Summary

In this lesson, you learned that:

• A list stores several values, its elements, in one variable, in a fixed order: names = ["Anna", "Tom"]. An empty list is [].
• print(names) prints the list in square brackets, with commas, and with text in single quotes: ['Anna', 'Tom']. To print it with a label, use a comma or an f-string: print("Names:", names). Joining text and a list with + ends with a TypeError.
• Each element has an index, counted from 0. names[0] reads the first element, names[1] = "Lucy" changes the second one. Negative indexes count from the end: names[-1] is the last element. Asking for an index where there is no element ends with IndexError: list index out of range.
• The function len(names) gives you the number of elements. The last index is len(names) - 1.
• A method is a function that belongs to a value, written after a dot. append() adds an element to the end of a list. pop() removes the last element, or the one at the index in the parentheses, and returns it. remove() removes the first element with a given value; removing a value that isn't in the list ends with a ValueError.
• value in names is True if the list contains the value, and value not in names is True if it doesn't. Both are most often used with if.
• A list can contain other lists, called nested lists: groups[1][0] is the first element of the second inner list.
• A text isn't a list, but you can read its characters by index (name[0], name[-1]) and get its length with len(). You can't change its characters: name[0] = "X" ends with a TypeError.

In the next lesson, on loops, you'll learn to repeat code, for example to go through all the elements of a list one by one, however many there are. But first, practice what you know on a shopping list.