mirror of https://github.com/python/cpython
Some edits; add empty sections
This commit is contained in:
parent
9aa37ab5d2
commit
437567ca7b
|
@ -16,23 +16,29 @@ This article explains the new features in Python 2.5. No release date
|
|||
for Python 2.5 has been set; it will probably be released in the
|
||||
autumn of 2006.
|
||||
|
||||
% Compare with previous release in 2 - 3 sentences here.
|
||||
% XXX Compare with previous release in 2 - 3 sentences here.
|
||||
|
||||
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 2.5.
|
||||
% add hyperlink when the documentation becomes available online.
|
||||
% XXX add hyperlink when the documentation becomes available online.
|
||||
If you want to understand the complete implementation and design
|
||||
rationale, refer to the PEP for a particular new feature.
|
||||
|
||||
|
||||
%======================================================================
|
||||
\section{PEP 308: Conditional Expressions}
|
||||
|
||||
% XXX write this
|
||||
|
||||
|
||||
%======================================================================
|
||||
\section{PEP 309: Partial Function Application}
|
||||
|
||||
The \module{functional} module is intended to contain tools for
|
||||
functional-style programming. Currently it only contains
|
||||
\class{partial}, but new functions will probably be added in future
|
||||
versions of Python.
|
||||
functional-style programming. Currently it only contains a
|
||||
\class{partial()} function, but new functions will probably be added
|
||||
in future versions of Python.
|
||||
|
||||
For programs written in a functional style, it can be useful to
|
||||
construct variants of existing functions that have some of the
|
||||
|
@ -59,6 +65,7 @@ def log (message, subsystem):
|
|||
...
|
||||
|
||||
server_log = functional.partial(log, subsystem='server')
|
||||
server_log('Unable to open socket')
|
||||
\end{verbatim}
|
||||
|
||||
Here's another example, from a program that uses PyGTk. Here a
|
||||
|
@ -91,15 +98,15 @@ Raymond Hettinger.}
|
|||
\section{PEP 314: Metadata for Python Software Packages v1.1}
|
||||
|
||||
Some simple dependency support was added to Distutils. The
|
||||
\function{setup()} function now has \code{requires},\code{provides},
|
||||
and \code{obsoletes}. When you build a source distribution using the
|
||||
\code{sdist} command, the dependency information will be recorded in
|
||||
the \file{PKG-INFO} file.
|
||||
\function{setup()} function now has \code{requires}, \code{provides},
|
||||
and \code{obsoletes} keyword parameters. When you build a source
|
||||
distribution using the \code{sdist} command, the dependency
|
||||
information will be recorded in the \file{PKG-INFO} file.
|
||||
|
||||
Another new keyword is \code{download_url}, which should be set to a
|
||||
URL for the package's source code. This means it's now possible to
|
||||
look up an entry in the package index, determine the dependencies for
|
||||
a package, and download the required packages.
|
||||
Another new keyword parameter is \code{download_url}, which should be
|
||||
set to a URL for the package's source code. This means it's now
|
||||
possible to look up an entry in the package index, determine the
|
||||
dependencies for a package, and download the required packages.
|
||||
|
||||
% XXX put example here
|
||||
|
||||
|
@ -112,16 +119,28 @@ implemented by Richard Jones and Fred Drake.}
|
|||
\end{seealso}
|
||||
|
||||
|
||||
%======================================================================
|
||||
\section{PEP 328: Absolute and Relative Imports}
|
||||
|
||||
% XXX write this
|
||||
|
||||
|
||||
%======================================================================
|
||||
\section{PEP 341: Unified try/except/finally}
|
||||
|
||||
% XXX write this
|
||||
|
||||
|
||||
%======================================================================
|
||||
\section{PEP 342: New Generator Features}
|
||||
|
||||
As introduced in Python 2.3, generators only produce output; once a
|
||||
generator's code was invoked to create an iterator, there's no way to
|
||||
pass new parameters into the function when its execution is resumed.
|
||||
Hackish solutions to this include making the generator's code look at
|
||||
a global variable and then changing the global variable's value, or
|
||||
passing in some mutable object that callers then modify. Python
|
||||
2.5 adds the ability to pass values \emph{into} a generator.
|
||||
generator's code is invoked to create an iterator, there's no way to
|
||||
pass any new information into the function when its execution is
|
||||
resumed. Hackish solutions to this include making the generator's
|
||||
code look at a global variable and then changing the global variable's
|
||||
value, or passing in some mutable object that callers then modify.
