✨Collections In Python :-List✨

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Contents of this blog:

1. collection data types which are supported by Python
2. List
3. Defining a List
4. List Indexing
5. Accessing the List element
6. Concatenation of Two list
7. List Iteration
8. List built-in function

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There are many collection data types which are supported by Python.

• List
• Tuple
• String
• Set
• Dictionary

List :

List can be used to store a group of elements together in a sequence.

list stores a series of items in a particular order. You access items using an index.

Real life Example :

You can use a List to store the ingredients to cook a chicken, because Lists support sequential access and you can access the steps in order.

Defining a List :

Use square brackets( [] )to define a list, and use commas(,) to separate individual items in the list.

Making a list

users = [“shruti”,“vishal”, “bobby”, “rony”, “kamal”]

List Indexing :

• Each element in the list has a position in the list known as an index.
• The list index starts from zero.

Creating a Empty List :

>>> empty_list = []
>>> empty_list = list()

• Create a list with Known element & Known size :

>>> sample_list = [1,2,3,4,5]

• Create a list with Known element & Unknown size :

>>> sample_list = [None]*5
                     |
                     |
                     ---->   None denotes an unknown value.

Accessing the List element :

• Individual elements in a list are accessed according to their position, called the index. The index of the first element is 0, the index of the second element is 1, and so forth.
• Negative indices refer to items at the end of the list. To get a particular element, write the name of the list and then the index of the element in square brackets.
• List can store both Homogeneous and heterogeneous elements.
• Syntax of Accessing list element of list :

>>> list_name[index]
>>> users[0]    # It gives you First element of list. i.e. "shruti"
>>> users[1]    # It gives you Second element of list. i.e. "vishal"
>>> users[-1]   # It gives you last element of list.

Length of list :

>>> sample_list = [1,2,3,4,5]
>>> len(sample_list)  # len(collection) : Syntax

Concatenation of Two list :

>>> sample_list = [1,2,3,4,5]
>>> sample_list1 = [6,7,8,9,10]
>>> sample_list = sample_list + sample_list1  
     # '+' --> used to     concatenation

List Iteration:

>>> users = ["shruti", "Ronny", "Razz", "Ram", "hari"]
# 1st way by index
>>>for index in range(0,len(users)):
       print(users[index])
# 2nd way by 'in' keyword
>>>for user in users:
       print(user)

Modifying the elements in list :

Once you’ve defined a list, you can change individual elements in the list. You do this by referring to the index of the item you want to modify.

>>> users[2] = “razz”  # It will modify 3rd element of list.
>>> users[-1] = “rahul” # It will modify last element of list.

List Slicing :

if requirement is sublist from a list with limited no of element.

Syntax :

list[start : end :jump]

• start → starting index(by default = 0)
• end → ending index (by default = len(list)), it is exclusive.
• jump/step (by default jump = 1)

e.g :

we have list of 6 elements :

>>>list3 = [1,2,3,4,5,6]

• if you want element from index 1 to index 3 as sub-list, so we need to apply slicing here:

>>>list3[1:4]   # start = 1 , end = 3+1 , jump = 1

• if you want element from start to end but jump would be 2 as sub-list

• Reverse the list without using reverse function:

List built-in function :

1. append(element) : Add element to end of list.

2. insert(position,element) :Insert an element at specific position.

3. index(element) : Return the First occurrence index of element. if not found then throw valueError.

4. pop(index) : Remove & returns an element at given index position.

5. remove(element) : Remove first occurrence of element.

6. sort() : Sort list in ascending order.

7. reverse() : It will reverse the list.

Thank you…