Debugging Tasks with lsstDebug

Note

See also the Doxygen documentation on lsstDebug.

In your Task code, if you import lsstDebug then call:

debug = lsstDebug.Info(__name__)

(with __name__ being the name of the current Task), you are given a “debug object”. By default that will simply give you a False for any attribute you access. Thus:

>>> debug.foo
False

>>> debug.bar
False

>>> debug.display
False

The aim is to customize the behaviour of debug to meet your particular needs. In this, you want to define a function that, when called with __name__, as an argument will provide non-False values for certain combinations of __name__ and attribute. Thus, you can do things like:

>>> debug = lsstDebug.Info(__name__)  # __name__ selects the current task
>>> debug.display
True

Then you can write your task to optionally enable a display (or whatever) by doing something like:

if debug.display:
   afwDisplay.getDisplay()....
else:
   self.log.debug("I would show you a pretty picture here if you enabled debugging.")

Refer to the task documentation and look for “debug variables” to discover what debugging options are available for existing Tasks.

In order to load your specific debugging configuration, create a debug.py in your working directory, and put something like this in it:

import lsstDebug
def DebugInfo(name):
    debug = lsstDebug.getInfo(name)
    if name == "lsst.meas.astrom.astrometry":
        debug.display = True
    return debug

lsstDebug.Info = DebugInfo

That should enable debugging the display attribute when you are running inside lsst.meas.astrom.astrometry, and disable it elsewhere. Of course, you can also return arbitrarily more complex objects, doing things like specifying the frame to display on etc.

You may use the -d command line argument to pass a path to debug.py to a command line task, rather than relying on it being found in your working directory.