Python history

--------------

This file contains the release messages for previous Python releases

(slightly edited to adapt them to the format of this file). As you

read on you go back to the dark ages of Python's history.

=====================================

==> Release 1.3 (13 October 1995) <==

=====================================

Major change

============

Two words: Keyword Arguments. See the first section of Chapter 12 of

the Tutorial.

(The rest of this file is textually the same as the remaining sections

of that chapter.)

Changes to the WWW and Internet tools

=====================================

The "htmllib" module has been rewritten in an incompatible fashion.

The new version is considerably more complete (HTML 2.0 except forms,

but including all ISO-8859-1 entity definitions), and easy to use.

Small changes to "sgmllib" have also been made, to better match the

tokenization of HTML as recognized by other web tools.

A new module "formatter" has been added, for use with the new

"htmllib" module.

The "urllib"and "httplib" modules have been changed somewhat to allow

overriding unknown URL types and to support authentication. They now

use "mimetools.Message" instead of "rfc822.Message" to parse headers.

The "endrequest()" method has been removed from the HTTP class since

it breaks the interaction with some servers.

The "rfc822.Message" class has been changed to allow a flag to be

passed in that says that the file is unseekable.

The "ftplib" module has been fixed to be (hopefully) more robust on

Linux.

Several new operations that are optionally supported by servers have

been added to "nntplib": "xover", "xgtitle", "xpath" and "date".

Other Language Changes

======================

The "raise" statement now takes an optional argument which specifies

the traceback to be used when printing the exception's stack trace.

This must be a traceback object, such as found in "sys.exc_traceback".

When omitted or given as "None", the old behavior (to generate a stack

trace entry for the current stack frame) is used.

The tokenizer is now more tolerant of alien whitespace. Control-L in

the leading whitespace of a line resets the column number to zero,

while Control-R just before the end of the line is ignored.

Changes to Built-in Operations

==============================

For file objects, "f.read(0)" and "f.readline(0)" now return an empty

string rather than reading an unlimited number of bytes. For the

latter, omit the argument altogether or pass a negative value.

A new system variable, "sys.platform", has been added. It specifies

the current platform, e.g. "sunos5" or "linux1".

The built-in functions "input()" and "raw_input()" now use the GNU

readline library when it has been configured (formerly, only

interactive input to the interpreter itself was read using GNU

readline). The GNU readline library provides elaborate line editing

and history. The Python debugger ("pdb") is the first beneficiary of

this change.

Two new built-in functions, "globals()" and "locals()", provide access

to dictionaries containming current global and local variables,

respectively. (These augment rather than replace "vars()", which

returns the current local variables when called without an argument,

and a module's global variables when called with an argument of type

module.)

The built-in function "compile()" now takes a third possible value for

the kind of code to be compiled: specifying "'single'" generates code

for a single interactive statement, which prints the output of

expression statements that evaluate to something else than "None".

Library Changes

===============

There are new module "ni" and "ihooks" that support importing modules

with hierarchical names such as "A.B.C". This is enabled by writing

"import ni; ni.ni()" at the very top of the main program. These

modules are amply documented in the Python source.

The module "rexec" has been rewritten (incompatibly) to define a class

and to use "ihooks".

The "string.split()" and "string.splitfields()" functions are now the

same function (the presence or absence of the second argument

determines which operation is invoked); similar for "string.join()"

and "string.joinfields()".

The "Tkinter" module and its helper "Dialog" have been revamped to use

keyword arguments. Tk 4.0 is now the standard. A new module

"FileDialog" has been added which implements standard file selection

dialogs.

The optional built-in modules "dbm" and "gdbm" are more coordinated

--- their "open()" functions now take the same values for their "flag"

argument, and the "flag" and "mode" argument have default values (to

open the database for reading only, and to create the database with

mode "0666" minuse the umask, respectively). The memory leaks have

finally been fixed.

A new dbm-like module, "bsddb", has been added, which uses the BSD DB

package's hash method.

