Lists in Python
In Python, there is no notion of fixed-size arrays. Instead, Python provides a more flexible and powerful data structure called a list.
A list is a collection of items that are ordered and changeable. Lists are defined by enclosing the elements in square brackets [].
my_list = [1, 2, 3, 4, 5]
A list can contain elements of different data types.
mixed_list = [1, 2.5, "hello", [5, 6, 7]]
Lists can be accessed by index, mutable, and can be sliced.
Note that they are zero-indexed, meaning that the first element is at index 0.
my_list = [1, 2, 3, 4, 5]
print(my_list[0]) # Output: 1
my_list[0] = 10
print(my_list) # Output: [10, 2, 3, 4, 5]
print(my_list[1:3]) # Output: [2, 3]
Lists can be concatenated using the + operator.
list = [1, 2, 3] + [4, 5, 6]
print(list) # Output: [1, 2, 3, 4, 5, 6]
We can also use the * operator to repeat the elements of a list.
list = [1, 2, 3] * 3
print(list) # Output: [1, 2, 3, 1, 2, 3, 1, 2, 3]
To access the length of a list, we can use the len() function.
my_list = [1, 2, 3, 4, 5]
print(len(my_list)) # Output: 5
To get the last element of a list, we can use negative indexing.
my_list = [1, 2, 3, 4, 5]
print(my_list[-1]) # Output: 5
They offer a handful of methods to manipulate the list, such as append(), insert(), remove(), pop(), count(), sort(), and reverse().
my_list = [1, 2, 3, 4, 5]
my_list.append(6)
print(my_list) # Output: [1, 2, 3, 4, 5, 6]
my_list.insert(2, 2.5)
print(my_list) # Output: [1, 2, 2.5, 3, 4, 5, 6]
my_list.remove(2.5)
print(my_list) # Output: [1, 2, 3, 4, 5, 6]
my_list.pop()
print(my_list) # Output: [1, 2, 3, 4, 5]
print(my_list.count(3)) # Output: 1
new_list = [3, 1, 4, 1, 5]
new_list.sort()
print(new_list) # Output: [1, 1, 3, 4, 5]
new_list.reverse()
print(new_list) # Output: [5, 4, 3, 1, 1]