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Diffstat (limited to 'Doc/whatsnew/3.2.rst')
| -rw-r--r-- | Doc/whatsnew/3.2.rst | 160 |
1 files changed, 80 insertions, 80 deletions
diff --git a/Doc/whatsnew/3.2.rst b/Doc/whatsnew/3.2.rst index 7ec33db..0d28baa 100644 --- a/Doc/whatsnew/3.2.rst +++ b/Doc/whatsnew/3.2.rst @@ -208,10 +208,10 @@ dictionary:: If that dictionary is stored in a file called :file:`conf.json`, it can be loaded and called with code like this:: - >>> import logging.config - >>> logging.config.dictConfig(json.load(open('conf.json', 'rb'))) - >>> logging.info("Transaction completed normally") - >>> logging.critical("Abnormal termination") + import logging.config + logging.config.dictConfig(json.load(open('conf.json', 'rb'))) + logging.info("Transaction completed normally") + logging.critical("Abnormal termination") .. seealso:: @@ -482,24 +482,24 @@ Some smaller changes made to the core Python language are: * Previously it was illegal to delete a name from the local namespace if it occurs as a free variable in a nested block:: - >>> def outer(x): - ... def inner(): - ... return x - ... inner() - ... del x + def outer(x): + def inner(): + return x + inner() + del x This is now allowed. Remember that the target of an :keyword:`except` clause is cleared, so this code which used to work with Python 2.6, raised a :exc:`SyntaxError` with Python 3.1 and now works again:: - >>> def f(): - ... def print_error(): - ... print(e) - ... try: - ... something - ... except Exception as e: - ... print_error() - ... # implicit "del e" here + def f(): + def print_error(): + print(e) + try: + something + except Exception as e: + print_error() + # implicit "del e" here (See :issue:`4617`.) @@ -598,7 +598,7 @@ Another significant win is the addition of substantially better support for *SSL* connections and security certificates. In addition, more classes now implement a :term:`context manager` to support -convenient and reliable resource clean-up using the :keyword:`with`-statement. +convenient and reliable resource clean-up using the :keyword:`with` statement. email ----- @@ -682,16 +682,16 @@ functools resource whenever the results are expected to be the same. For example, adding a caching decorator to a database query function can save - database accesses for popular searches:: + database accesses for popular searches: - @functools.lru_cache(maxsize=300) - def get_phone_number(name): - c = conn.cursor() - c.execute('SELECT phonenumber FROM phonelist WHERE name=?', (name,)) - return c.fetchone()[0] + >>> @functools.lru_cache(maxsize=300) + >>> def get_phone_number(name): + c = conn.cursor() + c.execute('SELECT phonenumber FROM phonelist WHERE name=?', (name,)) + return c.fetchone()[0] >>> for name in user_requests: - ... get_phone_number(name) # cached lookup + get_phone_number(name) # cached lookup To help with choosing an effective cache size, the wrapped function is instrumented for tracking cache statistics: @@ -928,7 +928,7 @@ both roles. The basic idea is that both context managers and function decorators can be used for pre-action and post-action wrappers. Context managers wrap a group of -statements using the :keyword:`with`-statement, and function decorators wrap a +statements using the :keyword:`with` statement, and function decorators wrap a group of statements enclosed in a function. So, occasionally there is a need to write a pre-action or post-action wrapper that can be used in either role. @@ -936,32 +936,32 @@ For example, it is sometimes useful to wrap functions or groups of statements with a logger that can track the time of entry and time of exit. Rather than writing both a function decorator and a context manager for the task, the :func:`~contextlib.contextmanager` provides both capabilities in a single -definition: +definition:: ->>> import logging ->>> logging.basicConfig(level=logging.INFO) ->>> @contextmanager -... def track_entry_and_exit(name): -... logging.info('Entering: {}'.format(name)) -... yield -... logging.info('Exiting: {}'.format(name)) + import logging + logging.basicConfig(level=logging.INFO) + @contextmanager + def track_entry_and_exit(name): + logging.info('Entering: {}'.format(name)) + yield + logging.info('Exiting: {}'.format(name)) -Formerly, this would have only been usable as a context manager: +Formerly, this would have only been usable as a context manager:: ->>> with track_entry_and_exit('widget loader'): -... print('Some time consuming activity goes here') -... load_widget() + with track_entry_and_exit('widget