What is the syntax rule for having trailing commas in tuple definitions?

Question

In the case of a single element tuple, the trailing comma is required.

a = (\'foo\',)

What about a tuple with multiple elements? It seems t

Answer 1

Another reason that this exists is that it makes code generation and __repr__ functions easier to write. For example, if you have some object that is built like obj(arg1, arg2, ..., argn), then you can just write obj.__repr__ as

def __repr__(self):
    l = ['obj(']
    for arg in obj.args: # Suppose obj.args == (arg1, arg2, ..., argn)
        l.append(repr(arg))
        l.append(', ')
    l.append(')')
    return ''.join(l)

If a trailing comma wasn't allowed, you would have to special case the last argument. In fact, you could write the above in one line using a list comprehension (I've written it out longer to make it easier to read). It wouldn't be so easy to do that if you had to special case the last term.