A portable (though slow) dbm-clone, implemented in Python, has been

added for systems where none of the above is provided. It is aptly

dubbed "dumbdbm".

The module "anydbm" provides a unified interface to "bsddb", "gdbm",

"dbm", and "dumbdbm", choosing the first one available.

A new extension module, "binascii", provides a variety of operations

for conversion of text-encoded binary data.

There are three new or rewritten companion modules implemented in

Python that can encode and decode the most common such formats: "uu"

(uuencode), "base64" and "binhex".

A module to handle the MIME encoding quoted-printable has also been

added: "quopri".

The parser module (which provides an interface to the Python parser's

abstract syntax trees) has been rewritten (incompatibly) by Fred

Drake. It now lets you change the parse tree and compile the result!

The \code{syslog} module has been upgraded and documented.

Other Changes

=============

The dynamic module loader recognizes the fact that different filenames

point to the same shared library and loads the library only once, so

you can have a single shared library that defines multiple modules.

(SunOS / SVR4 style shared libraries only.)

Jim Fulton's ``abstract object interface'' has been incorporated into

the run-time API. For more detailes, read the files

"Include/abstract.h" and "Objects/abstract.c".

The Macintosh version is much more robust now.

Numerous things I have forgotten or that are so obscure no-one will

notice them anyway :-)

===================================

==> Release 1.2 (13 April 1995) <==

===================================

- Changes to Misc/python-mode.el:

- Wrapping and indentation within triple quote strings should work

properly now.

- `Standard' bug reporting mechanism (use C-c C-b)

- py-mark-block was moved to C-c C-m

- C-c C-v shows you the python-mode version

- a basic python-font-lock-keywords has been added for Emacs 19

font-lock colorizations.

- proper interaction with pending-del and del-sel modes.

- New py-electric-colon (:) command for improved outdenting. Also

py-indent-line (TAB) should handle outdented lines better.

- New commands py-outdent-left (C-c C-l) and py-indent-right (C-c C-r)

- The Library Reference has been restructured, and many new and

existing modules are now documented, in particular the debugger and

the profiler, as well as the persistency and the WWW/Internet support

modules.

- All known bugs have been fixed. For example the pow(2,2,3L) bug on

Linux has been fixed. Also the re-entrancy problems with __del__ have

been fixed.

- All known memory leaks have been fixed.

- Phase 2 of the Great Renaming has been executed. The header files

now use the new names (PyObject instead of object, etc.). The linker

also sees the new names. Most source files still use the old names,

by virtue of the rename2.h header file. If you include Python.h, you

only see the new names. Dynamically linked modules have to be

recompiled. (Phase 3, fixing the rest of the sources, will be

executed gradually with the release later versions.)

- The hooks for implementing "safe-python" (better called "restricted

execution") are in place. Specifically, the import statement is

implemented by calling the built-in function __import__, and the

built-in names used in a particular scope are taken from the

dictionary __builtins__ in that scope's global dictionary. See also

the new (unsupported, undocumented) module rexec.py.

- The import statement now supports the syntax "import a.b.c" and

"from a.b.c import name". No officially supported implementation

exists, but one can be prototyped by replacing the built-in __import__

function. A proposal by Ken Manheimer is provided as newimp.py.

- All machinery used by the import statement (or the built-in

__import__ function) is now exposed through the new built-in module

"imp" (see the library reference manual). All dynamic loading

machinery is moved to the new file importdl.c.

- Persistent storage is supported through the use of the modules

"pickle" and "shelve" (implemented in Python). There's also a "copy"

module implementing deepcopy and normal (shallow) copy operations.

See the library reference manual.

- Documentation strings for many objects types are accessible through

the __doc__ attribute. Modules, classes and functions support special

syntax to initialize the __doc__ attribute: if the first statement

consists of just a string literal, that string literal becomes the

value of the __doc__ attribute. The default __doc__ attribute is

None. Documentation strings are also supported for built-in

functions, types and modules; however this feature hasn't been widely

used yet. See the 'new' module for an example. (Basically, the type

object's tp_doc field contains the doc string for the type, and the

4th member of the methodlist structure contains the doc string for the

method.)

