Tuple

A tuple is a comma-separated collection of objects and by conversion delimited by open and closed brackets - parentheses, (). A tuple is just like a list but a tuple is immutable - we can not alter the content of a tuple after creation, unlike a list.

Structure of a Tuple

sample_tuple = 1, 2, 3

# a tuple with brackets
tuple_with_bracket = (1, 2, 3)

# thus an empty tuple
empty_tuple = ()  # an empty list, []

# empty tuple object
tup_object = tuple()

# to verify this try type(sample_tuple) and
# type(tuple_with_bracket)
# we should see some with tuple

Note

A single element tuple, a unit tuple, can be created by simply ending the statement with a comma.

# this is also a tuple
single_element_tuple = 1,

# or
single_element_tuple = (1,)
print(type(single_element_tuple))

# but this is not a tuple
not_single_element_tuple = 1

# nor is this
not_single_element_tuple = (1)
print(type(not_single_element_tuple))

Pros and Cons of a Tuple

Most of the things (functionalities) we wish to do to a list, we may do to a tuple but know that we can not mutate a tuple. The workaround for this is to cast the tuple to a list, mutate it and cast it to a list afterwards. We should stick to using a list. We could also assign the said tuple to a new tuple.

my_tuple = (1, 2, 3)

# indexing
first_element = my_tuple[0]

# reassigning not allowed
# TypeError: 'tuple' object does not support item assignment
my_tuple[0] = 4

# len, max, min
tuple_size = len(my_tuple)

# sequence unpacking
# this is another way to unpack the tuple
# this is also feasible for a list
first_el, second_el, third_el = my_tuple

# this is just like a multiple assignment
first_el, second_el, third_el = 1, 2, 3

# nested tuple
nest_tuple = (
    my_tuple, ('john', 'mic', 'Dorris'), 'New zealand')

# can not append nor extend
# AttributeError
sample_tup = 1,
sample_tup.append(2)
sample_tup.extend((2, 3))

# but we can contatenate with +=
sample_tup += 2, 3
print(sample_tup)  # (1, 2, 3)

# What happened was that we concatenated 1, and 2, 3 and
# assigned it to sample_tup, we created a new tuple

Casting

we may cast - convert any iterable - a sequential object such as a list and string to a tuple but not a number. This is because we can not loop over a number. We could if we cast the number to a string. This can be done using tuple(sequence).

# casting a list to a tuple
my_list = [1, 2, 3]
my_tuple = tuple(my_list)

my_str = 'Hello world'
tuple_str = tuple(my_str)
print(tuple_str)
# output-> 
# ('H', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd')

Practicals

Given the line 2x - 3y + 5 = 0, print out a list of points from x and y in range of 0 to 100 such the points lie on the line and also the value for either x or y is a multiple of 3 or 5.

Summary

A tuple is an immutable list, delimited by parentheses
Sample tuple, my_tuple = (1, 2, 3)
tuple does not have the append and extend method
Make a sequence a tuple by casting it. tuple('I am a string')

Python3 Programming - Exercise 15 - Tuple