
| |
| Note that 'as' is not a new keyword -- it is recognized only in this |
| context (this is only possible because the syntax for the import |
| statement doesn't involve expressions). |
| |
| Implemented by Thomas Wouters. Described by PEP 221. |
| |
| |
| Extended Print Statement |
| ------------------------ |
| |
| Easily the most controversial new feature, this extension to the print |
| statement adds an option to make the output go to a different file |
| than the default sys.stdout. |
| |
| For example, to write an error message to sys.stderr, you can now |
| write: |
| |
| print >> sys.stderr, "Error: bad dog!" |
| |
| As a special feature, if the expression used to indicate the file |
| evaluates to None, the current value of sys.stdout used. Thus: |
| |
| print >> None, "Hello world" |
| |
| is equivalent to |
| |
| print "Hello world" |
| |
| Design and implementation by Barry Warsaw. Described by PEP 214. |
| |
| |
| Optional Collection of Cyclical Garbage |
| --------------------------------------- |
| |
| Python is now equipped with a garbage collector that can hunt down |
| cyclical references between Python objects. It's no replacement for |
| reference counting; in fact, it depends on the reference counts being |
| correct, and decides that a set of objects belong to a cycle if all |
| their reference counts can be accounted for from their references to |
| each other. This devious scheme was first proposed by Eric Tiedemann, |
| and brought to implementation by Neil Schemenauer. |
| |
| There's a module "gc" that lets you control some parameters of the |
| garbage collection. There's also an option to the configure script |
| that lets you enable or disable the garbage collection. In 2.0b1, |
| it's on by default, so that we (hopefully) can collect decent user |
| experience with this new feature. There are some questions about its |
| performance. if it proves to be too much of a problem, we'll turn it |
| off by default in the final 2.0 release. |
| |
| |
| Smaller Changes |
| --------------- |
| |
| A new function zip() was added. zip(seq1, seq2, ...) is equivalent to |
| map(None, seq1, seq2, ...) when the sequences have the same length; |
| i.e. zip([1,2,3], [10,20,30]) returns [(1,10), (2,20), (3,30)]. When |
| the lists are not all the same length, the shortest list wins: |
| zip([1,2,3], [10,20]) returns [(1,10), (2,20)]. See PEP 201. |
| |
| sys.version_info is a tuple (major, minor, micro, level, serial). |
| |
| Dictionaries have an odd new method, setdefault(key, default). |
| dict.setdefault(key, default) returns dict[key] if it exists; if not, |
| it sets dict[key] to default and returns that value. Thus: |
| |
| dict.setdefault(key, []).append(item) |
| |
| does the same work as this common idiom: |
| |
| if not dict.has_key(key): |
| dict[key] = [] |
| dict[key].append(item) |
| |
| There are two new variants of SyntaxError that are raised for |
| indentation-related errors: IndentationError and TabError. |
| |
| Changed \x to consume exactly two hex digits; see PEP 223. Added \U |
| escape that consumes exactly eight hex digits. |
| |
| The limits on the size of expressions and file in Python source code |
| have been raised from 2**16 to 2**32. Previous versions of Python |
| were limited because the maximum argument size the Python VM accepted |
| was 2**16. This limited the size of object constructor expressions, |
| e.g. [1,2,3] or {'a':1, 'b':2}, and the size of source files. This |
| limit was raised thanks to a patch by Charles Waldman that effectively |
| fixes the problem. It is now much more likely that you will be |
| limited by available memory than by an arbitrary limit in Python. |
| |
| The interpreter's maximum recursion depth can be modified by Python |
| programs using sys.getrecursionlimit and sys.setrecursionlimit. This |
| limit is the maximum number of recursive calls that can be made by |
| Python code. The limit exists to prevent infinite recursion from |
| overflowing the C stack and causing a core dump. The default value is |
| 1000. The maximum safe value for a particular platform can be found |
| by running Misc/find_recursionlimit.py. |
| |
| New Modules and Packages |
| ------------------------ |
| |
| atexit - for registering functions to be called when Python exits. |
| |
| imputil - Greg Stein's alternative API for writing custom import |
| hooks. |
| |
| pyexpat - an interface to the Expat XML parser, contributed by Paul |
| Prescod. |
| |
| xml - a new package with XML support code organized (so far) in three |
| subpackages: xml.dom, xml.sax, and xml.parsers. Describing these |
| would fill a volume. There's a special feature whereby a |
| user-installed package named _xmlplus overrides the standard |
| xmlpackage; this is intended to give the XML SIG a hook to distribute |
| backwards-compatible updates to the standard xml package. |
| |
| webbrowser - a platform-independent API to launch a web browser. |
| |
| |
| Changed Modules |
| --------------- |
| |
| array -- new methods for array objects: count, extend, index, pop, and |
| remove |
| |
| binascii -- new functions b2a_hex and a2b_hex that convert between |
| binary data and its hex representation |
| |
| calendar -- Many new functions that support features including control |
| over which day of the week is the first day, returning strings instead |
| of printing them. Also new symbolic constants for days of week, |
| e.g. MONDAY, ..., SUNDAY. |
| |
| cgi -- FieldStorage objects have a getvalue method that works like a |
| dictionary's get method and returns the value attribute of the object. |
| |
| ConfigParser -- The parser object has new methods has_option, |
