Add some items
Expand the "Other Language Changes" section Rewrite various passages.
This commit is contained in:
Andrew M. Kuchling
parent
7845e7c726
commit
e995d16f71
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@ -22,10 +22,6 @@
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%
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% Optik (or whatever it gets called)
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%
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% getopt.gnu_getopt
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%
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% Docstrings now optional (with --without-doc-strings)
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%
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% New dependency argument to distutils.Extension
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%
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@ -233,7 +229,7 @@ and implemented by Jack Jansen.}
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%======================================================================
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\section{PEP 279: The \function{enumerate()} Built-in Function}
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\section{PEP 279: The \function{enumerate()} Built-in Function\label{section-enumerate}}
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A new built-in function, \function{enumerate()}, will make
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certain loops a bit clearer. \code{enumerate(thing)}, where
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@ -340,15 +336,21 @@ strings \samp{True} and \samp{False} instead of \samp{1} and \samp{0}.
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\end{seealso}
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\section{Extended Slices\label{extended-slices}}
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Ever since Python 1.4 the slice syntax has supported a third
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``stride'' argument, but the built-in sequence types have not
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supported this feature (it was initially included at the behest of the
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developers of the Numerical Python package). Starting with Python
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2.3, the built-in sequence types do support the stride.
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\section{Extended Slices\label{section-slices}}
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For example, to extract the elements of a list with even indexes:
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Ever since Python 1.4, the slicing syntax has supported an optional
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third ``step'' or ``stride'' argument. For example, these are all
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legal Python syntax: \code{L[1:10:2]}, \code{L[:-1:1]},
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\code{L[::-1]}. This was added to Python included at the request of
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the developers of Numerical Python. However, the built-in sequence
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types of lists, tuples, and strings have never supported this feature,
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and you got a \exception{TypeError} if you tried it. Michael Hudson
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contributed a patch that was applied to Python 2.3 and fixed this
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shortcoming.
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For example, you can now easily extract the elements of a list that
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have even indexes:
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\begin{verbatim}
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>>> L = range(10)
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@ -356,38 +358,137 @@ For example, to extract the elements of a list with even indexes:
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[0, 2, 4, 6, 8]
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\end{verbatim}
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To make a copy of the same list in reverse order:
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Negative values also work, so you can make a copy of the same list in
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reverse order:
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\begin{verbatim}
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>>> L[::-1]
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[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
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\end{verbatim}
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This also works for strings:
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\begin{verbatim}
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>>> s='abcd'
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>>> s[::2]
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'ac'
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>>> s[::-1]
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'dcba'
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\end{verbatim}
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%======================================================================
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\section{Other Language Changes}
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%Here are the changes that Python 2.3 makes to the core language.
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Here are all of the changes that Python 2.3 makes to the core Python
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language.
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%\begin{itemize}
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%\item The \keyword{yield} statement is now always a keyword, as
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%described in section~\ref{section-generators}.
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\begin{itemize}
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\item The \keyword{yield} statement is now always a keyword, as
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described in section~\ref{section-generators} of this document.
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%\item Two new constants, \constant{True} and \constant{False} were
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%added along with the built-in \class{bool} type, as described in
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%section~\ref{section-bool}.
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\item A new built-in function \function{enumerate()}
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was added, as described in section~\ref{section-enumerate} of this
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document.
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%\item
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%\end{itemize}
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\item Two new constants, \constant{True} and \constant{False} were
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added along with the built-in \class{bool} type, as described in
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section~\ref{section-bool} of this document.
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\item Built-in types now support the extended slicing syntax,
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as described in section~\ref{section-slices} of this document.
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%\begin{PendingDeprecationWarning}
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\item Dictionaries have a new method, \method{pop(\var{key})}, that
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returns the value corresponding to \var{key} and removes that
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key/value pair from the dictionary. \method{pop()} will raise a
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\exception{KeyError} if the requested key isn't present in the
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dictionary:
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\begin{verbatim}
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>>> d = {1:2}
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>>> d
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{1: 2}
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>>> d.pop(4)
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Traceback (most recent call last):
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File ``stdin'', line 1, in ?