- The __coerce__ and __cmp__ methods for user-defined classes once

again work as expected. As an example, there's a new standard class

Complex in the library.

- The functions posix.popen() and posix.fdopen() now have an optional

third argument to specify the buffer size, and default their second

(mode) argument to 'r' -- in analogy to the builtin open() function.

The same applies to posixfile.open() and the socket method makefile().

- The thread.exit_thread() function now raises SystemExit so that

'finally' clauses are honored and a memory leak is plugged.

- Improved X11 and Motif support, by Sjoerd Mullender. This extension

is being maintained and distributed separately.

- Improved support for the Apple Macintosh, in part by Jack Jansen,

e.g. interfaces to (a few) resource mananger functions, get/set file

type and creator, gestalt, sound manager, speech manager, MacTCP, comm

toolbox, and the think C console library. This is being maintained

and distributed separately.

- Improved version for Windows NT, by Mark Hammond. This is being

maintained and distributed separately.

- Used autoconf 2.0 to generate the configure script. Adapted

configure.in to use the new features in autoconf 2.0.

- It now builds on the NeXT without intervention, even on the 3.3

Sparc pre-release.

- Characters passed to isspace() and friends are masked to nonnegative

values.

- Correctly compute pow(-3.0, 3).

- Fix portability problems with getopt (configure now checks for a

non-GNU getopt).

- Don't add frozenmain.o to libPython.a.

- Exceptions can now be classes. ALl built-in exceptions are still

string objects, but this will change in the future.

- The socket module exports a long list of socket related symbols.

(More built-in modules will export their symbolic constants instead of

relying on a separately generated Python module.)

- When a module object is deleted, it clears out its own dictionary.

This fixes a circularity in the references between functions and

their global dictionary.

- Changed the error handling by [new]getargs() e.g. for "O&".

- Dynamic loading of modules using shared libraries is supported for

several new platforms.

- Support "O&", "[...]" and "{...}" in mkvalue().

- Extension to findmethod(): findmethodinchain() (where a chain is a

linked list of methodlist arrays). The calling interface for

findmethod() has changed: it now gets a pointer to the (static!)

methodlist structure rather than just to the function name -- this

saves copying flags etc. into the (short-lived) method object.

- The callable() function is now public.

- Object types can define a few new operations by setting function

pointers in the type object structure: tp_call defines how an object

is called, and tp_str defines how an object's str() is computed.

===================================

==> Release 1.1.1 (10 Nov 1994) <==

===================================

This is a pure bugfix release again. See the ChangeLog file for details.

One exception: a few new features were added to tkinter.

=================================

==> Release 1.1 (11 Oct 1994) <==

=================================

This release adds several new features, improved configuration and

portability, and fixes more bugs than I can list here (including some

memory leaks).

The source compiles and runs out of the box on more platforms than

ever -- including Windows NT. Makefiles or projects for a variety of

non-UNIX platforms are provided.

APOLOGY: some new features are badly documented or not at all. I had

the choice -- postpone the new release indefinitely, or release it

now, with working code but some undocumented areas. The problem with

postponing the release is that people continue to suffer from existing

bugs, and send me patches based on the previous release -- which I

can't apply directly because my own source has changed. Also, some

new modules (like signal) have been ready for release for quite some

time, and people are anxiously waiting for them. In the case of

signal, the interface is simple enough to figure out without

documentation (if you're anxious enough :-). In this case it was not

simple to release the module on its own, since it relies on many small

patches elsewhere in the source.

