What exactly is "pass"? What should it be?

[John Ladasky]

Hi folks,

I'm trying to write tidy, modular code which includes a long-running process.  From time to time I MIGHT like to check in on the progress being made by that long-running process, in various ways.  Other times, I'll just want to let it run.  So I have a section of code which, generally, looks like this:

def _pass(*args):
    pass

def long_running_process(arg1, arg2, arg_etc, report = _pass):
    result1 = do_stuff()
    report(result1)
    result2 = do_some_different_stuff()
    report(result2)
    result3 = do_even_more_stuff()
    report(result3)
    return result3

This does what I want.  When I do not specify a report function, the process simply runs.  Typically, when I do supply a report function, it would print something to stdout, or draw an update through a GUI.

But this approach seems a tad cumbersome and unPythonic to me, particularly the part where I define the function _pass() which accepts an arbitrary argument list, and does nothing but... pass.

This has led me to ask the question, what exactly IS pass?  I played with the interpreter a bit.

IDLE 2.6.6      ==== No Subprocess ====
>>> pass
>>> pass()
SyntaxError: invalid syntax
>>> type(pass)
SyntaxError: invalid syntax

So, pass does not appear to be a function, nor even an object.  Is it nothing more than a key word?

And would there be any merit to having some syntactic sugar which allows pass to behave like the _pass() function I wrote, if it were called?

As you can see, I'm programming in Python 2.6.  I don't know whether pass is handled differently in Python 3.