[Tutor] single underscore convention?

[Eugene Leitl]

I'm hacking some random tree code, attempting to dump a tree as a HTML
table. The code snippet I'm using has:

if __name__ == "__main__":

	blah blah blah


	_def _test1():
        	print animals[0]    # print Mammals
        	animals.printtree()

	blah blah blah

	_test1()



Why the underscore, is this a convention?