For most new Python modules, the source code contains comments that

explain how to use them. Documentation for the Tk interface, written

by Matt Conway, is available as tkinter-doc.tar.gz from the Python

home and mirror ftp sites (see Misc/FAQ for ftp addresses). For the

new operator overloading facilities, have a look at Demo/classes:

Complex.py and Rat.py show how to implement a numeric type without and

with __coerce__ method. Also have a look at the end of the Tutorial

document (Doc/tut.tex). If you're still confused: use the newsgroup

or mailing list.

New language features:

- More flexible operator overloading for user-defined classes

(INCOMPATIBLE WITH PREVIOUS VERSIONS!) See end of tutorial.

- Classes can define methods named __getattr__, __setattr__ and

__delattr__ to trap attribute accesses. See end of tutorial.

- Classes can define method __call__ so instances can be called

directly. See end of tutorial.

New support facilities:

- The Makefiles (for the base interpreter as well as for extensions)

now support creating dynamically loadable modules if the platform

supports shared libraries.

- Passing the interpreter a .pyc file as script argument will execute

the code in that file. (On the Mac such files can be double-clicked!)

- New Freeze script, to create independently distributable "binaries"

of Python programs -- look in Demo/freeze

- Improved h2py script (in Demo/scripts) follows #includes and

supports macros with one argument

- New module compileall generates .pyc files for all modules in a

directory (tree) without also executing them

- Threads should work on more platforms

New built-in modules:

- tkinter (support for Tcl's Tk widget set) is now part of the base

distribution

- signal allows catching or ignoring UNIX signals (unfortunately still

undocumented -- any taker?)

- termios provides portable access to POSIX tty settings

- curses provides an interface to the System V curses library

- syslog provides an interface to the (BSD?) syslog daemon

- 'new' provides interfaces to create new built-in object types

(e.g. modules and functions)

- sybase provides an interface to SYBASE database

New/obsolete built-in methods:

- callable(x) tests whether x can be called

- sockets now have a setblocking() method

- sockets no longer have an allowbroadcast() method

- socket methods send() and sendto() return byte count

New standard library modules:

- types.py defines standard names for built-in types, e.g. StringType

- urlparse.py parses URLs according to the latest Internet draft

- uu.py does uuencode/uudecode (not the fastest in the world, but

quicker than installing uuencode on a non-UNIX machine :-)

- New, faster and more powerful profile module.py

- mhlib.py provides interface to MH folders and messages

New facilities for extension writers (unfortunately still

undocumented):

- newgetargs() supports optional arguments and improved error messages

- O!, O& O? formats for getargs allow more versatile type checking of

non-standard types

- can register pending asynchronous callback, to be called the next

time the Python VM begins a new instruction (Py_AddPendingCall)

- can register cleanup routines to be called when Python exits

(Py_AtExit)

- makesetup script understands C++ files in Setup file (use file.C

or file.cc)

- Make variable OPT is passed on to sub-Makefiles

- An init<module>() routine may signal an error by not entering

the module in the module table and raising an exception instead

- For long module names, instead of foobarbletchmodule.c you can

use foobarbletch.c

- getintvalue() and getfloatvalue() try to convert any object

instead of requiring an "intobject" or "floatobject"

- All the [new]getargs() formats that retrieve an integer value

will now also work if a float is passed

- C function listtuple() converts list to tuple, fast

- You should now call sigcheck() instead of intrcheck();

sigcheck() also sets an exception when it returns nonzero

====================================

==> Release 1.0.3 (14 July 1994) <==

====================================

This release consists entirely of bug fixes to the C sources; see the

head of ../ChangeLog for a complete list. Most important bugs fixed:

- Sometimes the format operator (string%expr) would drop the last

character of the format string

- Tokenizer looped when last line did not end in \n

- Bug when triple-quoted string ended in quote plus newline

- Typo in socketmodule (listen) (== instead of =)

- typing vars() at the >>> prompt would cause recursive output

==================================

==> Release 1.0.2 (4 May 1994) <==

==================================

Overview of the most visible changes. Bug fixes are not listed. See

also ChangeLog.

Tokens

------

* String literals follow Standard C rules: they may be continued on

the next line using a backslash; adjacent literals are concatenated

at compile time.

