Logging

Mix in LoggingArgs to get verbosity flags and a configured logger for free.

import duho
from duho import LoggingArgs

class App(LoggingArgs):
    """Do the thing."""

    target: str
    "What to act on"
    ("--target",)

    def __call__(self):
        self._logger_.info("working on %s", self.target)
        self._logger_.debug("some detail")

if __name__ == "__main__":
    raise SystemExit(duho.main(App))

duho.main calls self._set_loglevels_() before dispatching, so by the time __call__ runs the levels are applied. (Pass setup_logging=False to opt out; if you drive the parser yourself, call _set_loglevels_() before you start logging.)

The flags

LoggingArgs adds:

Flag	Effect
-v, -vv, …	More verbose: INFO → DEBUG → TRACE
-q, -qq, …	Quieter: INFO → WARNING → ERROR → CRITICAL
--loglevel LEVEL	Set a level explicitly
--loglevel mod:LEVEL	Set a level for one module

$ app --target x -v                     # DEBUG
$ app --target x -vv                    # TRACE
$ app --target x -q                     # WARNING
$ app --target x --loglevel DEBUG
$ app --target x --loglevel urllib3:WARNING,myapp:TRACE

-v and -q are counted flags that move in opposite directions from the default INFO, and they offset each other (-vv -q nets one step more verbose). Both ends of the scale clamp rather than wrapping or erroring.

Colored output

duho.init_stderr_logging() installs a handler with DefaultFormatter, which colors the level name. If colorama is installed it's used for Windows compatibility; otherwise duho emits raw ANSI codes.

pip install duho[colorama]

The TRACE level

duho registers a TRACE level below DEBUG:

logger.trace("very fine detail")

Add your own levels with duho.add_logging_level:

import duho

duho.add_logging_level("NOTICE", 25, color="cyan")

The new level is usable as logger.notice(...), participates in the -v/-q scale, and is accepted by --loglevel.

Naming the logger

self._logger_ is scoped to the parser's name. Override it with _logger_name_:

class App(LoggingArgs):
    _logger_name_ = "myapp.cli"