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Diffstat (limited to 'Doc/whatsnew/whatsnew25.tex')
| -rw-r--r-- | Doc/whatsnew/whatsnew25.tex | 48 |
1 files changed, 26 insertions, 22 deletions
diff --git a/Doc/whatsnew/whatsnew25.tex b/Doc/whatsnew/whatsnew25.tex index bf939c0..fb68acc 100644 --- a/Doc/whatsnew/whatsnew25.tex +++ b/Doc/whatsnew/whatsnew25.tex @@ -409,7 +409,7 @@ is always executed, or one or more \keyword{except} blocks to catch specific exceptions. You couldn't combine both \keyword{except} blocks and a \keyword{finally} block, because generating the right bytecode for the combined version was complicated and it wasn't clear what the -semantics of the combined should be. +semantics of the combined statement should be. Guido van~Rossum spent some time working with Java, which does support the equivalent of combining \keyword{except} blocks and a @@ -540,10 +540,10 @@ Traceback (most recent call last): StopIteration \end{verbatim} -Because \keyword{yield} will often be returning \constant{None}, you +\keyword{yield} will usually return \constant{None}, so 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. +will be the only method used to resume your generator function. In addition to \method{send()}, there are two other new methods on generators: @@ -683,22 +683,22 @@ with lock: The lock is acquired before the block is executed and always released once the block is complete. -The \module{decimal} module's contexts, which encapsulate the desired -precision and rounding characteristics for computations, provide a -\method{context_manager()} method for getting a context manager: +The new \function{localcontext()} function in the \module{decimal} module +makes it easy to save and restore the current decimal context, which +encapsulates the desired precision and rounding characteristics for +computations: \begin{verbatim} -import decimal +from decimal import Decimal, Context, localcontext # Displays with default precision of 28 digits -v1 = decimal.Decimal('578') -print v1.sqrt() +v = Decimal('578') +print v.sqrt() -ctx = decimal.Context(prec=16) -with ctx.context_manager(): +with localcontext(Context(prec=16)): # All code in this block uses a precision of 16 digits. # The original context is restored on exiting the block. - print v1.sqrt() + print v.sqrt() \end{verbatim} \subsection{Writing Context Managers\label{context-managers}} @@ -1115,12 +1115,14 @@ Some examples: \begin{verbatim} >>> ('http://www.python.org').partition('://') ('http', '://', 'www.python.org') ->>> (u'Subject: a quick question').partition(':') -(u'Subject', u':', u' a quick question') >>> ('file:/usr/share/doc/index.html').partition('://') ('file:/usr/share/doc/index.html', '', '') +>>> (u'Subject: a quick question').partition(':') +(u'Subject', u':', u' a quick question') >>> 'www.python.org'.rpartition('.') ('www.python', '.', 'org') +>>> 'www.python.org'.rpartition(':') +('', '', 'www.python.org') \end{verbatim} (Implemented by Fredrik Lundh following a suggestion by Raymond Hettinger.) @@ -2114,14 +2116,16 @@ The pysqlite module (\url{http://www.pysqlite.org}), a wrapper for the SQLite embedded database, has been added to the standard library under the package name \module{sqlite3}. -SQLite is a C library that provides a SQL-language database that -stores data in disk files without requiring a separate server process. +SQLite is a C library that provides a lightweight disk-based database +that doesn't require a separate server process and allows accessing +the database using a nonstandard variant of the SQL query language. +Some applications can use SQLite for internal data storage. It's also +possible to prototype an application using SQLite and then port the +code to a larger database such as PostgreSQL or Oracle. + pysqlite was written by Gerhard H\"aring and provides a SQL interface compliant with the DB-API 2.0 specification described by -\pep{249}. This means that it should be possible to write the first -version of your applications using SQLite for data storage. If -switching to a larger database such as PostgreSQL or Oracle is -later necessary, the switch should be relatively easy. +\pep{249}. If you're compiling the Python source yourself, note that the source tree doesn't include the SQLite code, only the wrapper module. @@ -2148,8 +2152,8 @@ c = conn.cursor() # Create table c.execute('''create table stocks -(date timestamp, trans varchar, symbol varchar, - qty decimal, price decimal)''') +(date text, trans text, symbol text, + qty real, price real)''') # Insert a row of data c.execute("""insert into stocks |