Danh sách

A list holds many elements

• A list 列表 stores an ordered collection 有序集合 of values, called elements 元素, under one name.
• A single list colours might hold "red", "green", and "blue".
• One name replaces many separate variables.
• The order is fixed, so each element has a definite position.

Access by index

• You access or change an element using its index 索引 — its position in the list.
• In many languages the first element is at index $0$: colours[0] is "red".
• Read colours[1] to get "green", or assign to colours[2] to change it.
• Always check where a language starts counting.

A list holds many values in one variable, each found by its index

Traverse with a loop

• To process a whole list, use iteration to traverse 遍历 it.
• A loop visits every element in turn — first, second, third, and so on.
• The same loop works no matter how many elements the list holds.
• This is what makes list code so general 通用.

Change the contents

• Lists support operations that change their contents:
• append 追加 adds a new element to the end;
• insert adds an element at a chosen position; remove takes one out.