noop() returns something

YAGNI.

This is rejected because it complicates the semantics. For example, if you always return both *args and **kws, what do you return when none of those are given? Returning a tuple of ((), {}) is kind of ugly, but provides consistency. But you might also want to just return None since that’s also conceptually what the function was passed.

Or, what if you pass in exactly one positional argument, e.g. noop(7). Do you return 7 or ((7,), {})? And so on.

The author claims that you won’t ever need the return value of noop() so it will always return None.

Coghlan’s Dialogs (edited for formatting):

My counterargument to this would be map(noop, iterable), sorted(iterable, key=noop), etc. (filter, max, and min all accept callables that accept a single argument, as do many of the itertools operations).

Making noop() a useful default function in those cases just needs the definition to be:

def noop(*args, **kwds):
    return args[0] if args else None

The counterargument to the counterargument is that using None as the default in all these cases is going to be faster, since it lets the algorithm skip the callback entirely, rather than calling it and having it do nothing useful.