[Python-checkins] r45562 - python/trunk/Doc/whatsnew/whatsnew25.tex (original) (raw)

andrew.kuchling python-checkins at python.org
Wed Apr 19 14:55:39 CEST 2006

Author: andrew.kuchling Date: Wed Apr 19 14:55:39 2006 New Revision: 45562

Modified: python/trunk/Doc/whatsnew/whatsnew25.tex Log: Write datetime.strptime() item; show use of @contextmanager in defining context methods; minor edits; add two names

Modified: python/trunk/Doc/whatsnew/whatsnew25.tex

--- python/trunk/Doc/whatsnew/whatsnew25.tex (original) +++ python/trunk/Doc/whatsnew/whatsnew25.tex Wed Apr 19 14:55:39 2006 @@ -145,7 +145,7 @@ \begin{seealso} \seepep{308}{Conditional Expressions}{PEP written by -Guido van Rossum and Raymond D. Hettinger; implemented by Thomas +Guido vanRossum and Raymond D. Hettinger; implemented by Thomas Wouters.} \end{seealso} @@ -549,7 +549,7 @@ therefore been removed. This seems like a minor bit of language trivia, but using generators and \code{try...finally} is actually necessary in order to implement the \keyword{with} statement -described by PEP 343. We'll look at this new statement in the following +described by PEP 343. I'll look at this new statement in the following section. Another even more esoteric effect of this change: previously, the @@ -560,7 +560,7 @@ \begin{seealso} \seepep{342}{Coroutines via Enhanced Generators}{PEP written by -Guido van Rossum and Phillip J. Eby; +Guido vanRossum and Phillip J. Eby; implemented by Phillip J. Eby. Includes examples of some fancier uses of generators as coroutines.} @@ -581,10 +581,10 @@ uses \code{try...finally} blocks to ensure that clean-up code is executed. -First, I'll discuss the statement as it will commonly be used, and -then a subsection will examine the implementation details and how to -write objects (called context managers'') that can be used with this -statement. +In this section, I'll discuss the statement as it will commonly be +used. In the next section, I'll examine the implementation details +and show how to write objects called context managers'' and +contexts'' for use with this statement. The \keyword{with} statement is a new control-flow structure whose basic structure is: @@ -830,10 +830,29 @@ ... \end{verbatim} -There's a \function{nested(\var{mgr1}, \var{mgr2}, ...)} manager that -combines a number of context managers so you don't need to write -nested \keyword{with} statements. This example -both uses a database transaction and also acquires a thread lock: +You can also use this decorator to write the \method{__context__()} method +for a class without creating a new class for the context: + +\begin{verbatim} +class DatabaseConnection: + + @contextmanager + def __context__ (self): + cursor = self.cursor() + try: + yield cursor + except: + self.rollback() + raise + else: + self.commit() +\end{verbatim} + + +There's a \function{nested(\var{mgr1}, \var{mgr2}, ...)} manager that +combines a number of context managers so you don't need to write +nested \keyword{with} statements. This example statement does two +things, starting a database transaction and acquiring a thread lock: \begin{verbatim} lock = threading.Lock() @@ -853,8 +872,8 @@ \begin{seealso} -\seepep{343}{The with'' statement}{PEP written by Guido van Rossum -and Nick Coghlan; implemented by Mike Bland, Guido van Rossum, and +\seepep{343}{The ``with'' statement}{PEP written by Guido vanRossum +and Nick Coghlan; implemented by Mike Bland, Guido vanRossum, and Neal Norwitz. The PEP shows the code generated for a \keyword{with} statement, which can be helpful in learning how context managers work.} @@ -926,7 +945,7 @@ \begin{seealso} \seepep{352}{Required Superclass for Exceptions}{PEP written by -Brett Cannon and Guido van Rossum; implemented by Brett Cannon.} +Brett Cannon and Guido van~Rossum; implemented by Brett Cannon.} \end{seealso} @@ -1174,9 +1193,6 @@ % the cPickle module no longer accepts the deprecated None option in the % args tuple returned by reduce(). -% XXX datetime.datetime() now has a strptime class method which can be used to -% create datetime object using a string and format.

% XXX fileinput: opening hook used to control how files are opened. % .input() now has a mode parameter % now has a fileno() function @@ -1250,6 +1266,19 @@ \member{line_num} is not the same as the number of records read. (Contributed by Skip Montanaro and Andrew McNamara.)

+\item The \class{datetime} class in the \module{datetime} +module now has a \method{strptime(\var{string}, \var{format})} +method for parsing date strings, contributed by Josh Spoerri. +It uses the same format characters as \function{time.strptime()} and +\function{time.strftime()}: + +\begin{verbatim} +from datetime import datetime + +ts = datetime.strptime('10:13:15 2006-03-07',

+\end{verbatim} + \item In the \module{gc} module, the new \function{get_count()} function returns a 3-tuple containing the current collection counts for the three GC generations. This is accounting information for the garbage @@ -1943,6 +1972,7 @@

The author would like to thank the following people for offering suggestions, corrections and assistance with various drafts of this -article: Martin vonL"owis, Mike Rovner, Thomas Wouters. +article: Phillip J. Eby, Kent Johnson, Martin vonL"owis, Mike +Rovner, Thomas Wouters.

\end{document}

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