Wax On, Wax Off

Often it’s convenient to only display debugging information under some conditions, but not others, such as when a debug flag is set. That often leads to multi-line conditionals such as:

if debug:
    print "x:", x, "y:", y, "z:", z

With show it’s a bit easier. There’s a keyword argument, also called show, that controls whether anything is shown. If it’s truthy, it shows; falsy, ad it doesn’t:

show(x, y, z, show=debug)

You can set the show flag more globally:

show.set(show=False)

You can also make multiple show instances that can be separately controlled:

show_verbose = show.clone()
show_verbose.set(show=verbose_flag)
show_verbose(x, y, z)

For a more fire-and-forget experience, try setting visibility with a lambda parameter:

debug = True
show.set(show=lambda: debug)

Then, whenever debug is truthy, values will be shown. When debug is falsy, values will not be shown.

When you really, truly want show‘s output to disappear, and want to minimize overhead, but don’t want to change your source code (lest you need those debug printing statements again shortly), try:

show = noshow

This one line will replace the show object (and any of its clones) with parallel NoShow objects that simply don’t do anything or print any output.

Note

This assignment should be done in a global context. If done inside a function, you’ll need to add a corresponding global show declaration.

As an alternative, you can:

from show import show
from show import noshow as show

Then comment out the``noshow`` line for debugging, or the show line for production runs.

Note

A little care is required to configure global non-showing behavior if you’re using show‘s function decorators such as @show.inout. Decorators are evaluated earlier in program execution than the “main flow” of program execution, so it’s a good idea to define the lambda or noshow control of visibility at the top of your program.