* A new kind of string literals, surrounded by triple quotes (""" or

'''), can be continued on the next line without a backslash.

Syntax

------

* Function arguments may have a default value, e.g. def f(a, b=1);

defaults are evaluated at function definition time. This also applies

to lambda.

* The try-except statement has an optional else clause, which is

executed when no exception occurs in the try clause.

Interpreter

-----------

* The result of a statement-level expression is no longer printed,

except_ for expressions entered interactively. Consequently, the -k

command line option is gone.

* The result of the last printed interactive expression is assigned to

the variable '_'.

* Access to implicit global variables has been speeded up by removing

an always-failing dictionary lookup in the dictionary of local

variables (mod suggested by Steve Makewski and Tim Peters).

* There is a new command line option, -u, to force stdout and stderr

to be unbuffered.

* Incorporated Steve Majewski's mods to import.c for dynamic loading

under AIX.

* Fewer chances of dumping core when trying to reload or re-import

static built-in, dynamically loaded built-in, or frozen modules.

* Loops over sequences now don't ask for the sequence's length when

they start, but try to access items 0, 1, 2, and so on until they hit

an IndexError. This makes it possible to create classes that generate

infinite or indefinite sequences a la Steve Majewski. This affects

for loops, the (not) in operator, and the built-in functions filter(),

map(), max(), min(), reduce().

Changed Built-in operations

---------------------------

* The '%' operator on strings (printf-style formatting) supports a new

feature (adapted from a patch by Donald Beaudry) to allow

'%(<key>)<format>' % {...} to take values from a dictionary by name

instead of from a tuple by position (see also the new function

vars()).

* The '%s' formatting operator is changed to accept any type and

convert it to a string using str().

* Dictionaries with more than 20,000 entries can now be created

(thanks to Steve Kirsch).

New Built-in Functions

----------------------

* vars() returns a dictionary containing the local variables; vars(m)

returns a dictionary containing the variables of module m. Note:

dir(x) is now equivalent to vars(x).keys().

Changed Built-in Functions

--------------------------

* open() has an optional third argument to specify the buffer size: 0

for unbuffered, 1 for line buffered, >1 for explicit buffer size, <0

for default.

* open()'s second argument is now optional; it defaults to "r".

* apply() now checks that its second argument is indeed a tuple.

New Built-in Modules

--------------------

Changed Built-in Modules

------------------------

The thread module no longer supports exit_prog().

New Python Modules

------------------

* Module addpack contains a standard interface to modify sys.path to

find optional packages (groups of related modules).

* Module urllib contains a number of functions to access

World-Wide-Web files specified by their URL.

* Module httplib implements the client side of the HTTP protocol used

by World-Wide-Web servers.

* Module gopherlib implements the client side of the Gopher protocol.

* Module mailbox (by Jack Jansen) contains a parser for UNIX and MMDF

style mailbox files.

* Module random contains various random distributions, e.g. gauss().

* Module lockfile locks and unlocks open files using fcntl (inspired

by a similar module by Andy Bensky).

* Module ntpath (by Jaap Vermeulen) implements path operations for

Windows/NT.

* Module test_thread (in Lib/test) contains a small test set for the

thread module.

Changed Python Modules

----------------------

* The string module's expandvars() function is now documented and is

implemented in Python (using regular expressions) instead of forking

off a shell process.

* Module rfc822 now supports accessing the header fields using the

mapping/dictionary interface, e.g. h['subject'].

* Module pdb now makes it possible to set a break on a function

(syntax: break <expression>, where <expression> yields a function

object).

Changed Demos

-------------

* The Demo/scripts/freeze.py script is working again (thanks to Jaap

Vermeulen).

New Demos

---------

* Demo/threads/Generator.py is a proposed interface for restartable

functions a la Tim Peters.

* Demo/scripts/newslist.py, by Quentin Stafford-Fraser, generates a

directory full of HTML pages which between them contain links to all

the newsgroups available on your server.

