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
tupleis an immutable list, delimited by parentheses - Sample tuple,
my_tuple = (1, 2, 3) -
tupledoes not have theappendandextendmethod - Make a sequence a
tupleby casting it.tuple('I am a string')
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