Why is a tuple of tuples of length 1 not actually a tuple unless I add a comma?

Question

Given a tuple of tuples T:

((\'a\', \'b\'))

and an individual tuple t1:

(\'a\',\'b\')
         


        

Answer 1

The problem is because T is not a tuple of tuples, it is just a tuple. The comma makes a tuple, not the parentheses. Should be:

>>> T = (('a','b'),)
>>> t1 = ('a', 'b')
>>> t1 in T
True

In fact, you can loose the outer parentheses:

>>> T = ('a','b'),
>>> t1 = 'a','b'
>>> type(T)

>>> type(T[0])

>>> type(t1)

>>> t1 in T
True

Although sometimes they are needed for precedence, if in doubt put them in. But remember, it is the comma that makes it a tuple.