* Demo/dns contains a DNS (Domain Name Server) client.

* Demo/lutz contains miscellaneous demos by Mark Lutz (e.g. psh.py, a

nice enhanced Python shell!!!).

* Demo/turing contains a Turing machine by Amrit Prem.

Documentation

-------------

* Documented new language features mentioned above (but not all new

modules).

* Added a chapter to the Tutorial describing recent additions to

Python.

* Clarified some sentences in the reference manual,

e.g. break/continue, local/global scope, slice assignment.

Source Structure

----------------

* Moved Include/tokenizer.h to Parser/tokenizer.h.

* Added Python/getopt.c for systems that don't have it.

Emacs mode

----------

* Indentation of continuated lines is done more intelligently;

consequently the variable py-continuation-offset is gone.

========================================

==> Release 1.0.1 (15 February 1994) <==

========================================

* Many portability fixes should make it painless to build Python on

several new platforms, e.g. NeXT, SEQUENT, WATCOM, DOS, and Windows.

* Fixed test for <stdarg.h> -- this broke on some platforms.

* Fixed test for shared library dynalic loading -- this broke on SunOS

4.x using the GNU loader.

* Changed order and number of SVR4 networking libraries (it is now

-lsocket -linet -lnsl, if these libraries exist).

* Installing the build intermediate stages with "make libainstall" now

also installs config.c.in, Setup and makesetup, which are used by the

new Extensions mechanism.

* Improved README file contains more hints and new troubleshooting

section.

* The built-in module strop now defines fast versions of three more

functions of the standard string module: atoi(), atol() and atof().

The strop versions of atoi() and atol() support an optional second

argument to specify the base (default 10). NOTE: you don't have to

explicitly import strop to use the faster versions -- the string

module contains code to let versions from stop override the default

versions.

* There is now a working Lib/dospath.py for those who use Python under

DOS (or Windows). Thanks, Jaap!

* There is now a working Modules/dosmodule.c for DOS (or Windows)

system calls.

* Lib.os.py has been reorganized (making it ready for more operating

systems).

* Lib/ospath.py is now obsolete (use os.path instead).

* Many fixes to the tutorial to make it match Python 1.0. Thanks,

Tim!

* Fixed Doc/Makefile, Doc/README and various scripts there.

* Added missing description of fdopen to Doc/libposix.tex.

* Made cleanup() global, for the benefit of embedded applications.

* Added parsing of addresses and dates to Lib/rfc822.py.

* Small fixes to Lib/aifc.py, Lib/sunau.py, Lib/tzparse.py to make

them usable at all.

* New module Lib/wave.py reads RIFF (*.wav) audio files.

* Module Lib/filewin.py moved to Lib/stdwin/filewin.py where it

belongs.

* New options and comments for Modules/makesetup (used by new

Extension mechanism).

* Misc/HYPE contains text of announcement of 1.0.0 in comp.lang.misc

and elsewhere.

* Fixed coredump in filter(None, 'abcdefg').

=======================================

==> Release 1.0.0 (26 January 1994) <==

=======================================

As is traditional, so many things have changed that I can't pretend to

be complete in these release notes, but I'll try anyway :-)

Note that the very last section is labeled "remaining bugs".

Source organization and build process

-------------------------------------

* The sources have finally been split: instead of a single src

subdirectory there are now separate directories Include, Parser,

Grammar, Objects, Python and Modules. Other directories also start

with a capital letter: Misc, Doc, Lib, Demo.

* A few extensions (notably Amoeba and X support) have been moved to a

separate subtree Extensions, which is no longer in the core

distribution, but separately ftp'able as extensions.tar.Z. (The

distribution contains a placeholder Ext-dummy with a description of

the Extensions subtree as well as the most recent versions of the

scripts used there.)

* A few large specialized demos (SGI video and www) have been

moved to a separate subdirectory Demo2, which is no longer in the core

distribution, but separately ftp'able as demo2.tar.Z.

