Python 简明教程
Python - Add List Items
Add List Items
在 Python 中添加列表项表示将新元素插入现有列表。列表是可变的，这意味着它们可以在创建后进行修改，从而可以添加、移除或修改它们的元素。
Adding list items in Python implies inserting new elements into an existing list. Lists are mutable, meaning they can be modified after creation, allowing for the addition, removal, or modification of their elements.
Adding List Items Using append() Method
Python 中的 append() 方法用于在列表的末尾添加单个元素。
The append() method in Python is used to add a single element to the end of a list.
我们可以通过在括号内指定我们要添加的元素来使用 append() 方法添加列表项，例如 my_list.append(new_item) ，它将 new_item 添加到 my_list 的末尾。
We can add list items using the append() method by specifying the element we want to add within the parentheses, like my_list.append(new_item), which adds new_item to the end of my_list.
Example
在以下示例中，我们使用 append() 方法在列表 “list1” 的末尾添加元素 “e”：
In the following example, we are adding an element "e" to the end of the list "list1" using the append() method −
list1 = ["a", "b", "c", "d"]
print ("Original list: ", list1)
list1.append('e')
print ("List after appending: ", list1)Output
以下是上面代码的输出： -
Following is the output of the above code −
Original list: ['a', 'b', 'c', 'd']
List after appending: ['a', 'b', 'c', 'd', 'e']Adding List Items Using insert() Method
Python 中的 insert() 方法用于在列表内的指定索引（位置）处添加元素，将现有元素移位以适应新的元素。
The insert() method in Python is used to add an element at a specified index (position) within a list, shifting existing elements to accommodate the new one.
我们可以通过在括号中指定要插入新项的索引位置和项本身来使用 insert() 方法添加列表项，例如 my_list.insert(index, new_item) 。
We can add list items using the insert() method by specifying the index position where we want to insert the new item and the item itself within the parentheses, like my_list.insert(index, new_item).
Example
在此示例中，我们有一个包含各种项的原始列表。我们使用 insert() 方法在特定位置将新元素添加到列表中：
In this example, we have an original list containing various items. We use the insert() method to add new elements to the list at specific positions −
list1 = ["Rohan", "Physics", 21, 69.75]
list1.insert(2, 'Chemistry')
print ("List after appending: ", list1)
list1.insert(-1, 'Pass')
print ("List after appending: ", list1)在向列表中追加 “Chemistry” 后，我们得到以下输出：
After appending 'Chemistry' to the list, we get the following output −
List after appending: ['Rohan', 'Physics', 'Chemistry', 21, 69.75]然后，在索引 “-1” 处（它最初指 69.75）插入 “Pass”，我们得到：
Then, by inserting 'Pass' at the index "-1", which originally referred to 69.75, we get −
List after appending: ['Rohan', 'Physics', 'Chemistry', 21, 'Pass', 69.75]我们可以看到 “Pass” 并未插入更新后的索引 “-1”，而是插入到之前的索引 “-1”。该行为是因为在向列表中追加或插入项时，Python 不会动态更新负索引位置。
We can see that "Pass" is not inserted at the updated index "-1", but the previous index "-1". This behavior is because when appending or inserting items into a list, Python does not dynamically update negative index positions.
Adding List Items Using extend() Method
Python 中的 extend() 方法用于将可迭代对象（如另一个列表）中的多个元素添加到列表末尾。
The extend() method in Python is used to add multiple elements from an iterable (such as another list) to the end of a list.
我们可以通过传递包含要添加的元素的另一个可迭代对象来使用 extend() 方法添加列表项，例如 my_list.extend(iterable) ，它将可迭代对象中的每个元素追加到 my_list 的末尾。
We can add list items using the extend() method by passing another iterable containing the elements we want to add, like my_list.extend(iterable), which appends each element from the iterable to the end of my_list.
Example
在以下示例中，我们使用 extend() 方法将 “another_list” 中的元素添加到 “list1” 末尾：
In the below example, we are using the extend() method to add the elements from "another_list" to the end of "list1" −
# Original list
list1 = [1, 2, 3]
# Another list to extend with
another_list = [4, 5, 6]
list1.extend(another_list)
print("Extended list:", list1)Output
上述代码的输出如下：
Output of the above code is as follows −
Extended list: [1, 2, 3, 4, 5, 6]