On 5/4/2015 1:43 PM, Ian Kelly wrote:
* () is a zero-element tuple, and (a, b) is a two-element tuple, but (a) is not a one-element tuple. Tuples are created by commas, not parentheses, so use (a,) instead.
Which means that a, and a,b (or a,b,) are 1 and 2 element tuples respectively. Except for empty tuples, parentheses are optional unless needed to fence off the tuple from surrounding code (which happens to be most of the time, but not always). A trailing comma is prohibited for zero element tuples, required for one element tuples, and optional for multiple element tuples.
-- Terry Jan Reedy -- https://mail.python.org/mailman/listinfo/python-list