* Parts of the standard library have been moved to subdirectories:

there are now standard subdirectories stdwin, test, sgi and sun4.

* The configuration process has radically changed: I now use GNU

autoconf. This makes it much easier to build on new Unix flavors, as

well as fully supporting VPATH (if your Make has it). The scripts

Configure.py and Addmodule.sh are no longer needed. Many source files

have been adapted in order to work with the symbols that the configure

script generated by autoconf defines (or not); the resulting source is

much more portable to different C compilers and operating systems,

even non Unix systems (a Mac port was done in an afternoon). See the

toplevel README file for a description of the new build process.

* GNU readline (a slightly newer version) is now a subdirectory of the

Python toplevel. It is still not automatically configured (being

totally autoconf-unaware :-). One problem has been solved: typing

Control-C to a readline prompt will now work. The distribution no

longer contains a "super-level" directory (above the python toplevel

directory), and dl, dl-dld and GNU dld are no longer part of the

Python distribution (you can still ftp them from

ftp.cwi.nl:/pub/dynload).

* The DOS functions have been taken out of posixmodule.c and moved

into a separate file dosmodule.c.

* There's now a separate file version.c which contains nothing but

the version number.

* The actual main program is now contained in config.c (unless NO_MAIN

is defined); pythonmain.c now contains a function realmain() which is

called from config.c's main().

* All files needed to use the built-in module md5 are now contained in

the distribution. The module has been cleaned up considerably.

Documentation

-------------

* The library manual has been split into many more small latex files,

so it is easier to edit Doc/lib.tex file to create a custom library

manual, describing only those modules supported on your system. (This

is not automated though.)

* A fourth manual has been added, titled "Extending and Embedding the

Python Interpreter" (Doc/ext.tex), which collects information about

the interpreter which was previously spread over several files in the

misc subdirectory.

* The entire documentation is now also available on-line for those who

have a WWW browser (e.g. NCSA Mosaic). Point your browser to the URL

"http://www.cwi.nl/~guido/Python.html".

Syntax

------

* Strings may now be enclosed in double quotes as well as in single

quotes. There is no difference in interpretation. The repr() of

string objects will use double quotes if the string contains a single

quote and no double quotes. Thanks to Amrit Prem for these changes!

* There is a new keyword 'exec'. This replaces the exec() built-in

function. If a function contains an exec statement, local variable

optimization is not performed for that particular function, thus

making assignment to local variables in exec statements less

confusing. (As a consequence, os.exec and python.exec have been

renamed to execv.)

* There is a new keyword 'lambda'. An expression of the form

lambda <parameters> : <expression>

yields an anonymous function. This is really only syntactic sugar;

you can just as well define a local function using

def some_temporary_name(<parameters>): return <expression>

Lambda expressions are particularly useful in combination with map(),

filter() and reduce(), described below. Thanks to Amrit Prem for

submitting this code (as well as map(), filter(), reduce() and

xrange())!

Built-in functions

------------------

* The built-in module containing the built-in functions is called

__builtin__ instead of builtin.

* New built-in functions map(), filter() and reduce() perform standard

functional programming operations (though not lazily):

- map(f, seq) returns a new sequence whose items are the items from

seq with f() applied to them.

- filter(f, seq) returns a subsequence of seq consisting of those

items for which f() is true.

- reduce(f, seq, initial) returns a value computed as follows:

acc = initial

for item in seq: acc = f(acc, item)

return acc

* New function xrange() creates a "range object". Its arguments are

the same as those of range(), and when used in a for loop a range

objects also behaves identical. The advantage of xrange() over

range() is that its representation (if the range contains many

elements) is much more compact than that of range(). The disadvantage

is that the result cannot be used to initialize a list object or for

the "Python idiom" [RED, GREEN, BLUE] = range(3). On some modern

architectures, benchmarks have shown that "for i in range(...): ..."

actually executes *faster* than "for i in xrange(...): ...", but on

memory starved machines like PCs running DOS range(100000) may be just

too big to be represented at all...

