Stack log messages
Stack log messages
- Documentation: https://micahjsmith.github.io/stacklog
- Homepage: https://github.com/micahjsmith/stacklog
Stacklog is a tiny Python library to stack log messages.
A stack-structured log is an approach to logging in which log messages are (conceptually)
pushed onto a stack and emitted only when the pusher returns. Stacklog provides a single
stacklog, which serves as either a decorator or a context manager. This is
exceptionally useful in small projects or one-off scripts.
This is illustrated best with an example:
with stacklog(print, 'Running some code'): with stacklog(print, 'Running some other code'): pass
This produces the following logging output:
Running some code... Running some other code... Running some other code...DONE Running some code...DONE
When the code within a stacklog context completes, the provided message is echoed along with
the return status, one of
FAILURE. That's pretty much it.
stacklog has been developed and tested on Python 2.7 and 3.4+.
pip install stacklog
How often do you find yourself using the following logging anti-pattern in Python?
import logging def a(): logging.info('Running a') do_something() logging.info('Done with a') def b(): logging.info('Running b') a() logging.info('Done with b') try: b() except: logging.info('There was an error running b')
The intention here is to log the beginning and end of procedure calls for use in debugging or user monitoring. I call this an anti-pattern because:
- it requires excessive manual attention to writing/updating logging calls at entry/exit sites
- it results in redundant exception handling logic
- the resulting log messages can be misleading if errors occur
Instead, the approach taken by stacklog is to accomplish this using only decorators and context managers.
Usage as decorator
Here is the above example using the stacklog as a decorator:
@stacklog(logging.info, 'Running a') def a(): raise Exception @stacklog(logging.info, 'Running b') def b(): a() b()
This produces logging output:
INFO:root:Running b... INFO:root:Running a... INFO:root:Running a...FAILURE INFO:root:Running b...FAILURE
Usage as context manager
Here is another example using stacklog as a context manager:
>>> with stacklog(logging.info, 'Running some code'): ... do_something() ... INFO:root:Running some code... INFO:root:Running some code...DONE
Providing custom conditions
A condition is a tuple
exception, status. If the provided exception is raised during the
execution of the provided code, the provided status is logged instead of the default
>>> with stacklog(logging.info, 'Running some code', conditions=[(NotImplementedError, 'SKIPPED')]): ... raise NotImplementedError ... INFO:root:Running some code... INFO:root:Running some code...SKIPPED
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