Python with Jupyter Notebook Tutorial - Lists & Tuples (HD) Part 5

Tuple: A tuple is a collection of values and it is declared using parentheses. However, we can also use a tuple packing to do the same, and unpacking to assign its values to a sequence. Lists: Unlike in C++, we don’t have arrays to work with in Python. Here, we have a list instead. Mutability a. A List is Mutable Let’s first see lists. Let’s take a new list for exemplar purposes. list1=[0,1,2,3,4,5,6,7] Now first, we’ll try reassigning an element of a list. Let’s reassign the second element to hold the value 3. list1[1]=3 list1 [0, 3, 2, 3, 4, 5, 6, 7] Again, let’s see how we can reassign the entire list. list1=[7,6,5,4,3,2,1,0] list1 [7, 6, 5, 4, 3, 2, 1, 0] It worked, great. Now, we will delete just one element from the list. del list1[1] list1 [7, 5, 4, 3, 2, 1, 0] This was easy, but could we delete a slice of the list? Let’s try it. del list1[3:] list1 [7, 5, 4] We can access a slice the same way. Can we reassign a slice? nums=[1,2,3,4,5] nums[1:3]=[6,7,8] nums [1, 6, 7, 8, 4, 5] Indeed, we can. Finally, let’s try deleting the entire list. del list1 list1 Traceback (most recent call last): File "pyshell#67", line 1, in module list1 NameError: name ‘list1’ is not defined The list doesn’t exist anymore. b. A Tuple is Immutable Now, let’s try doing the same things to a tuple. We know that a tuple is immutable, so some of these operations shouldn’t work. We’ll take a new tuple for this purpose. mytuple=0,1,2,3,4,5,6,7 First, let’s try reassigning the second element. mytuple[1]=3 Traceback (most recent call last): File "pyshell#70", line 1, in module mytuple[1]=3 TypeError: ‘tuple’ object does not support item assignment As you can see, a tuple doesn’t support item assignment. However, we can reassign an entire tuple. mytuple=2,3,4,5,6 mytuple (2, 3, 4, 5, 6) Next, let’s try slicing a tuple to access or delete it. mytuple[3:] (5, 6) del mytuple[3:] Traceback (most recent call last): File "pyshell#74", line 1, in module del mytuple[3:] TypeError: ‘tuple’ object does not support item deletion As is visible, we can slice it to access it, but we can’t delete a slice. This is because it is immutable. Can we delete a single element? del mytuple[3] Traceback (most recent call last): File "pyshell#75", line 1, in module del mytuple[3] TypeError: ‘tuple’ object doesn’t support item deletion Apparently, the answer is no. Finally, let’s try deleting the entire tuple. del mytuple mytuple Traceback (most recent call last): File "pyshell#77", line 1, in module mytuple NameError: name ‘mytuple’ is not defined So, here, we conclude that you can slice a tuple, reassign it whole, or delete it whole. But you cannot delete or reassign just a few elements or a slice. Let us proceed with more differences between python tuples vs lists. Functions Some python functions apply on both, these are- len(), max(), min(), sum(), any(), all(), sorted(). We’ll take just one example here for both containers. max((1,3,-1)) 3 max([1,3,-1]) 3 Methods Lists and tuples share the index() and count() methods. But other than those, there are a few methods that apply to lists. These are- append(), insert(), remove(), pop(), clear(), sort(), and reverse(). Let’s take an example of one of these. [1,3,2].index(3) 1 (1,3,2).index(3) 1 To get an insight into all of these methods and functions we mentioned, you should refer to our articles on lists and tuples. Tuples in a List We can store tuples in a list when we want to. mylist=[(1,2,3),(4,5,6)] type(mylist) class 'list' type(mylist[1]) class ‘tuple’ But when would we need to do this? Take an example. list(students) [(1, ‘ABC’), (2, ‘DEF’), (3, ‘GHI’)] Lists in a Tuple Likewise, we can also use a tuple to store lists. Let’s see how. mytuple=([1,2],[3,4],[5,6]) Nested Tuples A tuple may hold more tuples, and this can go on in more than two dimensions. mytuple=((1,2),(3,(4,5),(6,(7,(8,9))))) To access the element with the value 8, we write the following code. mytuple[1][2][1][1][0] 8 Nested Lists Similarly, a list may hold more lists, in as many dimensions as you want. mylist=[[1,2],[3,4]] myotherlist=[[1,2],[3,[4,5]]] To access the element with the value 5, we write the following c ode. myotherlist[1][1][1] 5