Python Lists

In python, a list is a collection of items that can be of any data type; i.e. strings, numbers, etc. Lists are ordered and mutable, meaning that you can change the elements in a list after creating the list.

Creating a list
To create a list in Python, you can enclose a comma-separated sequence of values in square brackets []. For example:

numbers = [1, 2, 3, 4, 5]
names = ['Alice', 'Bob', 'Charlie']

Accessing elements
To access an element in a list, you can use its index in square brackets []. The first element in the list has an index of 0.

numbers = [1, 2, 3, 4, 5]
print(numbers[0]) # Output: 1
print(numbers[2]) # Output: 3

Modifying elements
To modify an element in a list, you can simply assign a new value to it using its index.

numbers = [1, 2, 3, 4, 5]
numbers[2] = 42
print(numbers) # Output: [1, 2, 42, 4, 5]

Adding elements
To add an element to a list, you can use the append method. This method adds an element to the end of the list.

numbers = [1, 2, 3, 4, 5]
numbers.append(6)
print(numbers) # Output: [1, 2, 3, 4, 5, 6]

Removing elements
To remove an element from a list, you can use the remove method. This method removes the first occurrence of the given value from the list.

numbers = [1, 2, 3, 4, 5, 6]
numbers.remove(3)
print(numbers) # Output: [1, 2, 4, 5, 6]

Sorting Python Lists

To sort a list in python, you can use the built-in 'sorted' function. By default, this function will sort the list in ascending order, but you can reverse the order by passing the argument 'reverse=True'.

numbers = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]
sorted_numbers = sorted(numbers)
print(sorted_numbers)
# Output: [1, 1, 2, 3, 3, 4, 5, 5, 5, 6, 9]

sorted_numbers = sorted(numbers, reverse=True)
print(sorted_numbers)
# Output: [9, 6, 5, 5, 5, 4, 3, 3, 2, 1, 1]

If you want to sort a list in-place, you can use the 'list.sort' method. This method sorts the list in-place and does not return a new list.

numbers = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]
numbers.sort()
print(numbers)
# Output: [1, 1, 2, 3, 3, 4, 5, 5, 5, 6, 9]

numbers.sort(reverse=True)
print(numbers)
# Output: [9, 6, 5, 5, 5, 4, 3, 3, 2, 1, 1]