One of the most inconsistent part of the Python syntax is tuple literals. Basically, to create a tuple you just write values separated by commas: 1, 2, 3. OK, so far, so good. What about tuple containing only one element? You just add trailing comma to the only value: 1,. Well, that’s somewhat ugly and error prone, but makes sense. What about empty tuple? Is it a bare ,? No, it’s (). Do parentheses create tuple as well as commas? No, they don’t, (4) is not a tuple, it’s just 4. In : a = [ ...: (1, 2, 3), ...: (1, 2), ...: (1), ...: (), ...: ] In : [type(x) for x in a] Out: [tuple, tuple, int, tuple] To make things more obscure, tuple literals often require additional parentheses. If you want a tuple to be the only argument of a function, that f(1, 2, 3) doesn’t work for an obvious reason, you need f((1, 2, 3)) instead.