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author | Vinay Sajip <vinay_sajip@yahoo.co.uk> | 2014-01-17 18:36:02 (GMT) |
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committer | Vinay Sajip <vinay_sajip@yahoo.co.uk> | 2014-01-17 18:36:02 (GMT) |
commit | eb14deca15673b77deb6f5d6dc54d3dd6a4cfb99 (patch) | |
tree | 8aff854437af20b1ff5b983adadc9e9e819f9d7b /Doc | |
parent | 6f8e81ada9741ca0db21f5a1f4b4fae85d369b06 (diff) | |
download | cpython-eb14deca15673b77deb6f5d6dc54d3dd6a4cfb99.zip cpython-eb14deca15673b77deb6f5d6dc54d3dd6a4cfb99.tar.gz cpython-eb14deca15673b77deb6f5d6dc54d3dd6a4cfb99.tar.bz2 |
Added example to recently added cookbook entry.
Diffstat (limited to 'Doc')
-rw-r--r-- | Doc/howto/logging-cookbook.rst | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/Doc/howto/logging-cookbook.rst b/Doc/howto/logging-cookbook.rst index 126e712..674695b 100644 --- a/Doc/howto/logging-cookbook.rst +++ b/Doc/howto/logging-cookbook.rst @@ -1920,3 +1920,31 @@ 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 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. That’s because the __ notation is just syntax sugar for a constructor +call to one of the ``XXXMessage`` classes shown above. |