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Edit four more sections
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Andrew M. Kuchling
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@ -498,12 +498,15 @@ Python's :option:`-m` switch allows running a module as a script.
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When you ran a module that was located inside a package, relative
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imports didn't work correctly.
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The fix in Python 2.6 adds a :attr:`__package__` attribute to modules.
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When present, relative imports will be relative to the value of this
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attribute instead of the :attr:`__name__` attribute. PEP 302-style
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importers can then set :attr:`__package__`. The :mod:`runpy` module
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that implements the :option:`-m` switch now does this, so relative imports
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can now be used in scripts running from inside a package.
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The fix for Python 2.6 adds a :attr:`__package__` attribute to
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modules. When this attribute is present, relative imports will be
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relative to the value of this attribute instead of the
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:attr:`__name__` attribute.
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PEP 302-style importers can then set :attr:`__package__` as necessary.
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The :mod:`runpy` module that implements the :option:`-m` switch now
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does this, so relative imports will now work correctly in scripts
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running from inside a package.
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.. ======================================================================
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@ -512,10 +515,10 @@ can now be used in scripts running from inside a package.
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PEP 370: Per-user ``site-packages`` Directory
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=====================================================
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When you run Python, the module search path ``sys.modules`` usually
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When you run Python, the module search path ``sys.path`` usually
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includes a directory whose path ends in ``"site-packages"``. This
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directory is intended to hold locally-installed packages available to
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all users on a machine or using a particular site installation.
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all users using a machine or a particular site installation.
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Python 2.6 introduces a convention for user-specific site directories.
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The directory varies depending on the platform:
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@ -568,8 +571,8 @@ the :meth:`is_alive` method to check whether the subprocess is still running
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and the :meth:`join` method to wait for the process to exit.
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Here's a simple example where the subprocess will calculate a
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factorial. The function doing the calculation is a bit strange; it's
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written to take significantly longer when the input argument is a
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factorial. The function doing the calculation is written strangely so
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that it takes significantly longer when the input argument is a
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multiple of 4.
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::
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@ -604,28 +607,31 @@ multiple of 4.
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result = queue.get()
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print 'Factorial', N, '=', result
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A :class:`Queue` object is created and stored as a global. The child
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process will use the value of the variable when the child was created;
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because it's a :class:`Queue`, parent and child can use the object to
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communicate. (If the parent were to change the value of the global
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variable, the child's value would be unaffected, and vice versa.)
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A :class:`Queue` is used to communicate the input parameter *N* and
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the result. The :class:`Queue` object is stored in a global variable.
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The child process will use the value of the variable when the child
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was created; because it's a :class:`Queue`, parent and child can use
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the object to communicate. (If the parent were to change the value of
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the global variable, the child's value would be unaffected, and vice
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versa.)
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Two other classes, :class:`Pool` and :class:`Manager`, provide
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higher-level interfaces. :class:`Pool` will create a fixed number of
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worker processes, and requests can then be distributed to the workers
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by calling :meth:`apply` or `apply_async`, adding a single request,
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and :meth:`map` or :meth:`map_async` to distribute a number of
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by calling :meth:`apply` or `apply_async` to add a single request,
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and :meth:`map` or :meth:`map_async` to add a number of
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requests. The following code uses a :class:`Pool` to spread requests
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across 5 worker processes, receiving a list of results back.
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across 5 worker processes and retrieve a list of results::
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::
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from multiprocessing import Pool
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from multiprocessing import Pool
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def factorial(N, dictionary):
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"Compute a factorial."
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...
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p = Pool(5)
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result = p.map(factorial, range(1, 1000, 10))
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for v in result:
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print v
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print v
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This produces the following output::
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@ -636,14 +642,15 @@ This produces the following output::
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33452526613163807108170062053440751665152000000000
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...
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The :class:`Manager` class creates a separate server process that can
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hold master copies of Python data structures. Other processes can
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then access and modify these data structures by using proxy objects.
