Python switch statement

Having a bit of fun at 3 in the morning.

The Python version of the C-style switch statement is either a bunch of if/else's or a dictionary. Going the dictionary route can be ugly looking (not to mention confusing, pulling a value out of a mapping and calling it). This just encapsulates the whole thing and adds some support for a pseudo-default case.

The structure is a bit weird, nowhere near as nice as regular syntax, but if you absolutely have to do this, it makes it easier to read.

	"""A simple function (roughly) implementing C-style switch statements.
	Usage::
	switch(value, {
	'it':
	"You said the word!",
	'fruit':
	"Suppose he's got a pointed stick.",
	'camelot':
	"'Tis a silly place.",
	Ellipsis:
	("You've got two empty halves of coconut and you're " +
	"bangin' 'em together.")
	})
	Also accepts *args and **kwargs, which will get passed on to the
	specified case if it is callable.
	The result of the callable is returned, as is the value of
	non-callables.
	Since `default` isn't a built-in name (and obviously not a statement),
	the under-used built-in singleton Ellipsis is used in its place under
	the assumption that it is unlikely to be used as a real case.
	Fortunately, in the event that it *is* used as a real case, using
	Ellipsis as the switch value will properly select the Ellipsis case.
	Unfortunately, so will a non-match. It's probably best you don't use
	Ellipse as a real case.
	Finally: implicit break, no fall-through at all. Ever. First of all,
	dict isn't ordered, so fall-through would be weird. Second, I'm not
	going to specialize for OrderedDict (plus it would look weird on your
	end), and third, I have no idea how to put breaking in if I did. If you
	want this, do it yourself.
	"""
	def switch(value, cases, *args, **kwargs):
	try:
	case = cases[value]
	except TypeError:
	raise TypeError("Cases must be scriptable.")
	except KeyError:
	case = cases[Ellipsis] if Ellipsis in cases else None
	finally:
	try:
	return case(*args, **kwargs)
	except TypeError:
	return case
	def main():
	import sys
	try:
	value = sys.argv[1]
	except IndexError:
	value = None
	print switch(value, {
	'it':
	"You said the word!",
	'fruit':
	"Suppose he's got a pointed stick.",
	'camelot':
	"'Tis a silly place.",
	Ellipsis:
	("You've got two empty halves of coconut and you're " +
	"bangin' 'em together.")
	})
	if __name__ == "__main__":
	main()

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