Python Lists (With Examples)

 PYTHON LISTS:

In Python, a list is a built-in data structure that allows you to store and manage a collection of items, which can be of any data type, including other lists. Lists are ordered, mutable, and can contain duplicate elements. Lists are defined using square brackets [], and individual elements within the list are separated by commas.

Python Lists

LIST DECLARATION:

                                          # Creating a list with some initial elements

                                          fruits = ['apple', 'banana', 'orange']

                                           # Sorting the list in alphabetical order

                                           fruits.sort()

                                           # Reversing the order of elements

                                           fruits.reverse()

                                            # Creating an empty list

                                            empty_list = []

                                            # Creating a list with repeat elements

                                            repeated = [0] * 5

                                            # Using list comprehension to create a list of squares

                                            squares = [x ** 2 for x in range(1, 6)]

                                            # Creating a nested list

                                            matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

                                            # Creating a list from an iterable using the list() constructor

                                            numbers_list = list(range(1, 6))

                                            # Printing the results

                                            print("Fruits:", fruits)

                                            print("Popped Fruit:", popped_fruit)

                                            print("Empty List:", empty_list)

                                            print("Repeated List:", repeated)

                                            print("Squares:", squares)

                                            print("Matrix:", matrix)

                                            print("Numbers List:", numbers_list)

CHARACTERISTICS OF PYTHON: 

1. Ordered: Lists maintain the order of elements as they are added, allowing predictable access by index.
2. Mutable: Lists can be changed after creation, enabling the addition, modification, or removal of elements.
3. Heterogeneous Elements: Lists can hold diverse data types, accommodating numbers, strings, booleans, and more within a single list.
4. Variable Length: Lists can dynamically grow or shrink in size, accommodating varying numbers of elements.
5. Indexing and Slicing: Elements in a list are accessed by index, with the option to extract sublists using slicing.
6. Iterability: Lists are iterable, allowing you to loop through their elements using iteration constructs like for loops.

INDEXING AND SLICING:

  1. Indexing:

• Indexing allows you to access individual elements of a list using their position (index).
• The index starts from 0 for the first element, and it increments by 1 for each subsequent element.
• You can also use negative indices to count from the end of the list.

2. Slicing:

• Slicing allows you to extract a portion (sublist) from a list.
• The syntax for slicing is a list[start: end], where the start is inclusive and the end is exclusive.
• If you omit start, slicing starts from the beginning; if you omit end, slicing goes to the end of the list.

EXAMPLE:

                                    # Define a list of fruits

                                    fruits = ['apple', 'banana', 'orange', 'grape', 'kiwi']

                                     # Indexing Explanation

                                     # Accessing individual elements using indices

                                     first_fruit = fruits[0]   # Element at index 0: 'apple'

                                     third_fruit = fruits[2]   # Element at index 2: 'orange'

                                     last_fruit = fruits[-1]   # Last element using a negative index: 'kiwi'

                                     second_last_fruit = fruits[-2]  # Second-to-last element using a negative index:                                           'grape'

                                     # Slicing Explanation

                                     # Extracting sublists using slicing

                                     sublist_1 = fruits[1:4]   # Elements from index 1 to 3 (4 is exclusive): ['banana',                                       'orange', 'grape']

                                     sublist_2 = fruits[:3]    # Elements from the beginning to index 2: ['apple',                                                 'banana', 'orange']

                                      sublist_3 = fruits[2:]    # Elements from index 2 to the end: ['orange', 'grape',                                             'kiwi']

                                      sublist_4 = fruits[0:5:2]  # Every second element from index 0 to 4: ['apple',                                              'orange', 'kiwi']

                                       # Length and Last Element Explanation

                                       # Getting the length of the list and accessing the last element

                                       length_of_fruits = len(fruits)  # Length of the list: 5

                                       last_element = fruits[-1]       # Last element using a negative index: 'kiwi'

                                       # Print the results

                                       print("Indexing:")

                                       print("First Fruit:", first_fruit)

                                       print("Third Fruit:", third_fruit)

                                       print("Last Fruit:", last_fruit)

                                       print("Second-to-Last Fruit:", second_last_fruit)

                                       print("\nSlicing:")

                                       print("Sublist 1:", sublist_1)

                                       print("Sublist 2:", sublist_2)

                                       print("Sublist 3:", sublist_3)

                                       print("Sublist 4:", sublist_4)

                                       print("\nLength and Last Element:")

                                       print("Length of Fruits List:", length_of_fruits)

                                       print("Last Element:", last_element)

UPDATING LIST VALUES:

Updating values in a list involves modifying the content of a specific element at a given index. Lists in Python are mutable, so you can change their elements after creation.

EXAMPLE:

BUILT-IN FUNCTION:

Sr.No.	Function with Description
1	cmp(list1, list2) Compares elements of both lists.
2	len(list) Gives the total length of the list.
3	max(list) Returns item from the list with max value.
4	min(list) Returns item from the list with min value.
5	list(seq) Converts a tuple into list.

 HERE ARE SOME OTHER ADDITIONAL METHOD:

Sr.No.	Methods with Description
1	list.append(obj) Appends object obj to list
2	list.count(obj) Returns count of how many times obj occurs in list
3	list.extend(seq) Appends the contents of seq to list
4	list.index(obj) Returns the lowest index in list that obj appears
5	list.insert(index, obj) Inserts object obj into list at offset index
6	list.pop(obj=list[-1]) Removes and returns last object or obj from list
7	list.remove(obj) Removes object obj from list
8	list.reverse() Reverses objects of list in place
9	list.sort([func]) Sorts objects of list, use compare func if given