* Built-in function exec() has been replaced by the exec statement --

see above.

The interpreter

---------------

* Syntax errors are now not printed to stderr by the parser, but

rather the offending line and other relevant information are packed up

in the SyntaxError exception argument. When the main loop catches a

SyntaxError exception it will print the error in the same format as

previously, but at the proper position in the stack traceback.

* You can now set a maximum to the number of traceback entries

printed by assigning to sys.tracebacklimit. The default is 1000.

* The version number in .pyc files has changed yet again.

* It is now possible to have a .pyc file without a corresponding .py

file. (Warning: this may break existing installations if you have an

old .pyc file lingering around somewhere on your module search path

without a corresponding .py file, when there is a .py file for a

module of the same name further down the path -- the new interpreter

will find the first .pyc file and complain about it, while the old

interpreter would ignore it and use the .py file further down.)

* The list sys.builtin_module_names is now sorted and also contains

the names of a few hardwired built-in modules (sys, __main__ and

__builtin__).

* A module can now find its own name by accessing the global variable

__name__. Assigning to this variable essentially renames the module

(it should also be stored under a different key in sys.modules).

A neat hack follows from this: a module that wants to execute a main

program when called as a script no longer needs to compare

sys.argv[0]; it can simply do "if __name__ == '__main__': main()".

* When an object is printed by the print statement, its implementation

of str() is used. This means that classes can define __str__(self) to

direct how their instances are printed. This is different from

__repr__(self), which should define an unambigous string

representation of the instance. (If __str__() is not defined, it

defaults to __repr__().)

* Functions and code objects can now be compared meaningfully.

* On systems supporting SunOS or SVR4 style shared libraries, dynamic

loading of modules using shared libraries is automatically configured.

Thanks to Bill Jansen and Denis Severson for contributing this change!

Built-in objects

----------------

* File objects have acquired a new method writelines() which is the

reverse of readlines(). (It does not actually write lines, just a

list of strings, but the symmetry makes the choice of name OK.)

Built-in modules

----------------

* Socket objects no longer support the avail() method. Use the select

module instead, or use this function to replace it:

def avail(f):

import select

return f in select.select([f], [], [], 0)[0]

* Initialization of stdwin is done differently. It actually modifies

sys.argv (taking out the options the X version of stdwin recognizes)

the first time it is imported.

* A new built-in module parser provides a rudimentary interface to the

python parser. Corresponding standard library modules token and symbol

defines the numeric values of tokens and non-terminal symbols.

* The posix module has aquired new functions setuid(), setgid(),

execve(), and exec() has been renamed to execv().

* The array module is extended with 8-byte object swaps, the 'i'

format character, and a reverse() method. The read() and write()

methods are renamed to fromfile() and tofile().

* The rotor module has freed of portability bugs. This introduces a

backward compatibility problem: strings encoded with the old rotor

module can't be decoded by the new version.

* For select.select(), a timeout (4th) argument of None means the same

as leaving the timeout argument out.

* Module strop (and hence standard library module string) has aquired

a new function: rindex(). Thanks to Amrit Prem!

* Module regex defines a new function symcomp() which uses an extended

regular expression syntax: parenthesized subexpressions may be labeled

using the form "\(<labelname>...\)", and the group() method can return

sub-expressions by name. Thanks to Tracy Tims for these changes!

* Multiple threads are now supported on Solaris 2. Thanks to Sjoerd

Mullender!

Standard library modules

------------------------

* The library is now split in several subdirectories: all stuff using

stdwin is in Lib/stdwin, all SGI specific (or SGI Indigo or GL) stuff

is in Lib/sgi, all Sun Sparc specific stuff is in Lib/sun4, and all

test modules are in Lib/test. The default module search path will

include all relevant subdirectories by default.

* Module os now knows about trying to import dos. It defines

functions execl(), execle(), execlp() and execvp().