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KeyError: 4
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>>> d.pop(1)
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2
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>>> d.pop(1)
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Traceback (most recent call last):
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File ``stdin'', line 1, in ?
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KeyError: pop(): dictionary is empty
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>>> d
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{}
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>>>
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\end{verbatim}
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(Patch contributed by Raymond Hettinger.)
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\item The \method{strip()}, \method{lstrip()}, and \method{rstrip()}
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string methods now have an optional argument for specifying the
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characters to strip. The default is still to remove all whitespace
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characters:
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\begin{verbatim}
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>>> ' abc '.strip()
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'abc'
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>>> '><><abc<><><>'.strip('<>')
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'abc'
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>>> '><><abc<><><>\n'.strip('<>')
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'abc<><><>\n'
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>>> u'\u4000\u4001abc\u4000'.strip(u'\u4000')
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u'\u4001abc'
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>>>
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\end{verbatim}
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\item The \method{startswith()} and \method{endswith()}
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string methods now accept negative numbers for the start and end
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parameters.
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\item Another new string method is \method{zfill()}, originally a
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function in the \module{string} module. \method{zfill()} pads a
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numeric string with zeros on the left until it's the specified width.
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Note that the \code{\%} operator is still more flexible and powerful
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than \method{zfill()}.
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\begin{verbatim}
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>>> '45'.zfill(4)
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'0045'
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>>> '12345'.zfill(4)
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'12345'
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>>> 'goofy'.zfill(6)
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'0goofy'
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\end{verbatim}
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\item
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A new warning, \exception{PendingDeprecationWarning} was added to
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provide direction on features which are in the process of being
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deprecated. The warning will not be printed by default. To see the
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pending deprecations, use
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\programopt{-Walways::PendingDeprecationWarning::} on the command line
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or use \function{warnings.filterwarnings()}.
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%\end{PendingDeprecationWarning}
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deprecated. The warning will \emph{not} be printed by default. To
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check for use of features that will be deprecated in the future,
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supply \programopt{-Walways::PendingDeprecationWarning::} on the
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command line or use \function{warnings.filterwarnings()}.
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\item One minor but far-reaching change is that the names of extension
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types defined by the modules included with Python now contain the
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module and a \samp{.} in front of the type name. For example, in
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Python 2.2, if you created a socket and printed its
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\member{__class__}, you'd get this output:
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\begin{verbatim}
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>>> s = socket.socket()
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>>> s.__class__
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<type 'socket'>
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\end{verbatim}
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In 2.3, you get this:
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\begin{verbatim}
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>>> s.__class__
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<type '_socket.socket'>
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\end{verbatim}
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\end{itemize}
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%======================================================================
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@ -457,9 +558,9 @@ support, turn on the Python interpreter's debugging code by running
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To aid extension writers, a header file \file{Misc/pymemcompat.h} is
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distributed with the source to Python 2.3 that allows Python
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extensions to use the 2.3 interfaces to memory allocation and compile
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against any version of Python since 1.5.2. (The idea is that you take
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the file from Python's source distribution and bundle it with the
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source of your extension).
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against any version of Python since 1.5.2. You would copy the file
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from Python's source distribution and bundle it with the source of
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your extension.
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\begin{seealso}
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@ -471,6 +572,7 @@ SourceForge CVS browser.}
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\end{seealso}
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%======================================================================
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\section{New and Improved Modules}
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@ -515,87 +617,6 @@ documentation for details.
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% XXX add a link to the module docs?
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(Contributed by Greg Ward.)
