5.1. Data Structures in Python: Lists

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5.1. Data Structures in Python: Lists

Data structures are fundamental to computing and programming, as they allow us to efficiently organize and store data. In Python, one of the most versatile and used data structures are lists.

What are lists?

In Python, a list is a data structure that can contain multiple items, which can be of different types, such as numbers, strings, and even other lists. Lists are ordered, which means that the items have a defined order, and they are mutable, which means that we can add, remove, or change items after the list is created.

Creating lists

Creating a list in Python is simple. Just enclose the items in square brackets and separate them with commas. For example:

my_list = [1, 2, 3, 'Python', 'Django']

This list contains three numbers and two strings. But, as mentioned, lists can contain any type of data, and even other lists:

nested_list = [1, 2, ['Python', 'Django']]

Accessing list items

We can access items in a list by referring to the item's index. Indices in Python start at 0, so the first item has index 0, the second item has index 1, and so on. For example:

my_list = [1, 2, 3, 'Python', 'Django']
print(my_list[0]) # will print 1
print(my_list[3]) # will print 'Python'

If we try to access an index that doesn't exist, Python will give us an error. To avoid this, we can use the len() method to find out how many items there are in the list:

my_list = [1, 2, 3, 'Python', 'Django']
number_of_items = len(my_list) # will be 5

Adding and removing items

Since lists are mutable, we can add, remove, or change items. To add an item to the end of the list, we use the append() method. To add an item at a specific position, we use the insert() method. To remove an item, we use the remove() method, which removes the first occurrence of the item, or the pop() method, which removes the item at a specific index. For example:

my_list = [1, 2, 3, 'Python', 'Django']
my_list.append('new item') # now the list is [1, 2, 3, 'Python', 'Django', 'new item']
my_list.insert(0, 'first item') # now the list is ['first item', 1, 2, 3, 'Python', 'Django', 'new item']
my_list.remove(1) # now the list is ['first item', 2, 3, 'Python', 'Django', 'new item']
item_removed = my_list.pop(0) # now the list is [2, 3, 'Python', 'Django', 'new item'], and item_removed is 'first item'

Conclusion

Lists are a very powerful data structure in Python that allow us to efficiently store, access, and modify data. They are fundamental to many aspects of Python programming, and understanding how they work is essential for anyone who wants to become a competent Python programmer.

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165.2. Data Structures in Python: Tuples