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Merged cookbook improvement from 3.2.

This commit is contained in:
Vinay Sajip 2012-02-28 08:06:01 +00:00
parent 86798d4ff9 39b83ac772
commit ff4b7bfaef
1 changed files with 11 additions and 6 deletions
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17
Doc/howto/logging-cookbook.rst
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@ -972,12 +972,13 @@ Use of alternative formatting styles
When logging was added to the Python standard library, the only way of
formatting messages with variable content was to use the %-formatting
method. Since then, Python has gained two new formatting approaches:
string.Template (added in Python 2.4) and str.format (added in Python 2.6).
:class:`string.Template` (added in Python 2.4) and :meth:`str.format`
(added in Python 2.6).
Logging now (as of 3.2) provides improved support for these two additional
formatting styles. The :class:`Formatter` class been enhanced for Python 3.2 to
take an additional, optional keyword parameter named ``style``. This defaults
to ``'%'``, but other possible values are ``'{'`` and ``'$'``, which correspond
Logging (as of 3.2) provides improved support for these two additional
formatting styles. The :class:`Formatter` class been enhanced to take an
additional, optional keyword parameter named ``style``. This defaults to
``'%'``, but other possible values are ``'{'`` and ``'$'``, which correspond
to the other two formatting styles. Backwards compatibility is maintained by
default (as you would expect), but by explicitly specifying a style parameter,
you get the ability to specify format strings which work with
@ -1068,7 +1069,7 @@ they're declared in a module called ``wherever``):
.. code-block:: pycon
>>> from wherever import BraceMessage as __
>>> print(__('Message with {0} {1}', 2, 'placeholders'))
>>> print(__('Message with {0} {name}', 2, name='placeholders'))
Message with 2 placeholders
>>> class Point: pass
...
@ -1083,6 +1084,10 @@ they're declared in a module called ``wherever``):
Message with 2 placeholders
>>>
While the above examples use ``print()`` to show how the formatting works, you
would of course use ``logger.debug()`` or similar to actually log using this
approach.
One thing to note is that you pay no significant performance penalty with this
approach: the actual formatting happens not when you make the logging call, but
when (and if) the logged message is actually about to be output to a log by a