path: root/Misc/NEWS

=======================================
==> 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 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 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!

* 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().

* New module dospath (should be attacked by a DOS hacker though).

* All modules defining classes now define __init__() constructors
instead of init() methods.  THIS IS AN INCOMPATIBLE CHANGE!

* Some minor changes and bugfixes module ftplib (mostly Steve
Majewski's suggestions); the debug() method is renamed to
set_debuglevel().

* Some new test modules (not run automatically by testall though):
test_audioop, test_md5, test_rgbimg, test_select.

* Module string now defines rindex() and rfind() in analogy of index()
and find().  It also defines atof() and atol() (and corresponding
exceptions) in analogy to atoi().

* Added help() functions to modules profile and pdb.

* The wdb debugger (now in Lib/stdwin) now shows class or instance
variables on a double click.  Thanks to Sjoerd Mullender!

* The (undocumented) module lambda has gone -- you couldn't import it
any more, and it was basically more a demo than a library module...


Multimedia extensions
---------------------

* The optional built-in modules audioop and imageop are now standard
parts of the interpreter.  Thanks to Sjoerd Mullender and Jack Jansen
for contributing this code!

* There's a new operation in audioop: minmax().

* There's a new built-in module called rgbimg which supports portable
efficient reading of SGI RCG image files.  Thanks also to Paul
Haeberli for the original code!  (Who will contribute a GIF reader?)

* The module aifc is gone -- you should now always use aifc, which has
received a facelift.

* There's a new module sunau., for reading Sun (and NeXT) audio files.

* There's a new module audiodev which provides a uniform interface to
(SGI Indigo and Sun Sparc) audio hardware.

* There's a new module sndhdr which recognizes various sound files by
looking in their header and checking for various magic words.


Optimizations
-------------

* Most optimizations below can be configured by compile-time flags.
Thanks to Sjoerd Mullender for submitting these optimizations!

* Small integers (default -1..99) are shared -- i.e. if two different
functions compute the same value it is possible (but not
guaranteed!!!) that they return the same *object*.  Python programs
can detect this but should *never* rely on it.

* Empty tuples (which all compare equal) are shared in the same
manner.

* Tuples of size up to 20 (default) are put in separate free lists
when deallocated.

* There is a compile-time option to cache a string's hash function,
but this appeared to have a negligeable effect, and as it costs 4
bytes per string it is disabled by default.


Embedding Python
----------------

* The initialization interface has been simplified somewhat.  You now
only call "initall()" to initialize the interpreter.

* The previously announced renaming of externally visible identifiers
has not been carried out.  It will happen in a later release.  Sorry.


Miscellaneous bugs that have been fixed
---------------------------------------

* All known portability bugs.

* Version 0.9.9 dumped core in <listobject>.sort() which has been
fixed.  Thanks to Jaap Vermeulen for fixing this and posting the fix
on the mailing list while I was away!

* Core dump on a format string ending in '%', e.g. in the expression
'%' % None.

* The array module yielded a bogus result for concatenation (a+b would
yield a+a).

* Some serious memory leaks in strop.split() and strop.splitfields().

* Several problems with the nis module.

* Subtle problem when copying a class method from another class
through assignment (the method could not be called).


Remaining bugs
--------------

* One problem with 64-bit machines remains -- since .pyc files are
portable and use only 4 bytes to represent an integer object, 64-bit
integer literals are silently truncated when written into a .pyc file.
Work-around: use eval('123456789101112').

* The freeze script doesn't work any more.  A new and more portable
one can probably be cooked up using tricks from Extensions/mkext.py.

* The dos support hasn't been tested yet.  (Really Soon Now we should
have a PC with a working C compiler!)


--Guido van Rossum, CWI, Amsterdam <Guido.van.Rossum@cwi.nl>
URL:  <http://www.cwi.nl/cwi/people/Guido.van.Rossum.html>