|
||||
Python 2.5 adds the ability to pass values \emph{into} a generator.
|
||||
|
||||
To refresh your memory of basic generators, here's a simple example:
|
||||
|
||||
|
@ -138,7 +157,7 @@ returns the values from 0 up to 9. On encountering the
|
|||
\keyword{yield} statement, the iterator returns the provided value and
|
||||
suspends the function's execution, preserving the local variables.
|
||||
Execution resumes on the following call to the iterator's
|
||||
\method{next()} method, picking up after the \keyword{yield}.
|
||||
\method{next()} method, picking up after the \keyword{yield} statement.
|
||||
|
||||
In Python 2.3, \keyword{yield} was a statement; it didn't return any
|
||||
value. In 2.5, \keyword{yield} is now an expression, returning a
|
||||
|
@ -152,17 +171,17 @@ I recommend that you always put parentheses around a \keyword{yield}
|
|||
expression when you're doing something with the returned value, as in
|
||||
the above example. The parentheses aren't always necessary, but it's
|
||||
easier to always add them instead of having to remember when they're
|
||||
needed. The exact rules are that a \keyword{yield}-expression must
|
||||
needed.\footnote{The exact rules are that a \keyword{yield}-expression must
|
||||
always be parenthesized except when it occurs at the top-level
|
||||
expression on the right-hand side of an assignment, meaning
|
||||
you can to write \code{val = yield i} but \code{val = (yield i) + 12}.
|
||||
% XXX ending of last para makes no sense
|
||||
expression on the right-hand side of an assignment, meaning you can
|
||||
write \code{val = yield i} but have to use parentheses when there's an
|
||||
operation, as in \code{val = (yield i) + 12}.}
|
||||
|
||||
Values are sent into a generator by calling its
|
||||
\method{send(\var{value})} method. The generator's code is then
|
||||
resumed and the \keyword{yield} expression produces \var{value}.
|
||||
If the regular \method{next()} method is called, the \keyword{yield}
|
||||
returns \constant{None}.
|
||||
resumed and the \keyword{yield} expression returns the specified
|
||||
\var{value}. If the regular \method{next()} method is called, the
|
||||
\keyword{yield} returns \constant{None}.
|
||||
|
||||
Here's the previous example, modified to allow changing the value of
|
||||
the internal counter.
|
||||
|
@ -198,12 +217,13 @@ Traceback (most recent call last):
|
|||
StopIteration
|
||||
\end{verbatim}
|
||||
|
||||
Because \keyword{yield} will often be returning \constant{None},
|
||||
you shouldn't just use its value in expressions unless you're sure
|
||||
that only the \method{send()} method will be used.
|
||||
Because \keyword{yield} will often be returning \constant{None}, you
|
||||
should always check for this case. Don't just use its value in
|
||||
expressions unless you're sure that the \method{send()} method
|
||||
will be the only method used resume your generator function.
|
||||
|
||||
There are two other new methods on generators in addition to
|
||||
\method{send()}:
|
||||
In addition to \method{send()}, there are two other new methods on
|
||||
generators:
|
||||
|
||||
\begin{itemize}
|
||||
|
||||
|
@ -229,13 +249,14 @@ There are two other new methods on generators in addition to
|
|||
|
||||
The cumulative effect of these changes is to turn generators from
|
||||
one-way producers of information into both producers and consumers.
|
||||
|
||||
Generators also become \emph{coroutines}, a more generalized form of
|
||||
subroutines; subroutines are entered at one point and exited at
|
||||
subroutines. Subroutines are entered at one point and exited at
|
||||
another point (the top of the function, and a \keyword{return
|
||||
statement}), but coroutines can be entered, exited, and resumed at
|
||||
many different points (the \keyword{yield} statements).science term
|
||||
many different points (the \keyword{yield} statements).
|
||||
|
||||
|
||||
|
||||
\begin{seealso}
|
||||
|
||||
\seepep{342}{Coroutines via Enhanced Generators}{PEP written by
|
||||
|
@ -253,6 +274,18 @@ Sugalski.}
|
|||
\end{seealso}
|
||||
|
||||
|
||||
%======================================================================
|
||||
\section{PEP 343: The 'with' statement}
|
||||
|
||||
% XXX write this
|
||||
|
||||
|
||||
%======================================================================
|
||||
\section{PEP 357: The '__index__' method}
|
||||
|
||||
% XXX write this
|
||||
|
||||
|
||||
%======================================================================
|
||||
\section{Other Language Changes}
|
||||
|
||||
|
|
Loading…
Reference in New Issue