loader'): + print('Some time consuming activity goes here') + load_widget() -Now, it can be used as a decorator as well: +Now, it can be used as a decorator as well:: ->>> @track_entry_and_exit('widget loader') -... def activity(): -... print('Some time consuming activity goes here') -... load_widget() + @track_entry_and_exit('widget loader') + def activity(): + print('Some time consuming activity goes here') + load_widget() Trying to fulfill two roles at once places some limitations on the technique. Context managers normally have the flexibility to return an argument usable by -the :keyword:`with`-statement, but there is no parallel for function decorators. +the :keyword:`with` statement, but there is no parallel for function decorators. In the above example, there is not a clean way for the *track_entry_and_exit* context manager to return a logging instance for use in the body of enclosed @@ -976,8 +976,8 @@ Mark Dickinson crafted an elegant and efficient scheme for assuring that different numeric datatypes will have the same hash value whenever their actual values are equal (:issue:`8188`):: - >>> assert hash(Fraction(3, 2)) == hash(1.5) == \ - hash(Decimal("1.5")) == hash(complex(1.5, 0)) + assert hash(Fraction(3, 2)) == hash(1.5) == \ + hash(Decimal("1.5")) == hash(complex(1.5, 0)) An early decision to limit the inter-operability of various numeric types has been relaxed. It is still unsupported (and ill-advised) to to have implicit @@ -1235,10 +1235,10 @@ names. * The :mod:`unittest` module has two new methods, :meth:`~unittest.TestCase.assertWarns` and :meth:`~unittest.TestCase.assertWarnsRegex` to verify that a given warning type - is triggered by the code under test: + is triggered by the code under test:: - >>> with self.assertWarns(DeprecationWarning): - ... legacy_function('XYZ') + with self.assertWarns(DeprecationWarning): + legacy_function('XYZ') (Contributed by Antoine Pitrou, :issue:`9754`.) @@ -1331,10 +1331,10 @@ tempfile The :mod:`tempfile` module has a new context manager, :class:`~tempfile.TemporaryDirectory` which provides easy deterministic -cleanup of temporary directories: +cleanup of temporary directories:: ->>> with tempfile.TemporaryDirectory() as tmpdirname: -... print('created temporary dir:', tmpdirname) + with tempfile.TemporaryDirectory() as tmpdirname: + print('created temporary dir:', tmpdirname) (Contributed by Neil Schemenauer and Nick Coghlan; :issue:`5178`.) @@ -1456,13 +1456,13 @@ Config parsers gained a new API based on the mapping protocol:: >>> parser = ConfigParser() >>> parser.read_string(""" - ... [DEFAULT] - ... monty = python - ... - ... [phrases] - ... the = who - ... full = metal jacket - ... """) + [DEFAULT] + monty = python + + [phrases] + the = who + full = metal jacket + """) >>> parser['phrases']['full'] 'metal jacket' >>> section = parser['phrases'] @@ -1485,24 +1485,24 @@ support for pluggable interpolation, an additional interpolation handler >>> parser = ConfigParser(interpolation=ExtendedInterpolation()) >>> parser.read_dict({'buildout': {'directory': '/home/ambv/zope9'}, - ... 'custom': {'prefix': '/usr/local'}}) + 'custom': {'prefix': '/usr/local'}}) >>> parser.read_string(""" - ... [buildout] - ... parts = - ... zope9 - ... instance - ... find-links = - ... ${buildout:directory}/downloads/dist - ... - ... [zope9] - ... recipe = plone.recipe.zope9install - ... location = /opt/zope - ... - ... [instance] - ... recipe = plone.recipe.zope9instance - ... zope9-location = ${zope9:location} - ... zope-conf = ${custom:prefix}/etc/zope.conf - ... """) + [buildout] + parts = + zope9 + instance + find-links = + ${buildout:directory}/downloads/dist + + [zope9] + recipe = plone.recipe.zope9install + location = /opt/zope + + [instance] + recipe = plone.recipe.zope9instance + zope9-location = ${zope9:location} + zope-conf = ${custom:prefix}/etc/zope.conf + """) >>> parser['buildout']['find-links'] '\n/home/ambv/zope9/downloads/dist' >>> parser['instance']['zope-conf'] @@ -1876,10 +1876,10 @@ require changes to your code: and it does a better job finalizing multiple context managers when one of them raises an exception:: - >>> with open('mylog.txt') as infile, open('a.out', 'w') as outfile: - ... for line in infile: - ... if '<critical>' in line: - ... outfile.write(line) + with open('mylog.txt') as infile, open('a.out', 'w') as outfile: + for line in infile: + if '<critical>' in line: + outfile.write(line) (Contributed by Georg Brandl and Mattias Brändström; `appspot issue 53094 <http://codereview.appspot.com/53094>`_.) |