What are tuples?

- Tuples are another type of sequence in Python

- they are immutable

- they can be packed

- they can be unpacked to variables

- they can contain mutable objects

- lightweight compared to lists

Demo on how to use tuples

        >>> t = 12345, 54321, 'hello!'

>>> t[0]

12345

>>> t

(12345, 54321, 'hello!')

>>> # Tuples may be nested:

... u = t, (1, 2, 3, 4, 5)

>>> u

((12345, 54321, 'hello!'), (1, 2, 3, 4, 5))

>>> # Tuples are immutable:

... t[0] = 88888

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

TypeError: 'tuple' object does not support item assignment

>>> # but they can contain mutable objects:

... v = ([1, 2, 3], [3, 2, 1])

>>> v

([1, 2, 3], [3, 2, 1])

Ways on defining an empty tuple and a tuple with only 1 element

        >>> empty = ()

>>> singleton = 'hello',    # <-- note trailing comma

>>> len(empty)

0

>>> len(singleton)

1

>>> singleton

('hello',)

Packing and unpacking a tuple

        >>> t = 23, 'grapes', 'linux'  # packing a tuple

>>> t

(23, 'grapes', 'linux')

>>>

>>> number, fruit, os = t  # unpacking a tuple

>>> number

23

>>> fruit

'grapes'

>>> os

'linux'

>>>

>>> number, fruit, os, car = t      # number of variables on the left side must match

Traceback (most recent call last):  # the number of elements on the right tuple

  File "<stdin>", line 1, in <module>

ValueError: not enough values to unpack (expected 4, got 3)

>>>

Tuples can be converted to list and vice-versa

        >>> secret_message = "hello world"

>>> list(secret_message)

['h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd']

>>> tuple(secret_message)

('h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd')

>>> list(tuple(list(secret_message)))

['h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd']

>>> ''.join(list(tuple(list(secret_message))))

'hello world'

You can also do comparison between tuples

        >>> t1

(1, 5, 7.6)

>>> t2

(2, 8, 100)

>>>

>>> t1 < t2

True

>>>

>>> t1 > t2

False

You cannot delete a specific element in a tuple but you can delete all of them at once

        >>> num = 600, 1, 5, 45.6

>>> num

(600, 1, 5, 45.6)

>>> del num[2]

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

TypeError: 'tuple' object doesn't support item deletion

>>> del num

>>> num

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

NameError: name 'num' is not defined

>>>

Other operations that can be done on tuples

        >>> len((1, 2, 3))  # length

3

>>> (1, 2, 3) + (4, 5, 6)  # addtion (concatenation)

(1, 2, 3, 4, 5, 6)

>>> ('Hi!',) * 4  # repetition

('Hi!', 'Hi!', 'Hi!', 'Hi!')

>>> 3 in (1, 2, 3)  # membership

True

>>> for x in (1,2,3) : print (x, end = ' ')  # iteration

...

1 2 3 >>>

>>>

Since tuples are also sequences, you can do slice and index operations against them

        >>> T=('C++', 'Java', 'Python')

>>> T[2]

'Python'

>>> T[-2]

'Java'

>>> T[1:]

('Java', 'Python')

>>>

Other tuple functions

        cmp(tuple1, tuple2)

len(tuple)

max(tuple)

min(tuple)

tuple(seq)