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\item One minor but far-reaching change is that the names of extension
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types defined by the modules included with Python now contain the
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module and a \samp{.} in front of the type name. For example, in
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Python 2.2, if you created a socket and printed its
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\member{__class__}, you'd get this output:
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\begin{verbatim}
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>>> s = socket.socket()
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>>> s.__class__
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<type 'socket'>
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\end{verbatim}
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In 2.3, you get this:
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\begin{verbatim}
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>>> s.__class__
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<type '_socket.socket'>
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\end{verbatim}
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\item The \method{strip()}, \method{lstrip()}, and \method{rstrip()}
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string methods now have an optional argument for specifying the
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characters to strip. The default is still to remove all whitespace
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characters:
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\begin{verbatim}
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>>> ' abc '.strip()
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'abc'
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>>> '><><abc<><><>'.strip('<>')
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'abc'
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>>> '><><abc<><><>\n'.strip('<>')
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'abc<><><>\n'
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>>> u'\u4000\u4001abc\u4000'.strip(u'\u4000')
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u'\u4001abc'
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>>>
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\end{verbatim}
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\item The \method{startswith()} and \method{endswith()}
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string methods now have accept negative numbers for
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start and end parameters.
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\item Another new string method is \method{zfill()}, originally a
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function in the \module{string} module. \method{zfill()} pads a
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numeric string with zeros on the left until it's the specified width.
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Note that the \code{\%} operator is still more flexible and powerful
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than \method{zfill()}.
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\begin{verbatim}
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>>> '45'.zfill(4)
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'0045'
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>>> '12345'.zfill(4)
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'12345'
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>>> 'goofy'.zfill(6)
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'0goofy'
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\end{verbatim}
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\item Dictionaries have a new method, \method{pop(\var{key})}, that
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returns the value corresponding to \var{key} and removes that
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key/value pair from the dictionary. \method{pop()} will raise a
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\exception{KeyError} if the requsted key isn't present in the
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dictionary:
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\begin{verbatim}
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>>> d = {1:2}
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>>> d
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{1: 2}
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>>> d.pop(4)
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Traceback (most recent call last):
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File ``stdin'', line 1, in ?
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KeyError: 4
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>>> d.pop(1)
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2
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>>> d.pop(1)
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Traceback (most recent call last):
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File ``stdin'', line 1, in ?
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KeyError: pop(): dictionary is empty
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>>> d
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{}
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>>>
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\end{verbatim}
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(Contributed by Raymond Hettinger.)
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\item Two new functions in the \module{math} module,
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\function{degrees(\var{rads})} and \function{radians(\var{degs})},
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convert between radians and degrees. Other functions in the
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@ -605,7 +626,25 @@ input values measured in radians. (Contributed by Raymond Hettinger.)
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\item Three new functions, \function{getpgid()}, \function{killpg()},
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and \function{mknod()}, were added to the \module{posix} module that
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underlies the \module{os} module.
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underlies the \module{os} module. (Contributed by Gustavo Niemeyer
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and Geert Jansen.)
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\item The \module{getopt} module gained a new function,
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\function{gnu_getopt()}, that supports the same arguments as the existing
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\function{getopt()} function but uses GNU-style scanning mode.
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The existing \function{getopt()} stops processing options as soon as a
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non-option argument is encountered, but in GNU-style mode processing
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continues, meaning that options and arguments can be mixed. For
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example:
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\begin{verbatim}
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>>> getopt.getopt(['-f', 'filename', 'output', '-v'], 'f:v')
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([('-f', 'filename')], ['output', '-v'])
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>>> getopt.gnu_getopt(['-f', 'filename', 'output', '-v'], 'f:v')
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([('-f', 'filename'), ('-v', '')], ['output'])
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\end{verbatim}
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(Contributed by Peter \AA{strand}.)
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\item Two new binary packagers were added to the Distutils.
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\code{bdist_pkgtool} builds \file{.pkg} files to use with Solaris
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@ -652,6 +691,13 @@ Changes to Python's build process, and to the C API, include:
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when running Python's \file{configure} script. (Contributed by Ondrej
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Palkovsky.)
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\item The interpreter can be compiled without any docstrings for
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the built-in functions and modules by supplying
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\longprogramopt{--without-doc-strings} to the \file{configure} script.
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This makes the Python executable about 10\% smaller, but will also
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mean that you can't get help for Python's built-ins. (Contributed by
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Gustavo Niemeyer.)
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\item The \cfunction{PyArg_NoArgs()} macro is now deprecated, and code
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that uses it should be changed. For Python 2.2 and later, the method
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definition table can specify the
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