Python Arrays - ideasorblogs

In Python, arrays are created using the list data type. A list is a collection of items that are ordered and changeable. Lists are written with square brackets and the items are separated by commas.

Here is an example of a list in Python:


my_list = [1, 2, 3, 4]

You can access the items on a list using the index number of the item in the list. The index numbers start at 0 for the first item.


# Access the first item in the list

first_item = my_list[0]

print(first_item) # Output: 1


# Access the third item in the list

third_item = my_list[2]

print(third_item) # Output: 3

You can also use negative index numbers to access items from the end of the list. For example, the index number -1 refers to the last item in the list, -2 refers to the second last item, and so on.


# Access the last item in the list

last_item = my_list[-1]

print(last_item) # Output: 4


# Access the second last item in the list

second_last_item = my_list[-2]

print(second_last_item) # Output: 3

You can also use index numbers to modify the value of an item in a list.


# Modify the value of the first item in the list

my_list[0] = 10

print(my_list) # Output: [10, 2, 3, 4]

You can use the len() function to find the length of a list.


# Find the length of the list

list_length = len(my_list)

print(list_length) # Output: 4

You can use the append() method to add a new item to the end of a list.


# Add a new item to the end of the list

my_list.append(5)

print(my_list) # Output: [10, 2, 3, 4, 5]

You can use the insert() method to add a new item at a specific index in the list.


# Add a new item at index 1

my_list.insert(1, 0)

print(my_list) # Output: [10, 0, 2, 3, 4, 5]

You can use the remove() method to remove an item from the list.


# Remove the item at index 2

my_list.remove(2)

print(my_list) # Output: [10, 0, 3, 4, 5]

You can use the pop() method to remove and return the last item from the list.


# Remove and return the last item from the list

last_item = my_list.pop()

print(last_item) # Output: 5

print(my_list) # Output: [10, 0, 3, 4]

You can use the clear() method to remove all items from the list.


# Remove all items from the list

my_list.clear()

print(my_list) # Output: []

You can use the index() method to find the index of an item in the list.


my_list = [10, 3, 4]

# Find the index of the item 4

index_of_item_4 = my_list.index(4)

print(index_of_item_4) # Output: 2

You can use the count() method to count the number of occurrences of an item in the list.


# Count the number of occurrences of the item 10

count_of_item_10 = my_list.count(10)

print(count_of_item_10) # Output: 1

You can use the sort() method to sort the items of the list in ascending order.


my_list = [10, 3, 4, 5, 1]

# Sort the list in ascending order

my_list.sort()

print(my_list) # Output: [1, 3, 4, 5, 10]

You can also use the reverse() method to reverse the order of the items in the list.


# Reverse the order of the items in the list

my_list.reverse()

print(my_list) # Output: [10, 5, 4, 3, 1]

Table of array methods in Python

Method	Description
`append()`	Add an item to the end of the list
`clear()`	Remove all items from the list
`copy()`	Return a copy of the list
`count()`	Return the number of occurrences of an item in the list
`extend()`	Add all items from an iterable to the end of the list
`index()`	Return the index of the first occurrence of an item in the list
`insert()`	Insert an item at a specific index in the list
`pop()`	Remove and return the item at a specific index in the list (default is the last item)
`remove()`	Remove the first occurrence of an item from the list
`reverse()`	Reverse the order of the items in the list
`sort()`	Sort the items of the list in ascending order