Kaydet (Commit) 35f2b05d authored tarafından Andrew M. Kuchling's avatar Andrew M. Kuchling

Add various items

üst 852fe068
......@@ -20,11 +20,13 @@ as-yet-undetermined ways.
This article doesn't attempt to provide a complete specification of
the new features, but instead provides a convenient overview. For
full details, you should refer to the documentation for Python 2.4.
% add hyperlink when the documentation becomes available online.
full details, you should refer to the documentation for Python 2.4,
such as the \citetitle[../lib/lib.html]{Python Library Reference} and
the \citetitle[../ref/ref.html]{Python Reference Manual}.
If you want to understand the complete implementation and design
rationale, refer to the PEP for a particular new feature.
%======================================================================
\section{PEP 218: Built-In Set Objects}
......@@ -67,11 +69,18 @@ Since it is immutable and hashable, it may be used as a dictionary key or
as a member of another set. Accordingly, it does not have methods
like \method{add()} and \method{remove()} which could alter its contents.
% XXX what happens to the sets module?
\begin{seealso}
\seepep{218}{Adding a Built-In Set Object Type}{Originally proposed by
Greg Wilson and ultimately implemented by Raymond Hettinger.}
\end{seealso}
%======================================================================
\section{PEP 237: Unifying Long Integers and Integers}
XXX write this.
%======================================================================
\section{PEP 322: Reverse Iteration}
......@@ -122,6 +131,16 @@ language.
\method{center()} now take an optional argument for specifying a
fill character other than a space.
\item Strings also gained an \method{rsplit()} method that
works like the \method{split()} method but splits from the end of the string.
\begin{verbatim}
>>> 'a b c'.split(None, 1)
['a', 'b c']
>>> 'a b c'.rsplit(None, 1)
['a b', 'c']
\end{verbatim}
\item The \method{sort()} method of lists gained three keyword
arguments, \var{cmp}, \var{key}, and \var{reverse}. These arguments
make some common usages of \method{sort()} simpler. All are optional.
......@@ -177,7 +196,7 @@ they were input. For example, you can sort a list of people by name,
and then sort the list by age, resulting in a list sorted by age where
people with the same age are in name-sorted order.
\item There is a new builtin function \function{sorted(iterable)} that works
\item There is a new built-in function \function{sorted(iterable)} that works
like the in-place \method{list.sort()} method but has been made suitable
for use in expressions. The differences are:
\begin{itemize}
......@@ -209,7 +228,6 @@ yellow 5
\end{verbatim}
\item The \function{zip()} built-in function and \function{itertools.izip()}
now return an empty list instead of raising a \exception{TypeError}
exception if called with no arguments. This makes the functions more
......@@ -312,10 +330,48 @@ counting, or identifying duplicate elements:
['a', 'b', 'r']
\end{verbatim}
\item \module{itertools} also gained a function named \function{tee(\var{iterator}, \var{N})} that returns \var{N} independent iterators
that replicate \var{iterator}. If \var{N} is omitted, the default is
2.
\begin{verbatim}
>>> L = [1,2,3]
>>> i1, i2 = itertools.tee(L)
>>> i1,i2
(<itertools.tee object at 0x402c2080>, <itertools.tee object at 0x402c2090>)
>>> list(i1)
[1, 2, 3]
>>> list(i2)
[1, 2, 3]
>\end{verbatim}
Note that \function{tee()} has to keep copies of the values returned
by the iterator; in the worst case it may need to keep all of them.
This should therefore be used carefully if \var{iterator}
returns a very large stream of results.
\item A new \function{getsid()} function was added to the
\module{posix} module that underlies the \module{os} module.
(Contributed by J. Raynor.)
\item The \module{operator} module gained two new functions,
\function{attrgetter(\var{attr})} and \function{itemgetter(\var{index})}.
Both functions return callables that take a single argument and return
the corresponding attribute or item; these callables are handy for use
with \function{map()} or \function{list.sort()}. For example, here's a simple
us
\begin{verbatim}
>>> L = [('c', 2), ('d', 1), ('a', '4'), ('b', 3)]
>>> map(operator.itemgetter(0), L)
['c', 'd', 'a', 'b']
>>> map(operator.itemgetter(1), L)
[2, 1, '4', 3]
>>> L.sort(key=operator.itemgetter(1)) # Sort list by second item in tuples
>>> L
[('d', 1), ('c', 2), ('b', 3), ('a', '4')]
\end{verbatim}
\item The \module{random} module has a new method called \method{getrandbits(N)}
which returns an N-bit long integer. This method supports the existing
\method{randrange()} method, making it possible to efficiently generate
......
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