| remove_section, remove_option, set, and write. They allow the module |
| to be used for writing config files as well as reading them. |
| |
| ftplib -- ntransfercmd(), transfercmd(), and retrbinary() all now |
| optionally support the RFC 959 REST command. |
| |
| gzip -- readline and readlines now accept optional size arguments |
| |
| httplib -- New interfaces and support for HTTP/1.1 by Greg Stein. See |
| the module doc strings for details. |
| |
| locale -- implement getdefaultlocale for Win32 and Macintosh |
| |
| marshal -- no longer dumps core when marshaling deeply nested or |
| recursive data structures |
| |
| os -- new functions isatty, seteuid, setegid, setreuid, setregid |
| |
| os/popen2 -- popen2/popen3/popen4 support under Windows. popen2/popen3 |
| support under Unix. |
| |
| os/pty -- support for openpty and forkpty |
| |
| os.path -- fix semantics of os.path.commonprefix |
| |
| smtplib -- support for sending very long messages |
| |
| socket -- new function getfqdn() |
| |
| readline -- new functions to read, write and truncate history files. |
| The readline section of the library reference manual contains an |
| example. |
| |
| select -- add interface to poll system call |
| |
| shutil -- new copyfileobj function |
| |
| SimpleHTTPServer, CGIHTTPServer -- Fix problems with buffering in the |
| HTTP server. |
| |
| Tkinter -- optimization of function flatten |
| |
| urllib -- scans environment variables for proxy configuration, |
| e.g. http_proxy. |
| |
| whichdb -- recognizes dumbdbm format |
| |
| |
| Obsolete Modules |
| ---------------- |
| |
| None. However note that 1.6 made a whole slew of modules obsolete: |
| stdwin, soundex, cml, cmpcache, dircache, dump, find, grep, packmail, |
| poly, zmod, strop, util, whatsound. |
| |
| |
| Changed, New, Obsolete Tools |
| ---------------------------- |
| |
| None. |
| |
| |
| C-level Changes |
| --------------- |
| |
| Several cleanup jobs were carried out throughout the source code. |
| |
| All C code was converted to ANSI C; we got rid of all uses of the |
| Py_PROTO() macro, which makes the header files a lot more readable. |
| |
| Most of the portability hacks were moved to a new header file, |
| pyport.h; several other new header files were added and some old |
| header files were removed, in an attempt to create a more rational set |
| of header files. (Few of these ever need to be included explicitly; |
| they are all included by Python.h.) |
| |
| Trent Mick ensured portability to 64-bit platforms, under both Linux |
| and Win64, especially for the new Intel Itanium processor. Mick also |
| added large file support for Linux64 and Win64. |
| |
| The C APIs to return an object's size have been update to consistently |
| use the form PyXXX_Size, e.g. PySequence_Size and PyDict_Size. In |
| previous versions, the abstract interfaces used PyXXX_Length and the |
| concrete interfaces used PyXXX_Size. The old names, |
| e.g. PyObject_Length, are still available for backwards compatibility |
| at the API level, but are deprecated. |
| |
| The PyOS_CheckStack function has been implemented on Windows by |
| Fredrik Lundh. It prevents Python from failing with a stack overflow |
| on Windows. |
| |
| The GC changes resulted in creation of two new slots on object, |
| tp_traverse and tp_clear. The augmented assignment changes result in |
| the creation of a new slot for each in-place operator. |
| |
| The GC API creates new requirements for container types implemented in |
| C extension modules. See Include/objimpl.h for details. |
| |
| PyErr_Format has been updated to automatically calculate the size of |
| the buffer needed to hold the formatted result string. This change |
| prevents crashes caused by programmer error. |
| |
| New C API calls: PyObject_AsFileDescriptor, PyErr_WriteUnraisable. |
| |
| PyRun_AnyFileEx, PyRun_SimpleFileEx, PyRun_FileEx -- New functions |
| that are the same as their non-Ex counterparts except they take an |
| extra flag argument that tells them to close the file when done. |
| |
| XXX There were other API changes that should be fleshed out here. |
| |
| |
| Windows Changes |
| --------------- |
| |
| New popen2/popen3/peopen4 in os module (see Changed Modules above). |
| |
| os.popen is much more usable on Windows 95 and 98. See Microsoft |
| Knowledge Base article Q150956. The Win9x workaround described there |
| is implemented by the new w9xpopen.exe helper in the root of your |
| Python installation. Note that Python uses this internally; it is not |
| a standalone program. |
| |
| Administrator privileges are no longer required to install Python |
| on Windows NT or Windows 2000. If you have administrator privileges, |
| Python's registry info will be written under HKEY_LOCAL_MACHINE. |
| Otherwise the installer backs off to writing Python's registry info |
| under HKEY_CURRENT_USER. The latter is sufficient for all "normal" |
| uses of Python, but will prevent some advanced uses from working |
| (for example, running a Python script as an NT service, or possibly |
| from CGI). |
| |
| [This was new in 1.6] The installer no longer runs a separate Tcl/Tk |
| installer; instead, it installs the needed Tcl/Tk files directly in the |
| Python directory. If you already have a Tcl/Tk installation, this |
| wastes some disk space (about 4 Megs) but avoids problems with |
| conflicting Tcl/Tk installations, and makes it much easier for Python |
| to ensure that Tcl/Tk can find all its files. |
| |
| [This was new in 1.6] The Windows installer now installs by default in |
| \Python20\ on the default volume, instead of \Program Files\Python-2.0\. |
| |
| ====================================================================== |