Merged documentation update from 3.3.

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Vinay Sajip 2014-01-17 18:36:41 +00:00
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@ -1918,3 +1918,31 @@ something, you can make it more palatable if you use an alias such as ``M`` or
``_`` for the message (or perhaps ``__``, if you are using ``_`` for ``_`` for the message (or perhaps ``__``, if you are using ``_`` for
localization). localization).
Examples of this approach are given below. Firstly, formatting with
:meth:`str.format`::
>>> __ = BraceMessage
>>> print(__('Message with {0} {1}', 2, 'placeholders'))
Message with 2 placeholders
>>> class Point: pass
...
>>> p = Point()
>>> p.x = 0.5
>>> p.y = 0.5
>>> print(__('Message with coordinates: ({point.x:.2f}, {point.y:.2f})', point=p))
Message with coordinates: (0.50, 0.50)
Secondly, formatting with :class:`string.Template`::
>>> __ = DollarMessage
>>> print(__('Message with $num $what', num=2, what='placeholders'))
Message with 2 placeholders
>>>
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
handler. So the only slightly unusual thing which might trip you up is that the
parentheses go around the format string and the arguments, not just the format
string. Thats because the __ notation is just syntax sugar for a constructor
call to one of the ``XXXMessage`` classes shown above.