A list holds several values in order, written in square brackets: scores = [8, 5, 9]. Lists can hold anything, including text and other lists, and they can grow and shrink.
Each item has a position called its index, and indexes start at 0, not 1. scores[0] is the first item, scores[2] the third. Negative indexes count from the end: scores[-1] is the last. len(scores) says how many items there are.
fruit = ["apple", "pear", "fig"]
print(fruit[0])
print(fruit[-1])
print(len(fruit))apple fig 3
Lists can change. append(x) adds x at the end, fruit[1] = "plum" replaces an item, remove(x) takes the first x out, and x in fruit asks whether it's there.
A slice takes part of a list: nums[1:3] gives the items at index 1 and 2 (it stops before 3, like range). Leave out a side to go to the end: nums[:2] is the first two, nums[2:] everything from index 2.
nums = [10, 20, 30, 40, 50]
print(nums[1:3])
nums.append(60)
print(len(nums), 30 in nums)[20, 30] 6 True
A for loop goes through a list item by item, which is how you total it or find the biggest. (Python also has sum(), max() and min() built in.)
What does this print?
days = ["Mon", "Tue", "Wed", "Thu"]
print(days[2])| [a, b, c] | A list. Indexes start at 0. |
|---|---|
| xs[i] / xs[-1] | The item at index i / the last item. |
| xs[a:b] | A slice: index a up to (not including) b. |
| len(xs) | How many items. |
| xs.append(x) | Adds x at the end. |
| x in xs | True if x is in the list. |