Logging, tracing, and inheritance

Release:1.3.0

Autologging’s policy on inheritance is simple:

Loggers are never inherited, and inherited methods are never traced.

Practically speaking, this means that you must be explicit when using autologging.logged and autologging.traced throughout a class’s bases.

If a class in the hierarchy will use a logger, then that class definition must be @logged. Likewise, if a method inherited from a super class in the hierarchy will be traced, then either the method must be traced in the super class or the method must be overridden (and traced) in a subclass.

The following example illustrates these concepts:

# my_module.py

from autologging import logged, traced


@traced
@logged
class Base:

   # this method will be traced
   def method(self):
      # log channel will be "my_module.Base"
      self.__log.info("base message")
      return "base"


@logged
class Parent(Base):

   # this method will NOT be traced
   def method(self):
      # log channel will be "my_module.Parent"
      self.__log.info("parent message")
      return super().method() + ",parent"


@traced
class Child(Parent):

   # this method will be traced
   def method(self):
      return super().method() + ",child"

>>> import logging, sys
>>> from autologging import TRACE
>>> logging.basicConfig(level=TRACE, stream=sys.stdout,
...     format="%(levelname)s:%(name)s:%(funcName)s:%(message)s")
>>> from my_module import Child
>>> child = Child()
>>> child.method()
TRACE:my_module.Child:method:CALL *() **{}
INFO:my_module.Parent:method:parent message
TRACE:my_module.Base:method:CALL *() **{}
INFO:my_module.Base:method:base message
TRACE:my_module.Base:method:RETURN 'base'
TRACE:my_module.Child:method:RETURN 'base,parent,child'
'base,parent,child'