logging: Added getChild utility method to Logger and added isEnabledFor method to LoggerAdapter.

Doc/library/logging.rst

@@ -894,6 +894,16 @@ instantiated directly, but always through the module-level function
    :const:`NOTSET` is found, and that value is returned.
 
 
+.. method:: Logger.getChild(suffix)
+
+   Returns a logger which is a descendant to this logger, as determined by the suffix.
+   Thus, ``logging.getLogger('abc').getChild('def.ghi')`` would return the same
+   logger as would be returned by ``logging.getLogger('abc.def.ghi')``. This is a
+   convenience method, useful when the parent logger is named using e.g. ``__name__``
+   rather than a literal string.
+
+   .. versionadded:: 2.7
+
 .. method:: Logger.debug(msg[, *args[, **kwargs]])
 
    Logs a message with level :const:`DEBUG` on this logger. The *msg* is the
@@ -2472,6 +2482,11 @@ methods of :class:`Logger`, i.e. :meth:`debug`, :meth:`info`, :meth:`warning`,
 methods have the same signatures as their counterparts in :class:`Logger`, so
 you can use the two types of instances interchangeably.
 
+.. versionchanged:: 2.7
+
+The :meth:`isEnabledFor` method was added to :class:`LoggerAdapter`. This method
+delegates to the underlying logger.
+
 
 Thread Safety
 -------------

Lib/logging/__init__.py

@@ -1316,6 +1316,25 @@ class Logger(Filterer):
             return 0
         return level >= self.getEffectiveLevel()
 
+    def getChild(self, suffix):
+        """
+        Get a logger which is a descendant to this one.
+
+        This is a convenience method, such that
+
+        logging.getLogger('abc').getChild('def.ghi')
+
+        is the same as
+
+        logging.getLogger('abc.def.ghi')
+
+        It's useful, for example, when the parent logger is named using
+        __name__ rather than a literal string.
+        """
+        if self.root is not self:
+            suffix = '.'.join((self.name, suffix))
+        return self.manager.getLogger(suffix)
+
 class RootLogger(Logger):
     """
     A root logger is not that different to any other logger, except that
@@ -1420,6 +1439,12 @@ class LoggerAdapter(object):
         msg, kwargs = self.process(msg, kwargs)
         self.logger.log(level, msg, *args, **kwargs)
 
+    def isEnabledFor(self, level):
+        """
+        See if the underlying logger is enabled for the specified level.
+        """
+        return self.logger.isEnabledFor(level)
+
 root = RootLogger(WARNING)
 Logger.root = root
 Logger.manager = Manager(Logger.root)

Lib/test/test_logging.py

@@ -1736,6 +1736,23 @@ class ManagerTest(BaseTest):
         self.assertEqual(logged, ['should appear in logged'])
 
 
+class ChildLoggerTest(BaseTest):
+    def test_child_loggers(self):
+        r = logging.getLogger()
+        l1 = logging.getLogger('abc')
+        l2 = logging.getLogger('def.ghi')
+        c1 = r.getChild('xyz')
+        c2 = r.getChild('uvw.xyz')
+        self.assertTrue(c1 is logging.getLogger('xyz'))
+        self.assertTrue(c2 is logging.getLogger('uvw.xyz'))
+        c1 = l1.getChild('def')
+        c2 = c1.getChild('ghi')
+        c3 = l1.getChild('def.ghi')
+        self.assertTrue(c1 is logging.getLogger('abc.def'))
+        self.assertTrue(c2 is logging.getLogger('abc.def.ghi'))
+        self.assertTrue(c2 is c3)
+
+
 # Set the locale to the platform-dependent default.  I have no idea
 # why the test does this, but in any case we save the current locale
 # first and restore it at the end.
@@ -1744,7 +1761,8 @@ def test_main():
     run_unittest(BuiltinLevelsTest, BasicFilterTest,
                  CustomLevelsAndFiltersTest, MemoryHandlerTest,
                  ConfigFileTest, SocketHandlerTest, MemoryTest,
-                 EncodingTest, WarningsTest, ConfigDictTest, ManagerTest)
+                 EncodingTest, WarningsTest, ConfigDictTest, ManagerTest,
+                 ChildLoggerTest)
 
 if __name__ == "__main__":
     test_main()

Misc/NEWS

@@ -29,6 +29,9 @@ Core and Builtins
 Library
 -------
 
+- logging: Added getChild utility method to Logger and added isEnabledFor
+  method to LoggerAdapter.
+
 - Issue #8201: logging: Handle situation of non-ASCII and Unicode
   logger names existing at the same time, causing a Unicode error
   when configuration code attempted to sort the existing loggers.