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The following example creates a shared dictionary by calling the
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:meth:`dict` method; the worker processes then insert values into the
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dictionary. (No locking is done automatically, which doesn't matter
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in this example. :class:`Manager`'s methods also include
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:meth:`Lock`, :meth:`RLock`, and :meth:`Semaphore` to create shared locks.
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The other high-level interface, the :class:`Manager` class, creates a
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separate server process that can hold master copies of Python data
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structures. Other processes can then access and modify these data
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structures using proxy objects. The following example creates a
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shared dictionary by calling the :meth:`dict` method; the worker
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processes then insert values into the dictionary. (Locking is not
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done for you automatically, which doesn't matter in this example.
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:class:`Manager`'s methods also include :meth:`Lock`, :meth:`RLock`,
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and :meth:`Semaphore` to create shared locks.)
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::
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@ -686,7 +693,7 @@ This will produce the output::
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21 51090942171709440000
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31 8222838654177922817725562880000000
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41 33452526613163807108170062053440751665152000000000
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51 1551118753287382280224243016469303211063259720016986112000000000000
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51 15511187532873822802242430164693032110632597200169861120000...
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.. seealso::
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@ -716,9 +723,8 @@ The formatting template uses curly brackets (`{`, `}`) as special characters::
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"User ID: {0}".format("root") -> "User ID: root"
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# Use the named keyword arguments
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uid = 'root'
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'User ID: {uid} Last seen: {last_login}'.format(uid='root',
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'User ID: {uid} Last seen: {last_login}'.format(
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uid='root',
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last_login = '5 Mar 2008 07:20') ->
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'User ID: root Last seen: 5 Mar 2008 07:20'
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@ -736,9 +742,9 @@ supply compound field names that read attributes or access dictionary keys::
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Python version: 2.6a1+ (trunk:61261M, Mar 5 2008, 20:29:41) \n
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[GCC 4.0.1 (Apple Computer, Inc. build 5367)]'
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import mimetypes
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'Content-type: {0[.mp4]}'.format(mimetypes.types_map) ->
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'Content-type: video/mp4'
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import mimetypes
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'Content-type: {0[.mp4]}'.format(mimetypes.types_map) ->
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'Content-type: video/mp4'
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Note that when using dictionary-style notation such as ``[.mp4]``, you
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don't need to put any quotation marks around the string; it will look
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@ -753,18 +759,24 @@ adding a colon followed by a format specifier. For example::
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# Field 0: left justify, pad to 15 characters
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# Field 1: right justify, pad to 6 characters
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fmt = '{0:15} ${1:>6}'
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fmt.format('Registration', 35) ->
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'Registration $ 35'
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fmt.format('Tutorial', 50) ->
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'Tutorial $ 50'
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fmt.format('Banquet', 125) ->
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'Banquet $ 125'
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Format specifiers can reference other fields through nesting::
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fmt = '{0:{1}}'
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fmt.format('Invoice #1234', 15) ->
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width = 15
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fmt.format('Invoice #1234', width) ->
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'Invoice #1234 '
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width = 35
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fmt.format('Invoice #1234', width) ->
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'Invoice #1234 '
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@ -819,8 +831,9 @@ formatted. It receives a single argument, the format specifier::
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else:
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return str(self)
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There's also a format() built-in that will format a single value. It calls
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the type's :meth:`__format__` method with the provided specifier::
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There's also a :func:`format` built-in that will format a single
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value. It calls the type's :meth:`__format__` method with the
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provided specifier::
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>>> format(75.6564, '.2f')
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'75.66'
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@ -829,7 +842,7 @@ the type's :meth:`__format__` method with the provided specifier::
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.. seealso::
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:ref:`formatstrings`
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The reference format fields.
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The reference documentation for format fields.
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:pep:`3101` - Advanced String Formatting
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PEP written by Talin. Implemented by Eric Smith.
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