random version of the CVS tree around May 26 2002. Please send any

\label{section-generators}

The three major operating systems used today are Microsoft Windows,

Apple's Macintosh OS, and the various Unix derivatives. A minor

irritation is that these three platforms all use different characters

to mark the ends of lines in text files. Unix uses character 10, the

ASCII linefeed, MacOS uses character 13, the ASCII carriage return,

and Windows uses a two-character sequence of carriage return plus a

newline.

Python's file objects can now support end of line conventions other

than the one followed by the platform on which Python is running.

Opening a file with the mode \samp{U} or \samp{rU} will open a file

for reading in universal newline mode. All three line ending

conventions will be translated to a \samp{\e n} in the strings

returned by the various file methods such as \method{read()} and

\method{readline()}.

Universal newline support is also used when importing modules and when

executing a file with the \function{execfile()} function. This means

that Python modules can be shared between all three operating systems

without needing to convert the line-endings.

This feature can be disabled at compile-time by specifying the

\longprogramopt{without-universal-newlines} when running Python's

configure script.

\label{section-bool}

A Boolean type was added to Python 2.3. Two new constants were added

to the \module{__builtin__} module, \constant{True} and

\constant{False}. The type object for this new type is named

\class{bool}; the constructor for it takes any Python value and

converts it to \constant{True} or \constant{False}.

\begin{verbatim}

\end{verbatim}

Most of the standard library modules and built-in functions have been

changed to return Booleans.

\begin{verbatim}

\end{verbatim}

Python's Booleans were added with the primary goal of making code

clearer. For example, if you're reading a function and encounter the

statement \code{return 1}, you might wonder whether the \samp{1}

represents a truth value, or whether it's an index, or whether it's a

coefficient that multiplies some other quantity. If the statement is

\code{return True}, however, the meaning of the return value is quite

clearly a truth value.

Python's Booleans were not added for the sake of strict type-checking.

A very strict language such as Pascal

would also prevent you performing arithmetic with Booleans, and would

require that the expression in an \keyword{if} statement always

evaluate to a Boolean. Python is not this strict, and it never will

be. (\pep{285} explicitly says this.) So you can still use any

expression in an \keyword{if}, even ones that evaluate to a list or

tuple or some random object, and the Boolean type is a subclass of the

\class{int} class, so arithmetic using a Boolean still works.

\begin{verbatim}

\end{verbatim}

To sum up \constant{True} and \constant{False} in a sentence: they're

alternative ways to spell the integer values 1 and 0, with the single

difference that \function{str()} and \function{repr()} return the

strings \samp{True} and \samp{False} instead of \samp{1} and \samp{0}.

As usual, Python's standard modules had a number of enhancements and

bug fixes. Here's a partial list; consult the \file{Misc/NEWS} file

in the source tree, or the CVS logs, for a more complete list.

\begin{itemize}

\item One minor but far-reaching change is that the names of extension

types defined by the modules included with Python now contain the

module and a \samp{.} in front of the type name. For example, in

Python 2.2, if you created a socket and printed its

\member{__class__}, you'd get this output:

\begin{verbatim}

\end{verbatim}

In 2.3, you get this:

\begin{verbatim}

\end{verbatim}

\item The \method{strip()}, \method{lstrip()}, and \method{rstrip()}

string methods now have an optional argument for specifying the

characters to strip. The default is still to remove all whitespace

characters:

\begin{verbatim}

\end{verbatim}

\item Another new string method is \method{zfill()}, originally a

function in the \module{string} module. \method{zfill()} pads a

numeric string with zeros on the left until it's the specified width.

Note that the \code{\%} operator is still more flexible and powerful

than \method{zfill()}.

\begin{verbatim}

\end{verbatim}

\item Dictionaries have a new method, method{pop(\var{key})}, that

returns the value corresponding to \var{key} and removes that

key/value pair from the dictionary. \method{pop()} will raise a

\exception{KeyError} if the requsted key isn't present in the

dictionary:

\begin{verbatim}

\end{verbatim}

\item Two new functions, \function{killpg()} and \function{mknod()},

were added to the \module{posix} module that underlies the \module{os}

module.

\item (XXX write this) arraymodule.c: - add Py_UNICODE arrays

- support +=, *=

\item The \module{grp} module now returns enhanced tuples:

\begin{verbatim}

\end{verbatim}

\item The \module{readline} module also gained a number of new

functions: \function{get_history_item()},

\function{get_current_history_length()}, and \function{redisplay()}.

\end{itemize}

Here are the changes that Python 2.3 makes to the core language.

\begin{itemize}

\item The \keyword{yield} statement is now always a keyword, as

described in section~\ref{section-generators}.

\item Two new constants, \constant{True} and \constant{False} were

added along with the built-in \class{bool} type, as described in

section~\ref{section-bool}.

\item The \class{file} type can now be subtyped. (XXX did this not work

before? Thought I used it in an example in the 2.2 What's New document...)

\item File objects also manage their internal string buffer

differently by increasing it exponentially when needed.

This results in the benchmark tests in \file{Lib/test/test_bufio.py}

speeding up from 57 seconds to 1.7 seconds, according to one

measurement.

\end{itemize}

XXX write this

\section{Build and C API Changes}

XXX write this

\begin{itemize}

\item Patch \#527027: Allow building python as shared library with

\item The source code for the Expat XML parser is now included with

the Python source, so the \module{pyexpat} module is no longer

dependent on having a system library containing Expat.

\end{itemize}

\subsection{Port-Specific Changes}

XXX write this