Tuple

Syntactically, a tuple is a comma-separated list of values:

t = 'a', 'b', 'c', 'd', 'e'

Although not necessary, it is common to enclose tuples in parentheses:

t = ('a', 'b', 'c', 'd', 'e')

Create an empty tuple with parentheses:

t0 = ()
type(t0)            # <type 'tuple'>

To create a tuple with a single element, you have to include a final comma:

t1 = 'a',
type(t1)              # <type 'tuple'>

Note that a single value in parentheses is not a tuple:

t2 = ('a')
type(t2)              # <type 'str'>

To create a singleton tuple it is necessary to have a trailing comma.

t2 = ('a',)
type(t2)              # <type 'tuple'>

Note that for singleton tuples it’s recommended (see PEP8 on trailing commas) to use parentheses. Also, no white space after the trailing comma (see PEP8 on whitespaces)

t2 = ('a',)           # PEP8-compliant
t2 = 'a',             # this notation is not recommended by PEP8
t2 = ('a', )          # this notation is not recommended by PEP8

Another way to create a tuple is the built-in function tuple.

t = tuple('lupins')
print(t)              # ('l', 'u', 'p', 'i', 'n', 's')
t = tuple(range(3))
print(t)              # (0, 1, 2)

These examples are based on material from the book Think Python by Allen B. Downey.